superseded publication

SUPERSEDED

PUBLICATION

This document has been superseded.

It should only be used for reference purposes.

For current guidance please visit the Austroads website:

www.austroads.com.au

http://www.austroads.com.au/

Guide to Road Tunnels Part 2: Planning, Design and Commissioning

Sydney 2019


Edition 2.1 prepared by: George Vorobieff and Les Louis Publisher Austroads Ltd. Level 9, 287 Elizabeth Street Sydney NSW 2000 Australia Phone: +61 2 8265 3300 [email protected] www.austroads.com.au

Edition 2.1 project manager: Richard Yeo

Abstract

The Guide to Road Tunnels Part 2 provides guidance to those making decisions in the planning, design, operation and maintenance of new road tunnels in Australia and New Zealand. Principles and standards identified are based on both Australasian and international experience.

Part 2 sets out the Austroads expectations regarding appropriate design for road tunnels. It discusses all aspects of planning, design and commissioning of road tunnels including structural and geotechnical requirements, fire and life safety, ventilation, lighting, traffic monitoring and control, plant monitoring and control, electrical power supply and the requirements for associated building structures.

It is expected that the Guide will be used by engineers and technical specialists in tunnel technology working on the planning, design and operation of road tunnels, proponents of road tunnel solutions, senior decision makers (in an overview role) and regulators in the various jurisdictions associated with the construction of tunnels.

About Austroads

Austroads is the peak organisation of Australasian road transport and traffic agencies.

Austroads’ purpose is to support our member organisations to deliver an improved Australasian road transport network. To succeed in this task, we undertake leading-edge road and transport research which underpins our input to policy development and published guidance on the design, construction and management of the road network and its associated infrastructure.

Austroads provides a collective approach that delivers value for money, encourages shared knowledge and drives consistency for road users.

Austroads is governed by a Board consisting of senior executive representatives from each of its eleven member organisations:

• Roads and Maritime Services New South Wales

• Roads Corporation Victoria

• Queensland Department of Transport and Main Roads

• Main Roads Western Australia

• Department of Planning, Transport and Infrastructure South Australia

• Department of State Growth Tasmania

• Department of Infrastructure, Planning and Logistics Northern Territory

• Transport Canberra and City Services Directorate, Australian Capital Territory

• The Department of Infrastructure, Regional Development and Cities

• Australian Local Government Association

• New Zealand Transport Agency.

Keywords

Tunnel characteristics, risk analysis, design criteria, structural requirements, geometric design, pavement design, noise, visual amenity, air quality, water quality, drainage, pollution control, fire safety, ventilation, lighting, electrical supply, monitoring and control, operations management and control, traffic management and control, communications, plant management and control, services buildings and plant rooms, construction issues, tunnel commissioning.

Edition 2.1 published March 2019

Edition 2.0 published November 2015

Edition 1.0 published November 2010 Edition 2.1 includes significantly expanded pavement design guidance in Section 5 and updated references to Austroads Guides throughout.

ISBN 978-1-925854-15-2

Austroads Project No. AAM2103

Austroads Publication No. AGRT02-19 Pages 125

© Austroads Ltd 2019

This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without the prior written permission of Austroads.

Acknowledgements Edition 1.0 and 2.0 prepared by: Les Louis. Edition 1.0 project managed by Ricky Cox and edition 2.0 by Mohamed Nooru-Mohamed. Cover image: Mullum Mullum Tunnel Victoria, supplied by EastLink

The authors acknowledge the role and contribution of members of the Austroads Road Tunnels Task Force and its invitees in providing guidance and information during the preparation of this guide.

This Guide is produced by Austroads as a general guide. Its application is discretionary. Road authorities may vary their practice according to local circumstances and policies. Austroads believes this publication to be correct at the time of printing and does not accept responsibility for any consequences arising from the use of information herein. Readers should rely on their own skill and judgement to apply information to particular issues.

mailto:[email protected]

mailto:[email protected]




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Contents

1. Introduction ............................................................................................................................................. 1 1.1. Structure of the Guide to Road Tunnels ................................................................................................... 1 1.2. Purpose of the Guide ............................................................................................................................... 1 1.3. Scope of the Guide to Road Tunnels Part 2 ............................................................................................ 2 1.4. Safe System ............................................................................................................................................. 2

2. General Design Requirements .............................................................................................................. 3 2.1. Road Tunnel Characteristics .................................................................................................................... 3 2.2. Overall Design Considerations ................................................................................................................. 3 2.3. Risk Analysis in the Planning and Design Stage ..................................................................................... 4

2.3.1. The Planning Phase .................................................................................................................. 5 2.3.2. The Design Phase .................................................................................................................... 5

2.4. Design Criteria .......................................................................................................................................... 6 2.4.1. Design Life and Optimum Life-cycle Cost ................................................................................. 6 2.4.2. Serviceability ............................................................................................................................. 7 2.4.3. Durability ................................................................................................................................... 8

2.5. Maintenance Requirements ................................................................................................................... 10 2.6. Design Methodology and Documentation .............................................................................................. 11 2.7. Design Validation during Construction ................................................................................................... 11

3. Structural Requirements ..................................................................................................................... 12 3.1. Introduction ............................................................................................................................................. 12

3.1.1. Role of the Structure ............................................................................................................... 12 3.1.2. Designing for Safe Construction and Use ............................................................................... 12 3.1.3. Additional Design Requirements............................................................................................. 12

3.2. The Support Function ............................................................................................................................. 13 3.3. Design for Fire and Fire Resistance ....................................................................................................... 14 3.4. Live Load Capacity ................................................................................................................................. 14

3.4.1. General ................................................................................................................................... 14 3.4.2. Permissible Development and Live Loading above the Tunnel and within the Easement Area

................................................................................................................................................ 15 3.4.3. Permissible Excavation within the Easement Area................................................................. 15 3.4.4. Vehicle-induced Wind-suction ................................................................................................. 15

3.5. Potential Surface Settlement due to Tunnelling ..................................................................................... 15 3.6. Tunnel Seismic Design ........................................................................................................................... 16

4. Geometric Design ................................................................................................................................. 17 4.1. General ................................................................................................................................................... 17 4.2. Sight Distance in Tunnels ....................................................................................................................... 17 4.3. Operating Speed .................................................................................................................................... 18 4.4. Horizontal Alignment .............................................................................................................................. 18 4.5. Vertical Alignment................................................................................................................................... 19

4.5.1. General ................................................................................................................................... 19 4.5.2. Vertical Curves ........................................................................................................................ 19 4.5.3. Grades .................................................................................................................................... 19


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4.6. Cross-section .......................................................................................................................................... 20 4.6.1. General ................................................................................................................................... 20 4.6.2. Lane Widths ............................................................................................................................ 20 4.6.3. Shoulder Widths ...................................................................................................................... 21 4.6.4. Crossfalls ................................................................................................................................ 21 4.6.5. Auxiliary Lanes ........................................................................................................................ 22 4.6.6. Emergency Stopping Lanes .................................................................................................... 22 4.6.7. Vehicle Refuges for Tunnel Incidents ..................................................................................... 22 4.6.8. Provision for Evacuation ......................................................................................................... 22 4.6.9. Emergency Equipment Cabinets ............................................................................................ 23 4.6.10. Escape Routes ........................................................................................................................ 23 4.6.11. Traffic Barriers ......................................................................................................................... 24 4.6.12. Working Width ......................................................................................................................... 24 4.6.13. Tunnel Envelope and Vehicle Clearance ................................................................................ 25

4.7. Ramp Connections/Diverges and Merges ............................................................................................. 26 4.8. Emergency and Maintenance Facilities.................................................................................................. 26

4.8.1. Vehicle Crossovers ................................................................................................................. 26 4.8.2. Turning Bays ........................................................................................................................... 27 4.8.3. Emergency Services Access and Parking .............................................................................. 27

5. Pavement Design.................................................................................................................................. 32 5.1. General ................................................................................................................................................... 32 5.2. Tunnel Structure and Pavement ............................................................................................................. 32 5.3. Health and Safety in Design ................................................................................................................... 35 5.4. Pavement Design Period ........................................................................................................................ 35 5.5. Design Traffic ......................................................................................................................................... 35 5.6. Pavement Wearing Surface ................................................................................................................... 36 5.7. Construction and Maintenance Considerations ..................................................................................... 37 5.8. Tunnel Environment ............................................................................................................................... 37 5.9. Subgrade Evaluation .............................................................................................................................. 38 5.10. Surface and Subsurface Drainage ......................................................................................................... 38 5.11. Pavement Materials ................................................................................................................................ 39 5.12. Design of Pavement ............................................................................................................................... 40

6. Environmental Considerations ........................................................................................................... 41 6.1. Noise ...................................................................................................................................................... 41

6.1.1. Tunnel-generated External Noise ........................................................................................... 41 6.1.2. In-tunnel Noise ........................................................................................................................ 41 6.1.3. Traffic Noise ............................................................................................................................ 42

6.2. Visual Amenity Considerations ............................................................................................................... 42 6.2.1. General Considerations .......................................................................................................... 42 6.2.2. Portal Design ........................................................................................................................... 42 6.2.3. Transition Zones ..................................................................................................................... 43 6.2.4. Internal Tunnel Design ............................................................................................................ 45 6.2.5. External Structures ................................................................................................................. 46

6.3. Air Quality ............................................................................................................................................... 48 6.3.1. Internal Tunnel Requirements ................................................................................................. 48 6.3.2. External Air Quality Requirements .......................................................................................... 48

6.4. Water Quality .......................................................................................................................................... 49

7. Drainage Design ................................................................................................................................... 50 7.1. General ................................................................................................................................................... 50 7.2. Drainage Systems .................................................................................................................................. 51

7.2.1. Overall Requirements ............................................................................................................. 51 7.2.2. Sumps, Separators and Pumping Stations ............................................................................. 52 7.2.3. Pumping Plant ......................................................................................................................... 53 7.2.4. Discharge Piping ..................................................................................................................... 54 7.2.5. Safety Requirements in Sumps .............................................................................................. 54


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7.3. Watertable Requirements ....................................................................................................................... 55 7.4. Pollution Control ..................................................................................................................................... 55 7.5. Calculation of Inflows.............................................................................................................................. 56

7.5.1. General ................................................................................................................................... 56 7.5.2. Rainfall and Stormwater Run-off ............................................................................................. 56 7.5.3. Ground Water .......................................................................................................................... 56 7.5.4. Wall Washing .......................................................................................................................... 57 7.5.5. Accidental Spillage .................................................................................................................. 57 7.5.6. Fire Suppression System ........................................................................................................ 57 7.5.7. Accidental Rupture of Pumped Drainage ............................................................................... 57 7.5.8. Flood Protection ...................................................................................................................... 57 7.5.9. External Hydraulic Impacts ..................................................................................................... 58

7.6. Aquaplaning ............................................................................................................................................ 58

8. Fire Safety ............................................................................................................................................. 59 8.1. Overall Approach .................................................................................................................................... 59 8.2. Design Development .............................................................................................................................. 60

8.2.1. General Approach ................................................................................................................... 60 8.2.2. Prevention ............................................................................................................................... 60 8.2.3. Evacuation .............................................................................................................................. 60

9. Ventilation Design ................................................................................................................................ 63 9.1. General ................................................................................................................................................... 63

9.1.1. Overall Requirements ............................................................................................................. 63 9.1.2. Assessing Ventilation Needs .................................................................................................. 63 9.1.3. Mechanical Ventilation ............................................................................................................ 63 9.1.4. Performance Objectives .......................................................................................................... 64 9.1.5. Factors Affecting Ventilation System Performance ................................................................ 64

9.2. Systems of Tunnel Ventilation ................................................................................................................ 65 9.3. Air Quality Management ......................................................................................................................... 65

9.3.1. Internal Tunnel Requirements ................................................................................................. 65 9.3.2. External Air Quality ................................................................................................................. 65

9.4. Fans ........................................................................................................................................................ 69 9.4.1. Noise ....................................................................................................................................... 71 9.4.2. Ventilation System Safeguards ............................................................................................... 72

10. Lighting Design .................................................................................................................................... 73 10.1. Overview ................................................................................................................................................. 73 10.2. Lighting Zones ........................................................................................................................................ 74 10.3. Spacing and Location of Luminaires ...................................................................................................... 74

10.3.1. General ................................................................................................................................... 74 10.3.2. Centrally Mounted Luminaires ................................................................................................ 74 10.3.3. Side Mounted Luminaires ....................................................................................................... 75 10.3.4. Visual Flicker ........................................................................................................................... 75

10.4. Surface Reflectance ............................................................................................................................... 75 10.5. Other Requirements ............................................................................................................................... 77

10.5.1. Essential Lighting Supply ........................................................................................................ 77 10.5.2. Emergency and Egress Passage Lighting .............................................................................. 77 10.5.3. Luminaire Enclosures ............................................................................................................. 77 10.5.4. Lighting Control ....................................................................................................................... 78 10.5.5. Future Developments .............................................................................................................. 78


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11. Electrical Supply Design ..................................................................................................................... 79 11.1. General ................................................................................................................................................... 79 11.2. Tunnel Electrical Supply System ............................................................................................................ 79

11.2.1. General ................................................................................................................................... 79 11.2.2. Security of Supply ................................................................................................................... 80 11.2.3. Design and Maintenance ........................................................................................................ 80 11.2.4. Electromagnetic Fields Minimisation....................................................................................... 81

11.3. High Voltage System .............................................................................................................................. 81 11.4. Low Voltage System ............................................................................................................................... 81

11.4.1. Protection Systems ................................................................................................................. 81 11.5. Uninterruptible Power Supply ................................................................................................................. 82

11.5.1. General ................................................................................................................................... 82 11.5.2. Essential Loads Network ........................................................................................................ 82 11.5.3. Types of UPS .......................................................................................................................... 82 11.5.4. UPS Design Parameters ......................................................................................................... 82 11.5.5. Back-up Generating Equipment .............................................................................................. 83

11.6. Cabling ................................................................................................................................................... 83

12. Design for Monitoring and Control ..................................................................................................... 84 12.1. Operations Management and Control Systems ..................................................................................... 84

12.1.1. Introduction ............................................................................................................................. 84 12.1.2. Operator Interface ................................................................................................................... 85 12.1.3. Response Procedures ............................................................................................................ 85 12.1.4. Trainer and Back-up System .................................................................................................. 85 12.1.5. Report and Logging Requirements ......................................................................................... 85 12.1.6. Reliability and Availability ........................................................................................................ 86 12.1.7. Performance Requirements .................................................................................................... 86 12.1.8. Scope for Future Development of the OMCS ......................................................................... 87

12.2. Tunnel Control Centre ............................................................................................................................ 87 12.3. Traffic Monitoring and Control System ................................................................................................... 88

12.3.1. General ................................................................................................................................... 88 12.3.2. Tunnel Information Signs System ........................................................................................... 88 12.3.3. Lane Control System .............................................................................................................. 89 12.3.4. Variable Speed Limit (VSL) System........................................................................................ 89 12.3.5. Ramp Control Signs System ................................................................................................... 90 12.3.6. Variable Message Signing System ......................................................................................... 90 12.3.7. Tunnel Closures ...................................................................................................................... 90 12.3.8. Remotely Controlled Barriers .................................................................................................. 93 12.3.9. Traffic Monitoring .................................................................................................................... 93 12.3.10. Closed Circuit Television ........................................................................................................ 94 12.3.11. Automatic Incident Detection .................................................................................................. 95

12.4. Directional Signing System .................................................................................................................... 95 12.5. Communications System ........................................................................................................................ 96

12.5.1. General ................................................................................................................................... 96 12.5.2. Radio Re-broadcast ................................................................................................................ 96 12.5.3. Emergency Services Communications ................................................................................... 97 12.5.4. Public Address System ........................................................................................................... 97 12.5.5. Help Phones/Motorist Emergency Telephone System ........................................................... 97 12.5.6. Mobile Telephones Re-broadcast ........................................................................................... 97

12.6. Plant Management and Control System................................................................................................. 97 12.7. Tunnel Network Communication System ............................................................................................... 98


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13. Services Buildings and Plant Rooms ................................................................................................. 99 13.1. General ................................................................................................................................................... 99 13.2. Design and Layout.................................................................................................................................. 99

13.2.1. Space and Provision Requirements........................................................................................ 99 13.2.2. Cable and Equipment Separation ......................................................................................... 100 13.2.3. Future Maintenance .............................................................................................................. 100

13.3. Heating, Ventilation and Air Conditioning ............................................................................................. 100 13.4. Floor Loading ........................................................................................................................................ 100 13.5. Lightning Protection .............................................................................................................................. 100 13.6. Building Security and Fire Protection ................................................................................................... 100

13.6.1. Intruder Alarm System .......................................................................................................... 100 13.6.2. Fire Alarm and Extinguishing Systems ................................................................................. 100

14. Construction Issues ........................................................................................................................... 101 14.1. Overview ............................................................................................................................................... 101 14.2. Responsibility of Designers .................................................................................................................. 102 14.3. Design Review for Construction ........................................................................................................... 103 14.4. Ventilation System for Construction ..................................................................................................... 103 14.5. Design Review for Construction ........................................................................................................... 104 14.6. Ventilation System for Construction ..................................................................................................... 104

15. Tunnel Commissioning ...................................................................................................................... 107 15.1. General ................................................................................................................................................. 107 15.2. The Commissioning Plan ..................................................................................................................... 107

15.2.1. Overall Requirements ........................................................................................................... 107 15.2.2. Personnel .............................................................................................................................. 107 15.2.3. Testing and Commissioning Protocol ................................................................................... 108 15.2.4. Acceptance Criteria ............................................................................................................... 108 15.2.5. Corrective Actions ................................................................................................................. 108 15.2.6. Documentation ...................................................................................................................... 108

15.3. Testing and Commissioning of System Components .......................................................................... 108 15.3.1. Overall Requirements ........................................................................................................... 108 15.3.2. Fire Safety System ................................................................................................................ 109 15.3.3. Ventilation System Validation ............................................................................................... 109 15.3.4. Electrical Supply Validation ................................................................................................... 110 15.3.5. Lighting System Validation .................................................................................................... 111 15.3.6. Drainage Validation ............................................................................................................... 111 15.3.7. System Integration ................................................................................................................ 111

15.4. Commissioning Records ...................................................................................................................... 111 15.4.1. General ................................................................................................................................. 111 15.4.2. Inspection Checklists ............................................................................................................ 112 15.4.3. As-built Records .................................................................................................................... 112 15.4.4. Manuals Required ................................................................................................................. 112

15.5. Operational Readiness ......................................................................................................................... 114 15.5.1. General ................................................................................................................................. 114 15.5.2. Infrastructure Readiness ....................................................................................................... 114 15.5.3. Personnel Readiness ............................................................................................................ 114 15.5.4. Documentation Readiness .................................................................................................... 115

15.6. Continuous Improvement ..................................................................................................................... 115

References .................................................................................................................................................... 116 Horizontal Curves and Sight Distance .............................................................................. 121 General Classification of Ventilation Systems ................................................................ 123


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Tables

Table 9.1: Distances over which jet fans may be considered destroyed during fire ..................................... 71 Table 12.1: Performance requirements ........................................................................................................... 86

Figures

Figure 4.1: Identifying the escape route (CityLink tunnel, Melbourne) ........................................................... 23 Figure 4.2: Exit ramps in tunnels .................................................................................................................... 28 Figure 4.3: Exit ramps – major diverge and secondary exit on a ramp in tunnels ......................................... 29 Figure 4.4: Entry ramps in tunnels ................................................................................................................. 30 Figure 4.5: Branch connections in tunnels ..................................................................................................... 31 Figure 5.1: Typical cross-section of a drained mined tunnel and the pavement is placed onto the

floor of the tunnel ......................................................................................................................... 33 Figure 5.2: A mined tunnel under construction with the walls and ceiling being tanked before

concrete is placed ........................................................................................................................ 33 Figure 5.3: A circular (left) and elliptical (right) tunnel cross-section with common backfill profiles .............. 34 Figure 5.4: Cross-section of a no cell and centre cell immersed tube tunnel where the floor of

the tunnel becomes the pavement ............................................................................................... 34 Figure 5.5: Typical section through a cut-and-cover tunnel with a thick reinforced concrete

pavement ...................................................................................................................................... 35 Figure 5.6: View of a wet patch and staining from a water leak occurring from the ceiling of the

tunnel ............................................................................................................................................ 37 Figure 5.7: All surface drainage pit covers should be located in the shoulder and not in the

trafficable lane .............................................................................................................................. 39 Figure 5.8: Typical pavement profile of CRCP base layer, AC7 asphalt interlayer and no fines

concrete subbase for drained tunnel ............................................................................................ 40 Figure 6.1: Portal and transition design – EastLink tunnel, Victoria ............................................................... 43 Figure 6.2: Entrance to Heysen tunnels – South Australia ............................................................................ 44 Figure 6.3: Entrance to the Lane Cove tunnel – Sydney ............................................................................... 44 Figure 6.4: Typical tunnel interior ................................................................................................................... 46 Figure 6.5: Cross-city tunnel ventilation Sydney ............................................................................................ 47 Figure 6.6: Lane Cove tunnel ventilation Sydney ........................................................................................... 47 Figure 9.1: ‘Idealised’ concentration profile in a longitudinal ventilated tunnel (reality may be

substantially more complex) ......................................................................................................... 66 Figure 9.2: Illustrative schematic of an outlet near an exit portal ................................................................... 67 Figure 9.3: Example of multiple outlets for air exchange system ................................................................... 68 Figure 9.4: Schematic example of slots in the roof, including sound attenuators .......................................... 68 Figure 9.5: Natural ventilation by using large gaps ........................................................................................ 69 Figure 9.6: Natural ventilation by using small repeating gaps in the roof ...................................................... 69 Figure 10.1: The zones in a long tunnel ........................................................................................................... 74 Figure 10.2: Example of light reflected from wall and road surfaces ............................................................... 76 Figure 10.3: Light distribution ........................................................................................................................... 76 Figure 12.1: An example of a tunnel closure treatment utilising boom gates, signals and signs ..................... 92 Figure 12.2: Tunnel closures – signal aspects ................................................................................................. 93 Figure 14.1: Tunnel under construction (CityLink tunnel, Melbourne) ........................................................... 102 Figure 14.2: Tunnel boring machine – Clem 7 tunnel .................................................................................... 105


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1. Introduction

1.1. Structure of the Guide to Road Tunnels

The Guide to Road Tunnels is written in three Parts:

• Part 1: Introduction to Road Tunnels

• Part 2: Planning, Design and Commissioning

• Part 3: Operation and Maintenance.

While the total document has been separated into three parts, there is considerable inter-dependence between the Parts and appropriate cross-references have been made where necessary. For example, in designing road tunnels, the scope determined in the planning must be recognised and the way the tunnel will be constructed and operated and how it will be maintained will be important inputs to design decisions.

1.2. Purpose of the Guide

The document provides guidance to those making decisions in the planning, design, operation and maintenance of new road tunnels in Australia and New Zealand. Principles and standards identified are based on experience both in Australasia and in other countries where tunnels have been constructed over a long period of time. Practices referred to in other countries have been considered in the light of Australasian experience and adopted (where appropriate), cognisant of Australasian conditions and legislation.

It is expected that the Guide will be used by engineers and technical specialists in tunnel technology working on the planning, design and operation of road tunnels, proponents of road tunnel solutions, senior decision makers (in an overview role) and regulators in the various jurisdictions associated with the construction of tunnels.

It is intended that users of this Guide will be able to determine standards for road tunnel design and operation acceptable to Austroads members, either directly from the Guide or from other references defined by the Guide as providing the appropriate standards for adoption. Planners, designers and operators will be able to ascertain the range of factors to be considered and use the defined standards to produce an acceptable design. Senior decision makers will be able to determine the range of factors to be considered and from that assess whether the proposal will meet the requirements of the Austroads members.

In reaching a conclusion on the acceptable requirements for a particular tunnel, designers should use a risk-based approach to justify the parameters to be used. This approach will need to consider the issues involved and the range of values for a parameter that will satisfy the identified issues.



1.3. Scope of the Guide to Road Tunnels Part 2

This Part of the Guide to Road Tunnels sets out the Austroads expectations regarding appropriate design for road tunnels. It discusses all aspects of the planning, design and commissioning of road tunnels including structural and geotechnical requirements, fire and life safety, ventilation, lighting, traffic monitoring and control, plant monitoring and control, electrical power supply and the requirements for associated building structures.

This Part of the Guide also:

• Discusses the expected approach to the design of the elements of the tunnel project and where appropriate defines acceptable standards for those elements. It should be regarded as the benchmark for the planning and design of new road tunnels in Australia and New Zealand. Emphasis is placed on adopting a risk management approach to the design of the elements, stressing the importance of considering the interaction of the various components and the effect of the total combination of the elements.

• Defines the requirements for commissioning of road tunnels, the effect this has on design and the documentation required to ensure that all systems are functioning appropriately before operation commences.

Part 2 does not deal with the refurbishment of existing tunnels or the retro-fitting of components to existing tunnels. However, for projects of that nature, the discussions in this Part may be of assistance in deciding on the appropriate design to adopt having regard to the factors involved and the economy of the possible solutions.

The technology for tunnel design and operation is continually developing and the Guide will be updated to reflect this development.

It should be understood that for such a wide and developing topic, the guidance provided should not be considered as exhaustive. It is not intended to provide any form of substitute for the specialist expertise that is needed to prepare effective and efficient working designs for a road tunnel.

1.4. Safe System

The Guide to Road Tunnels should be considered in the broad context of road safety and the contribution that the Guide can make to the design of safer roads. Safe System principles are acknowledged in the National Road Safety Action Plan 2009 and 2010 as the guiding principles for road safety programs in Australia.

The Austroads approach to Safe System design is set out in the Guide to Road Tunnels Part 1: Introduction to Road Tunnels (Austroads 2018a).



2. General Design Requirements

2.1. Road Tunnel Characteristics

Road tunnels have a number of distinguishing characteristics such as:

• an enclosed space with horizontal, lateral and vertical visual restrictions

• may be speed restricted

• changed driver perceptions

• the absence of parked vehicles, roadside obstacles, cyclists and pedestrians

• controlled environment (e.g. illumination, ventilation)

• extensive fire and life safety features.

However, tunnels exhibit a better accident record than the open road due to a combination of factors such as:

• drivers becoming more alert in the changed environment of the tunnel

• absence of roadside obstacles

• standard of construction

• extensive safety features (traffic controls and fire and life safety).

2.2. Overall Design Considerations

It will be necessary to comply with a range of specific standards and codes for many of the elements of tunnel design (e.g. tunnel fire safety; lighting; electrical works; building code in NZ). In addition, various Austroads Guides, international standards, World Road Association (PIARC), European Union and other publications provide considerable reference and guidance material.

Some general design considerations are:

• structural requirements

• seismic loadings

• over-height vehicles (appropriate to the road corridor)

• breakdown bays

• providing for pedestrians, and the mobility impaired (including evacuation requirements)

• design vehicle to be adopted

• dangerous goods movements

• combustible goods movements

• operating speed

• cross-section elements

• grading

• drainage

• fire and life safety

• ventilation



• lighting

• communications

• electrical requirements

• operations management and control system (OMCS) requirements to suit the particular tunnel, its associated road network and the communications with any central traffic management centre in the jurisdiction concerned (includes operating the deluge system, implementing traffic management plans and reporting faults to the asset management system) (refer to Part 3).

Whether a tunnel should allow the free passage of dangerous goods vehicles (placarded vehicles) operating within the law should be determined through a risk management approach and involve all relevant stakeholders. One consideration is that diverting such vehicles off the major road system could transfer risk to locations that may not have facilities or ready access to deal with any emergency incident involving fire or spillage.

The OECD (2001) report Transport of Dangerous Goods through Road Tunnels provides a quantitative risk assessment model (QRAM). The model is claimed to be applicable to all countries. The report states:

The transport of dangerous goods through tunnels implies special risks to road users, physical structures, environment and people residing near tunnels or detour roads. Transport authorities have to decide whether dangerous goods transport is permitted on certain routes or not. If permitted, the safest and most practical manner for transporting these dangerous goods has to be decided. QRAMs can assist decision makers by providing risk estimates that are both accurate and objective for different types of dangerous goods, tunnels and transport scenarios.

Further guidance on using such a quantitative risk assessment model may be obtained in PIARC (2012a).

During the concept phase a design standards report may be required to set out for a particular tunnel project the key road and tunnel design parameters selected. The level of detail depends on the project characteristics and level of complexity. For short tunnels this may consist of nothing more than a reference to the Guide and a summary appendix of geometric design criteria.

Longer and more complex tunnels will require a detailed design standards report documenting the derivation and selection of those criteria. This report should be updated regularly as the project progresses. Which features to include will depend on a range of factors including the length of the tunnel and the traffic volume expected. Some guidance on fire safety is provided in AS 4825: 2011 Tunnel Fire Safety. It is important to tailor the design to the specific requirements of the particular tunnel and avoid over-specifying features that are not necessary for those circumstances.

Mashima and Mizutani (2003) describe a classification system used in Japanese tunnels. This may provide general guidance to practitioners on what facilities may be required in a specific tunnel under consideration.

2.3. Risk Analysis in the Planning and Design Stage

The principles of risk analysis and management are described in the Guide to Road Tunnels Part 1: Introduction to Road Tunnels (Austroads 2018a) and Risk Analysis for Road Tunnels (PIARC 2008a). These principles apply to risk analysis and management in the planning and design phase.



2.3.1. The Planning Phase

The planning phase includes feasibility studies, concept development, site and geotechnical investigations (refer to Appendix A of Guide to Road Design Part 2: Design Considerations (Austroads 2019b), development and evaluation of project options and any design studies to finalise the preferred option and selection of a delivery method. It is essential that sufficient time is allowed to investigate and demonstrate the technical viability of a project prior to proceeding to tender stage and if necessary prepare designs appropriate to the form of contract to be adopted.

Risk assessment and evaluation of options should take into account:

• the geology and hydrogeology of the site

• tunnelling techniques appropriate to the nature of the ground and environment and the selected alignment options

• temporary and permanent ground support systems

• ground and ground water treatment measures, their impact on the environment and on third parties

• ground movements and settlements at the ground surface, their impact on a third party or subsurface ground movements and their impact on buried structures such as utility services, adjacent tunnels and underground structures

• environmental considerations including dust, noise, vibrations, traffic, construction equipment movements

• associated costs

• health, safety and program implications

• appropriate forms of contract

• hazardous materials including gases, chemicals, other pollutants or naturally occurring substances that could be detrimental to health or affect durability

• functional safety of electrical systems

• operations and maintenance requirements

• all other particular factors relevant to the proposed project location, geology and environment.

Risk assessments and evaluations should include identifying and evaluating the hazards and consequent risks of all of the options and documenting them formally. The risk register should be continually reviewed and revised to take account of the results of investigations and further and better information that becomes available through the project development process.

2.3.2. The Design Phase

The fundamental objective of the design process is to achieve a design where the risk of failure or damage to the tunnel works or to a third party from all reasonably foreseeable causes, including health and safety considerations, is acceptably low during the construction and design life of the tunnel works. High consequence but low frequency events that could affect the works or a third party are also to be considered (International Tunnelling Insurance Group 2012).

Designers should:

• undertake a comprehensive risks/safety analysis as an aid to determine the most appropriate mix of design response and operations procedures (safety-in-design concepts must be included)

• provide monitoring and control systems that allow incidents to be detected and responded to in order to minimise harm to people, damage to the tunnel structure and traffic disruption.



The objective is to design out as many risks as practicable and to provide systems to minimise reliance on human processes/procedures where practicable.

It is necessary to:

• identify potential risks

• assess the causes

• determine the consequences

• provide strategies to minimise risks

• provide solutions that mitigate consequences

• undertake formal functional safety assessment of all electrical, electronic and programmable electronic systems.

Factors to consider include:

• design requirements and criteria

• geotechnical issues (including seismic effects)

• intermediate stages of construction

• sensitivity of

– construction tolerances

– variation in geotechnical design values

– variation in material characteristics

– variation in workmanship and geometry

– variation in methods of construction and the implementation of mitigation/contingency measures

– natural perils exposure in the region of the project such as flood, storm, seismic or tidal effects

• potential failure of systems/processes

• extent of design checks

• constructability issues.

Appropriate references include AS/NZS ISO 31000: 2009: Risk Management: Principles and Guidelines, Australasian Fire and Emergency Service Authorities Council (2001): Fire Safety Guidelines for Road Tunnels, PIARC (2013): Risk Evaluation, Current Practice for Risk Evaluation for Road Tunnels, International Tunnelling Insurance Group (2012): A Code of Practice for Risk Management of Tunnel Works, and AS 4825: 2011: Tunnel Fire Safety.

2.4. Design Criteria

2.4.1. Design Life and Optimum Life-cycle Cost

The design life to be adopted for various elements in the tunnel structure and ancillary infrastructure should be determined during the planning of the tunnel. Specific assessment of the required design life of each element in the tunnel infrastructure should be made and the optimum outcome determined. In determining the optimum outcome, the likely replacement cycle for products and the cost involved in achieving that cycle should be considered together with the operation and maintenance costs.



Unless otherwise specified, the following design life for the various elements should be adopted:

• permanent structural elements – 100 years

• tunnel drainage – 100 years

• temporary structural elements – 5 years

• fans, dampers and attenuators – 25 years

• tunnel lights and sensors

– lamps 3–4 years

– batteries 5–7 years

– lighting controllers 10 years

• luminaires, signage and other electrical equipment housings and supports – 15 years

• pumps – 10 years (fire pumps and other non-submersible installations with few running hours per year may have a longer life)

• diesel generators – 15–20 years

• control systems and sensors (hardware and software)

• industrial processors and peripherals (PLC) – 10 years

• central/back office servers and hardware and operating system (OS) – 5 years

• application software – 10 years

• cabling – 25 years

• electrical equipment

– high voltage (HV) and low voltage (LV) switchboards, transformers – 15–20 years

– static industrial electronics (protection relays, uninterruptible power system (UPS)) – 10–15 years.

A change to the design life of a specific element may be considered if it can be demonstrated that the life-cycle cost can be enhanced by adopting a suitable variation. When determining the design life of any element, consideration should be given to the impact of that element on other elements during replacement of that element (e.g. potential impact on a waterproofing membrane).

PIARC (2012b) provides a methodology for determining the design life of electrical equipment. This methodology may be of assistance in establishing a more rigorous assessment of the design life of these components.

2.4.2. Serviceability

Serviceability refers to the ability of the infrastructure to perform satisfactorily and safely over the life of the infrastructure, and includes the following matters:

• The integrity of the tunnel structure and its linings – cracking should be limited and no sections of the linings should be dislodged during operation.

• Water should not be allowed to drip from the roof or walls onto the roadway.

• Drainage water should not encroach onto the running surface.

• Equipment should not be dislodged from its fixed site (in particular, overhead equipment) – chemical anchors may be used provided they are not subject to long term creep and have the appropriate fire response.

• Systems should operate in accordance with the agreed protocols.

• Ease of access for personnel for maintenance of the various tunnel components and equipment.



2.4.3. Durability

General

The design for durability of the tunnel structure and its associated elements will be determined by a combination of factors including the tunnel profile, the material types considered for the structural support and the working environment both within the tunnel and from the surrounding ground, and the ground water regime (both physical and chemical).

The necessity for waterproofing and whether the tunnel is drained or undrained (fully tanked) will also influence the final tunnel support solution. Repeated wetting and drying of the inner lining surface can lead to a breakdown of the surface of the concrete. The degree of wetting and drying will determine the need for waterproofing of the tunnel to overcome this problem.

Future building development around a tunnel may also be a long-term consideration as the tunnel lining may have to accommodate increased stresses from either ground elevation (basement excavation) or an imposed load from a future building foundation if the load is not transferred past the tunnel. Specific design criteria for the building may have to be issued to developers.

Durability requirements should be based upon the following exposure categories:

• Metal items in tunnel: AS/NZS 2312: 2002; Category D – High.

• Concrete items generally: AS 5100.5: 2004; Category, minimum B2.

• Concrete elements in contact with saline water: AS 5100.5: 2004; Category C.

In New Zealand, concrete durability is defined in NZS 3101.1&2: 2006: Concrete Structures Standard.

Tunnel design and construction in New Zealand is subject to the requirements of the New Zealand Building Code.

Alternative structural support methods

There are several alternative structural support systems for tunnels which can be applied alone or in combination with other types. An outline of each type is provided below.

Permanent rock bolts

Permanent rock bolts have been used extensively in Australian road tunnels. There are various international standards and guidelines that could be incorporated into the tunnel specification (see references). Installation and testing recommendations of the rock bolt supplier may also be applicable.

Generally, permanent rock bolts consist of a fully grouted bolt length in combination with a polyethylene sheath. Quality assurance of installation should include verification that the grout will consistently fully encapsulate the rock bolt. The end nut and bearing plate must be fully protected from the environment. This may include embedment in either shotcrete or concrete. Rock bolts may also be made of stainless steel (using one of the 316 stainless steel grades) in which case sheathing may not be required. For lighter loads, fibreglass rock bolts may also be considered as permanent support in selected locations.



Segmental concrete linings

High quality precast concrete segmental linings are erected in the tail shield of tunnel boring machines (TBMs). They can be reinforced with either polypropylene or steel fibres or steel reinforcement. The temporary jacking loads used to push the TBM forward off the last erected segmental ring are often the highest loads the segments will experience. Gaskets at the segment joints seal the tunnel from water ingress and are generally made of a hydrophilic material or rubber. Some gasket profiles combine the two materials in separate strips in the one gasket.

Unreinforced in situ concrete

Unreinforced concrete arch profile tunnels are very often used for road tunnels. Staged pressure grouting of the lining is generally required to fill voids. Any cracks in the concrete should also be repaired. The criteria for grouting and concrete crack repair should be included in the tunnel lining specifications. There is an increasing use of fibres in concrete linings and apart from polypropylene fibres reducing concrete spalling under fire conditions, steel fibres can also serve as structural reinforcement. An arched profile with no, or minimal, bending moments can be used to reduce crack widths due to shrinkage. Surface rusting of exposed steel fibres can occur, but because the fibres are not continuous throughout the concrete mass they provide a durable alternative to steel reinforcement.

Where a continuous membrane is not used, the construction joints between concrete pours require particular attention to prevent water leakage. Hydrophilic strips and green cutting of the concrete are two methods that may be considered.

Reinforced concrete

Steel reinforced concrete design for tunnel linings should refer to the most appropriate concrete code. These may include the bridge code AS 5100 Set-2007 (required for 100-year design life) or the concrete code AS 3600:2009 (applicable for a 50-year design life). Additional measures such as increased reinforcement cover or increased concrete quality may have to be considered to achieve the required design life. Equivalent New Zealand standards are NZS 3101.1&2: 2006: Concrete Structures Standard and NZ Transport Agency (2013a): Bridge Manual (3rd edition).

Shotcrete linings

Permanent shotcrete linings are increasingly being accepted as permanent support in tunnels. While Sydney, for example, has numerous road tunnels supported by a combination of permanent rock bolts and shotcrete, there is an increasing international trend to use shotcrete alone if the tunnel section is an appropriate arched profile. Shotcrete in this application is commonly used in combination with a spray-on membrane to ensure a drip-free environment within the tunnel or alternatively to achieve a fully tanked tunnel. The shotcrete may be plain or fibre reinforced (either polypropylene or steel fibres).

There are several issues regarding the practical application of spray-on membranes. The most important issue is the ability to apply the membrane when ground water seepage is present.

Channelling the water may be required before applying the membrane. Alternatively, where possible, it is more desirable to use epoxy injection methods at the site of the water leakage to provide a dry surface prior to applying the spray-on membrane.

Buried structures

Buried structures require specific design consideration that depends upon the ground conditions. Ground anchors should be designed and installed in accordance with BS 8081: 1989: Code of Practice for Ground Anchorages; BS EN 1537: 2013: Execution of Special Geotechnical Work – Ground Anchors, BS 8006-1: 2010: Code of Practice for Strengthened/Reinforced Soils and other Fills and BS 8006-2: 2011: Code of Practice for Strengthened/Reinforced Soils and other Fills, Soil Nail Design.



Piles should be designed to the requirements of the Australian piling code (AS 2159: 2009). This code has requirements for sacrificial thickness when using steel piles and for both cover and mix design for concrete piles. In New Zealand, the following guides and specifications are applicable: Auckland Structural Group (2002): Piling Specification, and Institution of Civil Engineers (2007): Specification for Piling and Embedded Retaining Walls.

All structures should be designed and constructed with a monitoring system and if not installed initially, designed to allow a cathodic protection system to be readily implemented or installed at a later date if ground conditions warrant such protection.

Steel members

Appropriate protection for steel members should be determined as follows:

The tunnel environment should be considered as a humid, contaminated, environment. Durability requirements should be designed in accordance with AS/NZS 2312: 2002; High end Category C.

The ventilation station environment should be considered as a damp contaminated environment exposed to outdoor conditions. Durability requirements should be designed in accordance with AS/NZS 2312: 2002; Category D – High.

Overhead fasteners

The ability of overhead fasteners to withstand the weight of the facilities (e.g. jet fans) under all conditions, including fire, should be considered. Adhesive anchors should not be used unless an analysis of embedment has determined that the thermodynamics of fire heat transfer of the adhesive are suitable and can withstand the effects of the design fire. Correctly specified adhesive anchors should not suffer from creep and should have an adequate design life.

Other tunnel components

Materials to be used for electrical and mechanical equipment, fire resistant coatings and claddings should be designed in accordance with sound materials engineering principles and certified in accordance with the appropriate standards as to their fitness for purpose and appropriateness for the design life expected of those components. For the surface reflectance requirements for linings, refer to Section 10.4.

2.5. Maintenance Requirements

The design should consider the implications for the maintenance task in all aspects of the tunnel infrastructure and its operation. Choice of the appropriate equipment and its location can have a marked effect on the ease and safety with which maintenance activities can be carried out. In addition, the operation of the tunnel can be more efficient with fewer disruptions when the maintenance activities can be carried out clear of traffic. A service tunnel should be considered to carry out routine maintenance activities in order to achieve this.

It is essential that maintenance can be undertaken safely with minimum disruption to traffic. If a maintenance activity cannot be safely executed with traffic in the tunnel, the tunnel must be closed partially or totally depending on the circumstances. It is therefore desirable that designers determine the elements of the tunnel design with the maintenance requirements in mind. This can be applied to the items of equipment and to the location of equipment and facilities with the objective of minimising the need for maintenance or removing the maintenance task from the traffic in the tunnel.

Consideration should also be given to the impacts of maintenance on systems, particularly those providing functional safety solutions.



Where appropriate, the maintenance issues involved with a specific part of the tunnel design are discussed in the relevant sections of this document. Specific situations are discussed in:

• emergency and maintenance facilities – Section 4.8

• drainage systems – Section 7.2

• lighting fixtures – Section 10.3

• electrical systems – Section 11

• location of cables – Section 11.6

• signs and communication – Section 12.

2.6. Design Methodology and Documentation

The design methodology is to be documented and should include:

• A description of the element to be designed.

• The design requirements and criteria to be adopted.

• A geotechnical assessment that evaluates the geological and geotechnical information available (including the presence or generation of harmful gases, ground and ground water contamination) and ascribes values for the assessed ground and ground water conditions. This is done for the purpose of design with justification in the light of information provided (refer to the Guide to Road Tunnels Part 1 (Austroads 2018a). Available information may not be adequate to design the works. Experienced tunnel designers who can evaluate whether the information is sufficient for the purpose of tunnel design should be engaged to undertake such works. If additional information is required, then the scope of the required investigations should be established and appropriate allowances made for time and budget.

• A description of the method of design (including reference to any applicable codes or standard).

• A description of the method(s) of analysis to be used for the design and the justification thereof.

• The serviceability requirements and the ultimate loads used in the design.

• The maintenance issues arising from specific aspects of the design and how these have been addressed.

• A design risk assessment (Section 2.3).

• The checking procedure to be implemented for the design.

2.7. Design Validation during Construction

Designers should document the monitoring procedures to be adopted during construction to ensure that the design being implemented remains valid at all times. The monitoring required will include the performance of ground and ground water, the tunnel works structures, and adjacent structures potentially affected by the tunnel works.

Commissioning of the tunnel will include extensive integrated testing of all life safety systems (Section 15) with the early involvement of the tunnel operator and fire authority.



3. Structural Requirements

3.1. Introduction

3.1.1. Role of the Structure

The tunnel structure and other structures provided undertake a variety of roles, namely to:

• facilitate the transport function throughout the design life

• provide a defined level of support to the area surrounding the tunnel

• provide sufficient structural strength and robustness to ensure fire resistance and fire separation in the event of a fire

• facilitate maintenance activities throughout the life of the structure.

The first two functions ordinarily need an understanding of geotechnical conditions and imposed loads to ensure a durable tunnel structure. The third requires consideration of internal conditions to aid in the reduction of the conditions conducive to fire development, to enable detection and verification systems to function, to create appropriate separation between fire/smoke and safe areas, to prevent such safe areas becoming untenable and to prevent situations that may endanger emergency response personnel. The fourth requires an understanding of the implications of maintaining the structure, equipment and systems, which may be constrained after construction is completed.

3.1.2. Designing for Safe Construction and Use

Most jurisdictions in Australia and New Zealand require ‘safety in design’ to be applied to engineering work (Barker & Casey 2012; McMullan 2014). It applies to all stages in the life cycle of a project commencing with the inception stage, through the planning and design stages, followed by the construction and commissioning and ongoing operation and maintenance stages, and in certain cases, decommissioning.

Tunnel design differs significantly from other structures because of the importance of establishing an accurate geological, geo-mechanical and geotechnical understanding of the area to be tunnelled, including the area excavated and the region around it that is likely to be affected.

It is essential that adequate information is obtained from site investigations to ensure an appropriate level of information for the design (refer to the Guide to Road Tunnels Part 1 (Austroads 2018a), Workplace Health and Safety Queensland (2011): Tunnelling Code of Practice and WorkCover NSW (2006): Tunnels under Construction: Code of Practice). Establishing what is an appropriate level of geotechnical and other information depends upon a range of factors including how quickly a project has to be delivered, the budget for the project, the risk management strategy (which is related to the contractual arrangements in place), other experience and the region involved.

3.1.3. Additional Design Requirements

Experience with tunnel design has shown that the design of the structural elements should consider the following issues:

• The minimum hydraulic head adopted needs to be evaluated as part of the tunnel design whether the tunnel is fully tanked or not.

• Symmetric and asymmetric loads should be considered.

• Analysis of arching may be required, particularly where the cover is less than the width of the tunnel.

• Concrete shrinkage, creep and temperature effects.



• The long-term concrete modulus (particularly in deflection assessments).

• Leakage of water into the tunnel – no water should leak or drip on the tunnel road surface (e.g. the top of the tunnel lining may require a drainage layer and waterproof membrane depending on the specific conditions of the tunnel concerned).

3.2. The Support Function

The information obtained from the site investigation and the anticipated excavation methods should be considered in preparing a tunnel design.

The design should include:

• details on the tunnel dimensions and allowable excavation tolerances

• the initial and/or temporary support and lining requirements for each location within the tunnel

• the permanent support and lining requirements for each location within the tunnel

• any other requirements for the finished tunnel.

It should also include information on the excavation methods and ground conditions considered in the design in order to allow the design to be reviewed if another excavation method is chosen or the actual ground conditions change as the excavation proceeds (refer also to Section 2.4.3).

Most tunnels and open excavations require some form of permanent ground support, which should be designed using the geotechnical information obtained for the project and validated during construction using appropriate testing. Support mechanisms (e.g. rock bolts) must be in ground under the control of the tunnel owning authority (i.e. it is necessary to ensure that adequate land is available to accommodate the ground support).

Removal of material causes unbalanced soil or rock stresses that reduce the capacity of the excavation to support itself.

The designer should undertake a detailed analysis of existing geophysical factors in conjunction with the design requirements (e.g. tunnel dimensions need to be considered), to identify the most appropriate ground support that may be installed without requiring workers to work under unsupported ground.

Ground support systems require consideration of both structural design and soil/rock mechanics. Varying geological conditions mean that different control measures may be needed during the various construction phases.

Design specifications for engineering controls, such as shoring support structures, should be prepared by a competent person in accordance with relevant legislative requirements, Australian Standards, and codes of practice.

Reference should be made to Workplace Health and Safety Queensland (2011): Tunnelling Code of Practice and WorkCover NSW (2006): Tunnels under Construction: Code of Practice.



3.3. Design for Fire and Fire Resistance

Provision for fire safety should be in accordance with the AS 4825: 2011 Tunnel Fire Safety (refer to Section 8).

Structurally, tunnels should, in the event of a fire provide:

• the ability to retain the structural integrity of the tunnel, albeit with some damage, in the event of a major fire

• a limit to structural damage in the direct area of the fire to limit the impact on assets, including adjacent infrastructure and surrounding road networks

• retention of the structural stability as the area cools to ensure safety of personnel entering the site after the fire

• an area near to the fire, but which may still be affected by hot smoke and radiant heat, which provides a level of safety and access for emergency service personnel during an incident

• an area away from the fire, but which may still be affected by hot smoke where emergency equipment continues to operate and where objects do not fall thereby making conditions safe for people trying to escape or for emergency service response efforts accessing the incident

• fire-rated separation between the fire zone and the nearby areas of relative safety, such as a cross passage or the adjacent tunnel.

Typically the rock/soil/concrete pillar largely creates the separation between tunnels. However fire doors in the cross passages and the walls built to house the doors will need to be designed to withstand the required fire resistance. There are some situations, however, where more onerous design conditions are warranted, such as where there is the risk of tunnel collapse or inundation. These include situations:

• where any driven tunnel ramps cross over the main tunnels

• where the driven tunnels are shallow and significant structures above may be affected

• in cut-and-cover tunnels where significant structures above the tunnel may be affected

• intermediate floor/roof levels in multilevel cut-and-cover sections

• where failure of the lining would allow the inrush of water in significant quantities which could not be practically controlled by pumping.

In these situations a secondary lining using a suitable passive fire protection material may be required. Further geological investigations are required to determine the passive resistance provided by rock and soil materials, particularly in areas of poor sub-surface materials. Fire tests may also be required to determine the spalling effect and depth of spalling with the materials used.

3.4. Live Load Capacity

3.4.1. General

Structural components of tunnels carrying traffic loads should be designed for the standard loading according to AS 5100: Set-2007 Bridge Design or the Bridge Manual (3rd edition) (NZ Transport Agency 2013a).

Tunnels (including the roof) should be designed for existing and known future loads (e.g. surface traffic loads, buildings and earth pressures). Easements should be created above, below and around tunnels to ensure that unintended loads are not imposed on the tunnel.

Development guidelines should be derived for each tunnel to reflect the particular circumstances of that tunnel and should include a requirement for any future development in the vicinity of the tunnel to be agreed by the tunnel authority managing it.



3.4.2. Permissible Development and Live Loading above the Tunnel and within the Easement Area

Vehicle live loads – to be applied anywhere in the road corridor

Live loading should be limited to M1600 moving traffic load, S1600 stationary traffic load, A160 axle load and heavy load platform design load in accordance with the requirements of Australian Standard AS 5100.2: 2004 and AS 5100.7: 2004, or the HN-HO-72 loading to NZ Transport Agency (2013a) noting that a dynamic impact factor of 1.3 will be adopted in New Zealand.

In addition, crane outrigger loads should be limited to not exceed the additional loads listed below.

Other additional loads

These may include:

• resulting uniformly distributed working loads acting at the surface of up to 50 kPa

• natural surface level build-up of up to one metre with fill equivalent to a uniformly distributed load of 20 kPa

• any loads from permitted developments above the tunnel (such as residential, commercial or industrial)

• loading due to seismic shaking.

3.4.3. Permissible Excavation within the Easement Area

Where future developments or other activities require the excavation of material from areas adjacent to, above and below the tunnel, they should be assessed by analysis for the tunnel concerned. For any tunnel, a three-dimensional zone around the tunnel where no work can be undertaken without approval should be defined. Approval should only be granted where it can be demonstrated that the effect of the work on the tunnel and the effect of the tunnel on the work is acceptable.

3.4.4. Vehicle-induced Wind-suction

Additional operational loading can occur on internal walls, claddings, false ceilings and the like due to the wind pressures and ‘suctions’ caused by the moving vehicle traffic. Guidance on determining the design factors for this loading is provided in Highways Agency (1999): Design Manual for Roads and Bridges (specifically Clause 2.81).

3.5. Potential Surface Settlement due to Tunnelling

Surface settlement in the general area above tunnels may occur by a variety of mechanisms (singly or in combination) including:

• ground relaxation

• settlement

• construction disturbance and vibrations.

Where significant elastic settlement is predicted to occur in sensitive areas (for example in the portal areas where the tunnel is shallow) mitigation measures will be required in the tunnel design and construction methods to control or reduce the ground movements. This may be achieved by increasing the support to the tunnel roof and/or enhancing the properties of the surrounding ground. In this way settlement may be controlled so that damage to adjacent building structures or services is unlikely.



Settlement may occur because of changes in the ground watertable (Section 7.3) and may not be limited to the area directly above the tunnel. Consideration of the potential wider effects of changes in the ground water level is necessary to ensure that damage to property is minimised and appropriate mitigation strategies are put in place.

In sections of cut-and-cover tunnel in soft ground conditions, settlement adjacent to the structure may occur. Control over this type of settlement could be achieved by limiting the deflection of the embedded wall (contiguous pile wall or diaphragm wall) by propping, tie backs or similar measures.

3.6. Tunnel Seismic Design

The design earthquake acceleration should be based on AS 1170.4: 2007: Structural Design Actions – Earthquake Actions in Australia or NZS 1170.5: 2004: Structural Design Actions – Earthquake Actions in New Zealand as appropriate.

Note that seismic design in New Zealand in particular is under significant review after the Canterbury earthquakes. Therefore more recent guidance should also be considered, including updates to the AS/NZS 1170 standards and notifications from the Ministry of Business, Innovation and Employment regarding compliance with the NZ Building Code.

The design of the completed tunnels for seismic loading should be based on deformation/ displacement compatibility with the surrounding rock mass or soil undergoing cyclic displacement under the design earthquake event.

The acceptance criteria for the design of tunnel structures to resist seismic loads in New Zealand is based on the design philosophy outlined in Section 5 of the Bridge Manual (3rd edition) (NZ Transport Agency 2013a) which is summarised below.

The primary objective of seismic design should be to ensure that the tunnel can safely perform its function of maintaining network access/functionality after a seismic event. The extent to which this is possible will depend on the severity of the event, and thus by implication on its return period.

For design purposes, tunnels should be categorised according to their importance, and assigned a risk or return period factor. This will then result in an equivalent design earthquake hazard and consequent loading.

The performance of the tunnel structure should be assessed against the following criteria:

• After the design return period event (sometimes referred to in other countries as the maximum design earthquake or MDE), the tunnel should be usable by emergency traffic, although damage may have occurred, and some temporary repairs may be required. Permanent repair to reinstate the design capacities for both static and seismic loading should be feasible.

• After an event with a return period significantly less than the design value (sometimes referred to in other countries as the operating design earthquake or ODE), damage should be minor, and there should be no disruption to traffic.

• After an event with a return period significantly greater than the design return period event (the maximum considered earthquake), the tunnel should not collapse, although damage may be extensive. It should be usable by emergency traffic after temporary repairs and should be capable of permanent repair, although a reduced capacity for further seismic events may be acceptable given this is a highly infrequent event.

The design of any tunnel, located in an area which is susceptible to earthquake-induced liquefaction or where the effects of active faults could have an impact on the tunnel, should recognise the large movements which may result from settlements, flotation and movements. Where feasible from a practical, economic and social consequences perspective, measures should be incorporated to mitigate these effects.



4. Geometric Design

4.1. General

In general, geometric design standards defined in the Guide to Road Design Part 3: Geometric Design (Austroads 2016) should be adopted. Variations from the Guide for road tunnels may occur because of the characteristics of tunnels.

The geometry of the tunnel must also be related to the other aspects of tunnel design and operation. This may affect tunnel geometry or require additional space beyond that needed to enclose specified carriageway widths and traffic clearances. For example, the geometry may be influenced by the requirements for:

• ventilation (length and gradients)

• traffic movements (maintenance, emergencies)

• portals (provision for parking/turning emergency vehicles)

• operational safety (verge widths, lay-bys and long tunnels)

• transitions from the external roadway to the tunnel environment and from the tunnel environment to the external roadway

• prevention of over-height vehicles entering the tunnel (adequate sight distance)

• traffic escort (marshalling facilities in portal areas)

• adjacent road network (disruption or queues due to tunnel closures).

The final design will be the result of consideration of all of the factors in combination, taking account of their interaction.

4.2. Sight Distance in Tunnels

Sight distance requirements in tunnels are the same as those for any other part of the road system and these are described in the Guide to Road Design Part 3: Geometric Design (Austroads 2016). In addition, the available sight distance on the approach to the tunnel portal should be sufficient for the approaching driver to be able to come to a stop and still have space available to turn around or be removed, e.g. over-height vehicles that have not been diverted previously. Adequate space has to be provided for this to occur.

Particular attention to the effects of horizontal and vertical curvature is required, where the walls, barriers and equipment suspended from the roof and/or walls may restrict the available sight distance. The most effective way of overcoming this problem is to adopt sufficiently large radii for the curves so that the line of sight is not interfered with by these obstructions (Section 4.4 and Section 4.5.2).

In tunnels where the curvature cannot be improved, the posted speed limit in the tunnel will have to be reduced to provide an adequate level of safety.

Appendix A includes tables of minimum radii to achieve appropriate sight distances based on the following parameters:

Perception/reaction time: 1.5 sec. up to 90 km/h and 2.0 sec. above 90 km/h

Car coefficient of deceleration: 0.46 g

Truck coefficient of deceleration: 0.29 g.

The coefficient of deceleration of 0.46 may be applied as a maximum along the length of a tunnel, with the exception of the 200 m length from the portal entries, where the coefficient of deceleration used is 0.36.



4.3. Operating Speed

In the absence of active enforcement, the 85th percentile operating speed for cars may be assumed to be 10 km/h more than the posted speed. Truck speeds may be less in places due to the size of horizontal curves on ramps or due to the effect of grades (Austroads 2016). The operating speed in the tunnel is to be adopted as the design speed of the various elements of the design.

For safety reasons, the posted speed in two-way tunnels throughout the world is generally between 60 and 80 km/h.

In one-way tunnels, the posted speed may be between 80 and 100 km/h provided conditions will allow adequate safety of operation. Where grades create significant speed differentials between vehicles, the posted speed should be limited to a maximum of 80 km/h. Clearances at the ‘desirable’ end of the range should be provided in high-speed tunnels.

In urban road tunnels with high or potentially high traffic volumes, the posted speed is generally limited to 80 km/h. The design speed would then be 90 km/h in accordance with normal practice as described above.

Factors to consider in determining both the design and posted speed for a tunnel include the:

• design and posted speed consistency on adjacent road segments

• speed environment on the approaches, and for on and off-ramps

• enforcement of speed limits

• number of lanes provided and tunnel cross-section

• effects of any bifurcations and junctions

• geometric limitations in the tunnel

• tolerable speed reduction between successive geometric elements

• consistency in the design and posted speeds between adjacent tunnels in a network of tunnels.

The latter requires consideration of the tunnel not in isolation but potentially as that in a network of tunnels.

For tunnels with a significant number of trucks, additional factors include:

• grades

• clearances to walls

• potential speed differential between trucks and other traffic.

4.4. Horizontal Alignment

The horizontal alignment in tunnels is to be designed in accordance with the requirements of Guide to Road Design Part 3: Geometric Design (Austroads 2016). Specific variations to what is allowed in that Guide include the following:

• Except for curves on ramps where the operating speed is controlled by the horizontal curve, the maximum side friction factor to be adopted is 0.2 (for speeds up to 90 km/h) to account for possible oil spills and of oil build-up through normal use. For design speeds greater than 90 km/h, the absolute maximum side friction factors allowed are less than this figure.

• The minimum crossfall to be used is 2.0%.

• The maximum superelevation to be used for curves in a tunnel is 2.0%. For curves on entry and exit ramps, superelevation may be increased to 4%.



• The crossfalls on the surface roads approaching the portals should be limited to –3.0% since the probability of an incident increases near tunnel entrances because the geometry and environment is in transition, which can lead to incorrect road user behaviour (OECD 1999; United Nations Economic Commission for Europe 2001).

Horizontal sight distance may be a controlling factor on the acceptable radius of horizontal curves (Section 4.2). It may be possible for the markings on the pavement to be arranged to reduce the shoulder width on one side to provide an additional offset to accommodate the line of sight around a horizontal curve. Such an adjustment could allow a smaller radius curve to be acceptable where restrictions prevent an increase in radius.

Since the horizontal clearance in tunnels will be restricted, the radii required to provide stopping sight distance will be the minimum allowable. This should be determined on the basis of truck stopping distance since there is no advantage gained by trucks because of their higher eye height. Such radii may not require superelevation and this is an advantage in tunnels.

It is important to check the stopping sight distance on every horizontal curve as it depends on the length of the curve as well as the tunnel cross-section.

Where possible, curve radii should be sufficiently large to avoid the need for superelevation (refer to Austroads 2016 for appropriate values of side friction to be adopted in conjunction with the adverse cross slope of 2%). Providing superelevation may have an adverse effect on the cross-section and on the provision of service ducts under the road. Drainage requirements may also be affected.

The horizontal and vertical alignments should be coordinated in accordance with the principles described in Guide to Road Design Part 3: Geometric Design (Austroads 2016).

4.5. Vertical Alignment

4.5.1. General

The vertical alignment in tunnels is to be in accordance with Guide to Road Design Part 3: Geometric Design (Austroads 2016).

Because it can be expected that drivers are in a heightened state of alertness in tunnels, the perception reaction times as specified in Section 4.2 may be adopted for the purposes of calculating sight distances.

4.5.2. Vertical Curves

Normal stopping sight distance requirements will apply for all vertical curves, crests and sags. Since tunnels will be artificially lit, the sight distance criteria normally applied to sag vertical curves will not apply. Desirable comfort criteria will apply provided drainage and sight distance requirements can be accommodated.

Sag vertical curves must be designed so that overhead obstructions (e.g. lighting, signs, opacity meters, ventilation fans) will not interfere with the line of sight. In analysing the requirements for sag curves and the impact of the roof height available (including the effect of equipment suspended from the roof), the eye height to be adopted is 2.4 m (truck driver eye height) with an object height of 0.8 m (car tail light).

4.5.3. Grades

In addition to the requirements of Guide to Road Design Part 3: Geometric Design (Austroads 2016), designers must take account of a range of factors that apply to road tunnels (refer also Guide to Road Tunnels Part 1: Introduction to Road Tunnels (Austroads 2018a)).



Designers should take account of the following:

• The effect on driver perceptions caused by the combination of grades and tunnel wall joints. Joints are perpendicular to the grade, rather than vertical, and can distort the perception of distance. Misjudgements on grades between 3% and 5% have been caused by this effect and have led to incidents (Transport and Road Research Laboratory 1987).

• Oil build-up on gradients over 4% has caused heavily-laden articulated vehicles to lose traction.

• Grades should be designed to maintain reasonable truck speed and limit the differential speed of trucks within the traffic stream. This may be the controlling factor.

Factors to be considered in determining the grade include:

• surface tie-in point elevations

• surface alignment obstructions

• sub-surface alignment obstructions

• geology

• traffic composition (% heavy vehicles) and speed differentials created

• tunnel length

• portal flood immunity requirements

• the minimum longitudinal grade required for adequate longitudinal drainage of 0.5%.

Surface development and other constraints will often require steeper than normal grades at surface connections particularly in urban areas and brownfield sites where existing topography can be very constrained. Steeper grades reduce lane capacity, but as the speed environment is lower such grades may be acceptable where their length is short, the traffic demand is relatively low, or the proportion of heavy vehicles is also low. The alignment can be tested with vehicle simulation software (e.g. VEHSIM) to establish an appropriate design.

4.6. Cross-section

4.6.1. General

Cross-section elements are to be designed in accordance with Guide to Road Design Part 3: Geometric Design (Austroads 2016). Because of the tunnel environment, additional factors have to be considered. The cavern needed at ramp junctions may limit the number of lanes that are possible and may control the depth (and hence grades) of the tunnel.

4.6.2. Lane Widths

The standard lane width is 3.5 m and should generally be adopted. These widths provide the capacity and level of service expected of traffic lanes with appropriate clearance on each side.

The capacity of a 3.5 m lane is not reduced if the lateral clearance to a fixed object is 1.8 m. When the clearance is less than this, and/or the lane width is less than 3.5 m, then the capacity will reduce (Austroads 2019a). This clearance is determined by the shoulder widths in tunnels.

Curve widening may be required if the radius of the curve is sufficiently small for the design vehicle selected (Austroads 2015a). However, if the curves are sufficiently large to overcome horizontal sight distance problems, then curve widening should not be an issue.



If the width of traffic lanes in a tunnel is less than that of the adjoining carriageways in the open air sections of roadway and a restricted design speed is applied, the speed limit should commence at least 150 m before the entrance to the tunnel (Amundsen & Sovik 1995; Norwegian Public Roads Administration 1997).

4.6.3. Shoulder Widths

Main tunnel

Shoulders are considered part of the hard clearance zone in conjunction with any identified need for emergency walkways, safety barriers, and emergency stopping bays/pull-off areas. The required functional areas/clearances must be established for the tunnel and kept continuous throughout the tunnel.

PIARC recommends that the hard clearance area be ≤ 1.0 m or ≥ 2.0 m in general traffic tunnels. Dimensions between 1.0 m and 2.0 m lead to operational problems because of potential confusion created for drivers and potential misuse of the available road space by drivers attempting to create an additional lane. However, in two-lane two-way busway tunnels, a 1.4 m minimum shoulder is typically used so that there is some space to allow a broken-down bus to pull over and potentially allow passengers to exit. Tunnel management procedures may then allow other buses to pass the stopped bus.

The wider the hard clearance area, the greater will be the cost of the tunnel. A balance must be sought between the operational needs (e.g. flexibility to close lanes, ability of vehicles to stop clear of the traffic lanes, provision of emergency response facilities) and the costs incurred in providing for them.

If the shoulder is not continuous or is narrow, parking bays or pull-off bays may be considered at intervals. However, such bays may be ineffective as there are indications that in many cases vehicles do not actually reach the facility on breakdown (Norwegian Public Roads Administration 1997).

Stationary traffic resulting from a vehicle breakdown will cause an increased demand on the ventilation system as well as stress to drivers. It is therefore important that for a particular tunnel, consideration be given to a range of physical and operational responses in the context of the tunnel design environment before settling on a particular solution.

Shoulders may have to be widened to provide sight distance on horizontal curves or at ramp junctions. This may require a change in the tunnelling methods adopted.

Ramp and conflict zones

These areas require alternative treatments to the mainline tunnel due to the changed environment, types of hazards likely to be encountered, and types of manoeuvres being undertaken with a general response being an increase in the left-hand shoulder width to enable the passing of a stopped vehicle.

Reference should be made to the Guide to Road Design Part 4C: Interchanges (Austroads 2015a).

4.6.4. Crossfalls

Crossfalls in the tunnel should preferably be 2% to provide drainage of the road surface. This will require radii sufficiently large to allow adverse superelevation (Section 4.4).

The transition between the crossfalls of the tunnel and approach roadways must be incorporated prior to the portal of the tunnel at a rate of rotation of 0.025 radians per second.



4.6.5. Auxiliary Lanes

Auxiliary lanes (e.g. acceleration and deceleration lanes, climbing lanes) may need to be incorporated into the cross-section if the need has been identified in the planning stages of the project. Details of auxiliary lane design are provided in Guide to Road Design Part 3: Geometric Design (Austroads 2016). Limiting the speed differential of vehicles is particularly important in tunnels and if possible, locating speed change facilities away from the tunnel structure is desirable. However, these lanes will provide the appropriate means for safe entry to and exit from through-lanes where this is required.

Additional information on climbing lanes is also included in Guide to Road Design Part 3: Geometric Design (Austroads 2016). Further, a simulation (e.g. VEHSIM) analysis may be used to fully analyse the particular situation and establish whether an auxiliary lane for trucks should be added.

However, additional lanes in a tunnel will be more expensive and may not be able to be included if the span (i.e. cross-sectional width) becomes too large. Where possible, the geometry should be designed to avoid the need for auxiliary lanes. Other means of accommodating the issue may be more cost-effective (e.g. flatter grades, traffic management systems).

4.6.6. Emergency Stopping Lanes

The high additional cost of continuous emergency stopping lanes usually precludes their inclusion in the cross-section. However, additional lane width or widened shoulders can provide a temporary expedient solution for passing stalled vehicles.

4.6.7. Vehicle Refuges for Tunnel Incidents

A vehicle refuge or stopping bay provides space for a vehicle to stop clear of the traffic lane, thereby preventing the traffic stream from becoming unduly congested. The initial cost of providing additional traffic space in the tunnel cross-section to cope with incidents and breakdowns must be balanced against the operational needs of communications, surveillance, stand-by recovery facilities, consequence of traffic delays and pressure on the surrounding road network. Such factors will depend on the length of tunnel, its location (e.g. rural, mountain, urban, sub-aqueous) and on traffic demand.

It may also be difficult and expensive to provide such refuges in some geotechnical conditions and where continuity of the tunnel geometry is very desirable (e.g. submersed tube tunnels, tunnels created with tunnel boring machines).

Advice from those experienced in the management of risks in road tunnels, as well as accident statistics, should be sought to define the need for any additional traffic standing space.

4.6.8. Provision for Evacuation

Unobstructed pedestrian access from the tunnel space to places of relative safety is required. A width of at least 0.6 m level with the pavement is desirable and may be on the left or right side of the pavement depending on the location of the evacuation passageways (for access to cross-passages to the other tunnel bore, the access would usually be on the right-hand side). Note that the road surface itself will be the predominant emergency egress pathway used.

The emergency access should be at the same level as the roadway surface and accessible to people with mobility impairment. It may also be provided in a separate, enclosed combined services/escape void or passage. In addition to serving as access for an emergency exit, it can also be used by maintenance and traffic operations personnel.

If the evacuation access width is raised above the road pavement creating a walkway, a mountable kerb is required to allow wheelchair access to the walkway. Such a space will also be available for vehicles to pull over if required in other circumstances.



The widths available for emergency evacuation in bored tunnels will necessarily be restricted by the cost of the tunnel construction and the normal verge widths will be used for this purpose. In shorter tunnels, wider access ways may be feasible within the constraints of cost. A benefit-cost analysis may provide guidance on the treatment that should be provided.

4.6.9. Emergency Equipment Cabinets

The cross-section should be designed to accommodate emergency equipment cabinets at intervals along the tunnel. The spacing of these cabinets is determined by the requirements for spacing of emergency telephones and fire hose reels and hydrants.

4.6.10. Escape Routes

Escape routes through fire doors positioned in central walls or cross-connecting passages should be provided (Figure 4.1) in accordance with AS 4825: 2011.

Where two or more tunnels are linked by cross-connections, the effect of opening one or more of those cross-connection doors should be considered in both normal and emergency situations. The design should incorporate features which reduce or eliminate any hazard likely to be caused by any opening of a cross-connection. There may also be a need for protection at the cross-doors in the hard clearance area against the other tube traffic if there is an unacceptable risk that such traffic may not have cleared the tunnel tube or may not have been stopped when people use the escape route.

Cross-passages are also used for the accommodation of equipment for communications and systems control. Deluge manifolds and adequate space and protection are required for them, in addition to a passageway suitable for the movement of people during evacuation, or for maintenance and inspection personnel. Note that while the communications and electrical equipment can be located within a cross-passage, it must be in its own separate fire-rated space.

Figure 4.1: Identifying the escape route (CityLink tunnel, Melbourne)

Source: Transurban.



4.6.11. Traffic Barriers

The design of traffic barriers is to be in accordance with the Guide to Road Design Part 6: Roadside Design, Safety and Barriers (Austroads 2010). However, the characteristics of tunnels may need further consideration of the details of the design of the barriers, and this is discussed in this section.

The geometric shape of a tunnel poses additional risks that are required to be protected by barriers. These include:

• protecting the tunnel and other infrastructure from being impacted by vehicles

• reduced sight distances on curved sections

• reduced lateral clearances.

Traffic barriers in tunnels should be concrete with a profile that is acceptable to the road agency. Some road agencies now normally use single-slope concrete barriers with a minimum height of 1100 mm. However, an 800 mm high barrier may be considered if this helps achieve sight distance and the operating speed for both cars and trucks is ≤ 90 km/h, and allowance for working width is made as described in Section 4.6.12.

The effect of the barriers on the movement of pedestrians during an emergency must also be considered, as appropriate access to places of relative safety must be provided.

Special consideration should be given to the provision of crash cushions at tunnel entrances, approaches to tunnels, and merge and diverge areas. The confined space of the tunnel must be adequately considered when designing for crash cushions.

4.6.12. Working Width

Working width is described in Guide to Road Design Part 6: Roadside Design, Safety and Barriers (Austroads 2010).

If the likelihood of a vehicle travelling close to the barrier is low, it may be possible to reduce the working width. These conditions may be achieved when:

• impact frequency is considered low (low % heavy vehicles)

• shoulder widths are sufficient to reduce impact potential

• increased lateral widths are required to attain sight visibility to reduce impact potential.

In addition, consideration can be given to the following factors:

• potential damage caused during a crash will be generally localised

• repairs to walls or cladding can be undertaken during off-peak lane closures

• maintenance requirements are not expected to be onerous.

However, the potential damage to vehicles that may impact the wall or attachments to the walls must be taken into account.

The working width in the tunnel proper may not be required if:

• there is no obstacle that will snag part of a heavy vehicle that impacts the barrier

• there is a suitable transition from the area where barriers must have the working width (this is usually achieved by sloping the top of the wall on the tunnel transition).

Note also that some tunnels have an architectural panel that will be incapable of withstanding an impact on top of the barrier. Any other equipment within the working width must be frangible.



4.6.13. Tunnel Envelope and Vehicle Clearance

Vertical clearance

In addition to network constraints there are a number of other factors affecting the selection of tunnel height clearances including:

• network consistency

• the likely number of vehicles over the maximum permissible vehicle height given the freight route designation

• the availability of alternative routes that accommodate the higher vehicles

• the desirability of the higher vehicles using alternative routes

• the limited benefits of allowing the higher vehicles on the route (e.g. any forgone toll revenues, time savings, urban amenity)

• the likely cost of including additional clearance allowances over the full length of the tunnel project. (The direct cost of damage to a section of the tunnel lighting, ventilation, signage, structural elements, etc. of an errant over-height vehicle entering the tunnel plus the disruption costs should be included in any benefit-cost analysis.)

Note that tunnels will not usually be part of the high clearance network for the road system. A benefit-cost analysis is required to justify additional height clearances if high loads are to be accommodated in a tunnel. Alternative routes should be assessed before adopting higher clearances in the tunnel.

Appropriate allowances for the equipment required for overhead signage, lighting, fire protection jet fans and any smoke ducting requirements must be included in determining the overall dimensions of the tunnel. Mitigating measures may include placing the jet fans in recesses in the soffit or locating the fans in any corners. This equipment must fit entirely within the envelope and the required clearances for protection from compressible loads that pass under the tunnel portal, loose ropes, flapping tarpaulins and the like.

The type of construction (e.g. cut-and-cover, driven or bored) may influence a decision as the resulting cross-sections are different. Bored tunnels are circular, driven tunnels have a somewhat flatter roof and cut-and-cover tunnel roofs are generally flat.

Clearances should be carefully related to carriageway and side verge widths and to the minimum ‘as-built’ structural profile that the tunnel must achieve. Note also that dimensional tolerances of bored, cut-and-cover and immersed tube tunnels are strongly influenced by the construction process.

Over-height vehicle protection

To protect tunnel equipment from damage from over-height vehicles and potential secondary incidents, appropriate advisory signage should be incorporated within the tunnel portal and prior to the last opportunity for a vehicle to take an alternative route (Section 12.3.9). A protection barrier is required immediately prior to the tunnel portal to prevent the entry of vehicles that have ignored the warning messages. A virtual barrier using hologram technology could be considered (e.g. Sydney Harbour Tunnel).

Installation of traffic signals and red light cameras should also be considered.



Portal barriers should:

• be located on the approach side of emergency median crossings near the tunnel portal so that traffic access to these emergency median crossings is also controlled

• be located at a sufficient distance from the portals to allow a suitable staging area for emergency services during incidents

• provide a physical barrier across all traffic lanes and shoulders

• allow the passage of emergency and maintenance vehicles

• prevent damage to signage over tunnel portals and entrance through strutting or architectural furniture prior to the portal.

These barriers are often made of steel rail and frame construction and should comply with the load resistance requirements of AS 5100 Set-2007 or NZ Transport Agency (2013a). The design should ensure that the damage resulting from an over-height vehicle impacting the barrier will not create an undue risk to other road users.

For flat-roofed portals a steel insert may be placed on the leading edge, incorporated into a small reduction in the height of the portal soffit (in the order of 50 mm).

4.7. Ramp Connections/Diverges and Merges

In general, locating ramp connections, diverges and merges within the tunnel or close to the tunnel portals is not desirable and if possible the overall road layout should provide for these movements separate from the tunnel and its portals. However, there will be cases where such connections are required as an essential part of the road network and their design needs to recognise the particular characteristics of tunnels.

Entrances to and exits from the tunnel should be designed in accordance with the Guide to Road Design Part 4C: Interchanges (Austroads 2015a), as modified by Figure 4.2, Figure 4.3, Figure 4.4 and Figure 4.5 of Part 3. Note that entry ramps must enter on the left-hand side of the carriageway.

Divergence of two major carriageways should be designed in accordance with Figure 4.3 and branch connections (convergence of two major carriageways) in accordance with Figure 4.5.

Appropriate crash attenuation devices should be used in gore areas and designed in accordance with Guide to Road Design Part 6: Roadside Design, Safety and Barriers (Austroads 2010) and as shown in Figure 4.2, Figure 4.3, Figure 4.4 and Figure 4.5.

4.8. Emergency and Maintenance Facilities

4.8.1. Vehicle Crossovers

Vehicle crossovers may be required on tunnel approaches to enable contra-flow operation in twin bore tunnels, or convoy operation (i.e. one-way operation alternatively for each direction) in single bore tunnels to meet maintenance and operational needs. If there is an intersection near the tunnel, care should be taken to ensure that all traffic can use the crossovers. Care should also be taken that sight lines are provided through crossovers, particularly those adjacent to widely spaced twin bores, and that suitable temporary or permanent signing, including any necessary speed limit signs is also provided. Crossovers should also be considered for emergency services vehicles to assist access to either tube.

During normal operation, suitable means of preventing vehicles from crossing from one carriageway to the other must be provided to avoid a safety hazard. When implementing contra-flow operation, movable or demountable barriers should be considered and evaluated in terms of possible reductions in maintenance costs.



Where contra-flow operations are to be provided, ventilation and fire safety requirements need additional consideration. In many cases, suitable alternative routes will provide a more cost-effective way of dealing with closure of one of the tunnel bores.

4.8.2. Turning Bays

In long tunnels, consideration should be given to providing for emergency vehicles to turn around, and if this provision is made, the effects on fire separation, ventilation and smoke control must be considered.

4.8.3. Emergency Services Access and Parking

Access for fire brigade and emergency services is essential for appropriate response to fire and other emergencies. A staging area should be provided for the parking of emergency services and police vehicles and equipment. This may require staging areas at each access point. While access via the portals is usual, it may be possible to provide access by way of intermediate ventilation stations or intermediate emergency egress facilities. Such means of emergency access should be considered in the design of the tunnel and appropriate facilities provided.



Figure 4.2: Exit ramps in tunnels



Figure 4.3: Exit ramps – major diverge and secondary exit on a ramp in tunnels



Figure 4.4: Entry ramps in tunnels



Figure 4.5: Branch connections in tunnels



5. Pavement Design

5.1. General

Pavements are categorised as:

• Surface roads – conventional granular with a thin wearing course, flexible and concrete pavements.

• Pavements within tunnels and designed as a conventional pavement.

• Pavements that are structural slabs or floors and designed like a bridge.

• The ramp leading into a tunnel is typically a ‘U” shaped structure where the walls and base are reinforced concrete and the pavement is the structural reinforced concrete floor with an asphalt wearing course.

Underpasses with the sole purpose of moving traffic under a carriageway or lanes, are not considered tunnels.

Details of the pavement types in tunnels are discussed in Section 5.2. Refer to Commentary 1 in Guide to Road Tunnels Part 1: Introduction to Road Tunnels (Austroads 2018a) for more details of the types of tunnel construction and structures.

The following sections follow a similar sequence as the Guide to Pavement Technology Part 2: Pavement Structural Design (Austroads 2017a).

5.2. Tunnel Structure and Pavement

Unlike traditional flexible and rigid pavements where selection of the pavement is typically chosen on the lowest whole of life costs, the pavement structure for a tunnel is dependent on the tunnel type. Section 3.3 of Guide to Road Tunnels Part 1 (Austroads 2018a) notes that tunnels are constructed in a wide range of geological and geographical conditions and environments, which will impact on the selection of the following construction approaches:

• cut-and-cover where the tunnel ceiling is at a shallow depth below the existing ground level

• cast-in-place structure in a waterway using a coffer dam

• immersed reinforced precast concrete tube sunk into place for underwater crossings

• mined or bored tunnels where there is sufficient ground cover

• combinations of the above.

In Sydney, where there is sound sandstone rock, many of the road tunnels are mined and the walls and ceiling of the tunnel are shotcreted, as shown in Figure 5.1. In these tunnels, the tunnel is ‘drained’ or free to leak behind the walls and under the floor, and the pavement is constructed directly onto the floor of the tunnel with the first pavement layer being a drainage layer. If water infiltration levels into the tunnel are high, the tunnel is tanked and lined with cast-in-place or precast concrete walls (shown in Figure 5.2).

The shape of a tanked tunnel is either circular or elliptical for two or thee lanes in width respectively. As shown in Figure 5.3, a circular tunnel section requires significant backfill material compared to an elliptical tunnel section where the backfill is less than 1.0 m in depth. In these cases, the tunnel is supported on backfill earthworks constructed to road agency earthworks specifications and designed in accordance with a conventional pavement design procedure with the design subgrade strength limited to 15%.



Figure 5.1: Typical cross-section of a drained mined tunnel and the pavement is placed onto the floor of the tunnel

Figure 5.2: A mined tunnel under construction with the walls and ceiling being tanked before concrete is placed

Source: George Vorobieff.

Fall

Shoulder ShoulderTraffic lane Traffic lane

Pavement layers

Shotcrete walls and ceilings

Specific drainage pit for tunnels

‘Dental’ concrete in dipsFloor of mined tunnel



Figure 5.3: A circular (left) and elliptical (right) tunnel cross-section with common backfill profiles

Source: The Highways Agency (1999).

For underwater crossing tunnels constructed by precast concrete in the form of an immersed tube sunk into place, the pavement is integrated into the structure, such that only the wearing course is required (refer to Figure 5.4. In some cases, the tunnel designer may require additional mass for the tunnel and a cast-in-place mass concrete layer is included in the profile.

Figure 5.4: Cross-section of a no cell and centre cell immersed tube tunnel where the floor of the tunnel becomes the pavement

Source: The Highways Agency (1999).

The pavement structure for a cut-and-cover tunnel will vary according to the function of the floor of the tunnel and the ground water level (refer to Figure 5.5). For example, if the ground water level is above the pavement surface, the uplift pressure results in a thick concrete layer spanning between walls of the tunnel and the pavement becomes the structural floor of the tunnel. Alternatively, the pavement in cut-and-cover tunnel may consist of reinforced concrete with evenly spaced vertical ground anchors drilled into the formation and the pavement is also under compression due to lateral loading from the earth pressure behind the tunnel walls.

Pavement designers must always work closely with road designers, structural and geotechnical engineers, and geologists to ensure the pavement design, including subsurface drainage where required, takes into consideration various ground support conditions along the length of the tunnel, surface drainage details in the tunnel and near the tunnel portals, the tunnel construction method and all operational conditions.



Figure 5.5: Typical section through a cut-and-cover tunnel with a thick reinforced concrete pavement

5.3. Health and Safety in Design

Throughout the design process, designs must include analysis of Health and Safety in Design (HSiD) implications for both construction and all subsequent life cycle phases of the asset (commissioning, operation, inspection and maintenance, modification, decommissioning and demolition). Pavement engineering input may not commence until the start of the detailed design process and appropriate agency guidelines considered at the early design stages will minimise changes to pavement configurations in the final design.

Documentary evidence of the designer’s and project manager’s efforts and due diligence with regard to Health and Safety in Design throughout the design stages is to be retained. The pavement designer is to contribute to the assessment of the hazard and demonstrate that this has been addressed in the safety in design process.

5.4. Pavement Design Period

The common design period of tunnels is 100 years and durable materials are sought for the tunnel structure. However not all structural, electrical and mechanical elements in tunnels are designed for 100 years, and for example, the design period for mechanical and electrical equipment is up to 25 years. The typical design traffic period for heavy duty pavements is 40 years and this period is chosen to determine the estimated number of heavy vehicle repetitions onto the pavement in order to size the base and subbase layers. The pavement may exceed the design period of 40 years however, when built according to surface road specifications before reconstruction with common preservation techniques.

For freeways and motorways, the project reliability is chosen at 95% (refer to Table 2.1, in Guide to Pavement Technology Part 2 (Austroads 2017a). For tunnel pavements, a higher project reliability (ie 97.5%) is warranted as pavement rehabilitation would be costly and cause significant disruption to the road network.

5.5. Design Traffic

The type of vehicles that use tunnels are Austroads Classes 1 to 12. Vehicles carrying dangerous goods are generally not permitted in tunnels (refer to Section 2.2, Guide to Pavement Technology Part 2 (Austroads 2017a) for further information).

Tunnel owners and operators consider that specialised vehicles that exceed the legal axle limits and dimensions are unlikely to use tunnels and would use surface roads. However during construction, it is not uncommon for sections of the pavement to be designed for high axle loads from earthmoving vehicles using the pavement as a haul road.



Determination of the design traffic follows the same procedure as detailed in Section 7, Guide to Pavement Technology Part 2 (Austroads 2017a). Some key considerations for determining the design traffic over a 40-year design period are:

• Use the heavy vehicle daily traffic rather than a percent of the estimated AADT in the first year.

• Estimate the annual growth of heavy vehicles and do not assume it is similar to light vehicles or that the growth will be constant during the design period.

• Use a Traffic Load Distribution based on similar tunnel WIM data or conduct a route analysis.

• Table 7.3, Guide to Pavement Technology Part 2 (Austroads 2017a) notes a Lane Distribution Factor of 1.0 for a two-lane road. It is unlikely that all heavy vehicles will use the left lane of a two-lane tunnel and it is suggested that traffic distribution data be sought from existing local tunnels.

• Determine if the estimated design traffic over 40 years is to be reduced due to the lane capacity being reached within the design period. For more details on calculating the lane capacity, refer to Section 7.4.6, Guide to Pavement Technology Part 2 (Austroads 2017a).

5.6. Pavement Wearing Surface

The pavement wearing surface may be either asphalt or concrete, and this will depend on:

• The design period required and taking into consideration the cost to replace the surface and possibly reinstate joints.

• Aquaplaning potential near the entrance and exit zones of the tunnels and surface geometry and may require specific requirements for minimum surface texture depth of transverse grooves.

• The required skid resistance at construction and intervention triggers during the operation of the tunnel may be lowered due to the dry surface of the tunnel.

• Light or dark pavement surfaces and the reflectivity impact on lighting design (i.e. lighter road surface requires less lighting).

• Construction equipment operational dimensional limits for pavement resurfacing.

• The susceptibility to damage by vehicle oil droppings and spills, and water leaks from the tunnel ceiling.

With the exception of the entry and exit zones near the tunnel portal and the periodic testing of the deluge fire system, the pavement surface is continuously dry. Without the surface becoming wet and moving tyres to assist in flushing the surface, it is likely that any surface texture may become clogged and reduce skid resistance.

No road agencies permit open graded asphalt (OGA) surfaces as they may retain flammable or toxic spillages arising from an incident. However when an OGA layer is used outside the tunnel portal it should be above the level of drain covers to allow the layer to drain into the pit. Although this causes ride discomfort at the change in levels when pits are located in the trafficable lane, holes cut into the pit frame to drain the OGA layer have been unsuccessful.

When using concrete pavements without an asphalt wearing surface, consideration should be given to a longitudinal hessian drag and tining surface finish in the wet concrete or diamond grinding the surface before opening the tunnel for operation. Most agencies require an additional 10 mm in thickness1 in the concrete base to allow for future diamond grinding in the trafficable lanes and feathering the grinding into the shoulder.

1 Typically representing a 5 mm average grinding depth per treatment.



5.7. Construction and Maintenance Considerations

It is common to use road agency road making specifications for pavements in tunnels. Due to the limited operating height in tunnels, the designer should take into consideration the cumulative positive tolerances in specifications of various pavement layers. Although it is impractical to reduce the construction tolerances, the tolerance could be adjusted such that the positive tolerance is set at +0.0 mm and 10 mm is added to the critical pavement layer after the pavement analysis is completed. Specific pavement layer tolerances are to be included in the design brief and related road making specifications.

Where movement joints occur in tunnel structures and pavements, such as for submersible units every 100 m or at the interface between different tunnel types or at portals, the design of these joints must take into consideration future maintenance activities. For example, future diamond grinding or mill and resheeting the asphalt wearing course should be undertaken without damaging or causing distress to the joint system. Another issue is whether the joint can be reinstated in an efficient manner to minimise the tunnel closure period. In some instances where the pavement wearing course is dense graded asphalt, a different asphalt mix may be required in the wide joint slot.

Where asphalt wearing surfaces require milling operations, a safe working environment needs to be considered where there may be dust generation and exhaust fumes from conventional equipment in the closed environment of the tunnel.

If a waterproof membrane is required to protect the concrete structure supporting the asphalt wearing course, consideration must be given to the life of the membrane and whether mill and resheeting operations would have an impact on the long-term durability of the membrane.

White coloured line marking on concrete surfaces of surface roads and in tunnels is common. A technique used to enhance the dashed line marking is to use black strips on either side of the white dash. Alternatively, a raised marker may be used at the start of the dash.

5.8. Tunnel Environment

The climate in a road tunnel is typically constant and relatively dry, except at the entrance of the tunnel where the sun may heat the pavement surface and wind driven rain frequently wets the pavement surface. There is no published data for the ambient air temperature inside a tunnel, however anecdotal evidence indicates that the air temperature is approximately 25°C. Unless other data is provided by the road agency, it is suggested that 25°C be used in lieu of the WAMPT for the site of the tunnel (refer to Appendix B, Guide to Pavement Technology Part 2 (Austroads 2017a) for more information).

In mined tunnels, water leaks are known to occur and wet patches may be visible on the pavement surface (as shown in Figure 5.6).

Figure 5.6: View of a wet patch and staining from a water leak occurring from the ceiling of the tunnel




5.9. Subgrade Evaluation

The subgrade support strength for pavements varies in different tunnel types and moisture movement in undrained tunnels is insignificant compared to the high levels of moisture likely to occur in wet mined tunnels. Soils used for earthwork layers in tunnels should be durable and not breakdown due to repeated dry and wetting, and repeated traffic loading.

The maximum permissible design subgrade strength for pavements in Guide to Pavement Technology Part 2 (Austroads 2017a) is 15%. For the design of a concrete pavement, the maximum effective subgrade strength is 75% for a 150 mm thick lean-mix concrete subbase and design subgrade strength of 5% or greater (refer to Figure 9.1, Guide to Pavement Technology Part 2 (Austroads 2017a)). Given that a minimum 200 thick layer of no fines concrete subbase is generally used in drained tunnels, it is considered that this subbase layer is equivalent to a 150 mm thick lean-mix concrete layer.

For a flexible pavement design supported on the floor of a mined rock tunnel, the maximum design subgrade strength limit of 15% is still to be applied (refer to Section 3.6, Guide to Pavement Technology Part 2 (Austroads 2017a)).

5.10. Surface and Subsurface Drainage

Detailed guidance for pavement subsurface drainage is provided in the Guide to Pavement Technology Part 10: Subsurface Drainage (Austroads 2009c) but has limited applicability to tunnels. Although undrained tunnels may be considered dry, the entrances to tunnels, leaking joints and the testing of the fire water system will result in water entering the pavement and supporting layers. A subsurface drainage system should be designed and incorporated in the lowest point of an undrained tunnel or on the low side of the drained tunnel. A durable filter material for these subsurface drains and layers consists of no fines concrete rather than single-size aggregate or coarse sand commonly used in trench drains for surface roads.

In NSW where the pavement is supported on sound rock in a mined tunnel, the subbase layer in a continuously reinforced concrete pavement is no fines concrete and a trench drain is located on the low side of the pavement. Typically, the trench drain is 300 mm wide and 300 mm deep (below the underside of the subbase). If the supporting rock has a high fines content or likely to break down over time, a geotextile fabric is placed on the floor of the tunnel. If the longitudinal grade exceeds 3%, such as near the entrance or exit to a tunnel, additional transverse trench drains every 50 m are incorporated in the no fines concrete subbase to improve moisture movement into the subsurface drainage system.

In tunnels where the pavement is the structural floor of the tunnel, subsurface drains may not be applicable because the floor and walls may be tanked.

Most agencies do not permit drainage pits to be located in the trafficable lane and a minimum 1.0 m wide shoulder is used to locate the pit and cover (refer to Figure 5.7). When pit covers or other utility access covers are located in the trafficable lane, the covers are subject to tyre impact loads and a bump in the surface occurs resulting in reduced ride quality.



Figure 5.7: All surface drainage pit covers should be located in the shoulder and not in the trafficable lane


5.11. Pavement Materials

Pavement materials used for surface roads are also suitable for pavements in tunnels, however unbound and modified granular materials are unlikely to be used due to the thickness required to meet the long design life. Additional costs for excavation compared to other pavement alternatives are also an issue.

Where asphalt is used, the factors affecting the asphalt fatigue life are similar to those listed in Section 6.5.9, of Guide to Pavement Technology Part 2 (Austroads 2017a), except the operating environment is constant and apart from the tunnel portal zone, the asphalt would not be subject to heating and cooling from solar exposure. Although the posted speed limit in tunnels could be as high as 100 km/h, heavy vehicle speeds are likely to be well below the posted speed limit due to traffic congestion in urban areas. Consideration should be given to the impact on asphalt modulus from steep longitudinal grades at tunnel exits and generally lower traffic speed.

Conventional concrete mixes used for surface concrete roads has been successfully used for concrete pavements in tunnels. Where a drainage layer is required, it is common to use a no fines concrete mix with a compressive strength varying from 5 to 20 MPa (Roads and Maritime Services 2016). There is no information on the assigned design modulus of this material and laboratory testing would have to be undertaken should a no fines concrete mix be used as a subbase in a flexible pavement.

In mined tunnels a ‘road header’ is commonly used to excavate rock and the floor of the tunnel is not always uniform or pockets of weak material are removed. In these instances, and where the tunnel floor and walls are not permanently lined or tanked, a lean-mix concrete (sometimes referred to as ‘dental concrete’) is placed in these small depressions. It is unusual for lean-mix concrete to cover the full width of the tunnel floor.



5.12. Design of Pavement

The design of a flexible or rigid pavement in a tunnel is no different to the design of a surface road. The design method outlined for flexible and rigid pavements in Sections 8 and 9 in Guide to Pavement Technology Part 2 (Austroads 2017a) respectively, is to be used.

Where asphalt is used, the selection of the binder and therefore, the design properties of the asphalt used for the mechanistic-empirical procedure should take into consideration the potential wet environment in a drained tunnel and that there is no sunlight (except at the tunnel portals) on the asphalt to make the binder harden.

For rigid pavements in a drained tunnel, the concrete base layer must not be placed directly on a no-fines concrete subbase and a 30 mm thick asphalt interlayer is commonly used to sperate the base and subbase (refer to Figure 5.8). This interlayer does not preclude the same rigid pavement design procedure detailed in Section 9 of Guide to Pavement Technology Part 2 (Austroads 2017a). With the relatively constant pavement temperature in the tunnel (except at entry ramps), the minimum amount of longitudinal reinforcement is used in continuously reinforced concrete base.

Figure 5.8: Typical pavement profile of CRCP base layer, AC7 asphalt interlayer and no fines concrete subbase for drained tunnel

In some tunnels, the pavement may be the structural floor and no pavement design is required. Design detailing is to be given to the requirement of a wearing surface and expansion joints where specified in the design brief.

CRCP Min. 250 mm

AC7 interlayer Min 30 mm

No fines concrete subbase Min. 200 mm

Design subgrade or floor of tunnel



6. Environmental Considerations

6.1. Noise

6.1.1. Tunnel-generated External Noise

The source of noise emanating from a tunnel is generally that produced by the tunnel ventilation system, namely:

• reverberant noise

• air path noise

• break-out noise

• portal noise.

The control of noise to the outside environment will depend on individual circumstances and the area background noise levels during fan operation. The external noise generated should not exceed acceptable standards for nearby noise-sensitive development.

Portal noise is influenced by a number of factors including engine noise (particularly trucks) and tyre noise from the pavement. It can also be influenced by the location of fans inside the tunnel and the design will have to consider this when deciding on the proximity of fans to the portal.

In addition, long concrete tunnels may have an effect on concentrating and directing sound energy emanating from the tunnel. There may also be differences in the frequency of road surface noise generated by various surface types (e.g. brushed concrete versus asphalt) and appropriate mitigation measures may have to be implemented.

Section 9.4.1 provides guidance on the design of fans to limit the noise generated from the system.

The noise generated by the flow of traffic also has to be considered and appropriate mitigation measures taken to limit the exposure of nearby noise-sensitive receptors. The Guide to Road Design Part 6B: Roadside Environment (Austroads 2015b) provides guidance on controlling noise from this source. In New Zealand, practitioners should refer to NZS 6806: 2010, and State Highway Noise Barrier Design (NZ Transport Agency 2010b).

6.1.2. In-tunnel Noise

In-tunnel noise is produced from the tunnel ventilation and other equipment as well as from the traffic using the tunnel. Section 9.4.1 provides guidance on the acceptable level of in-tunnel noise.



6.1.3. Traffic Noise

The construction of elevated and transition structures to tunnels should incorporate elements designed to minimise the transmission of vehicle noise to any adjacent or nearby habitable buildings.

This may include the provision of:

• noise panels in transition structures

• an open graded asphalt (OGA) surfacing – referred to as open graded porous asphalt (OGPA) in New Zealand – on elevated and transition structures and surface roads (not in the tunnels as the OGA conveys spills of flammable liquids into the pavement making them difficult to collect and liable to fire which will be difficult to extinguish) curved sound-absorbent panels on the sides of portal entrances and elevated transition structures.

Specific noise criteria should be defined on a case by case basis to meet local environmental requirements. Practitioners should therefore refer to local jurisdictional guidelines for the relevant criteria and measures to mitigate the effects of noise associated with vehicles and other tunnel operations.

6.2. Visual Amenity Considerations

6.2.1. General Considerations

Planning for a tunnel should include consideration of the urban design implications of the project ensuring that the principles of urban design are applied (refer to Roads and Maritime Services 2014). This should result in infrastructure that is not only fit for purpose but is integrated well with the surrounding environment, is sensitive to its context and provides a visually acceptable product.

The planning should also consider the potential improvements for existing roads and connections associated with the project, since the implementation of the project will divert traffic from these roads thereby providing an opportunity to improve the local environment. It is also the case that providing a tunnel for an urban road allows the surface land to be retained for higher and better uses.

The visual impact of tunnels is generally limited to the portals and structures associated with the tunnel, but external to the tunnel (e.g. ventilation exhausts) as well as the transition areas between the open road and the tunnel proper. A specialist in the field of landscape and urban design will be required to develop these needs, which should be considered and resolved in the earliest stages of the project planning. Figure 6.1 and Figure 6.2 show examples of the urban design of tunnel portals.

The internal appearance of the tunnel should reassure the drivers as to the safety of the tunnel (Figure 6.3), be well signed both for general navigation requirements and for emergency conditions, and have surfaces conducive to good lighting conditions (Section 10).

6.2.2. Portal Design

The tunnel portal is the transition between the above and below-ground sections of the highway where the road user moves from one driving environment to another. The portal design should be considered from the perspective of the user and of the external observer as both have different expectations.

From the road user perspective, the design of the portal should contribute to road safety and driver behaviour by assisting the road user to negotiate the transition between the open road and the tunnel environment by reassuring the driver that it is safe to proceed into the tunnel.

The external observer requires the visual impact of the tunnel portal to be mitigated and integrated with the surrounding environment. Attention to the architectural detailing and material selection as well as the bulk and massing of these elements will assist in achieving these requirements.



Landscaping of the surrounding space should be undertaken in accordance with the requirements of Guide to Road Design Part 6B: Roadside Environment (Austroads 2015b). Additional guidance may be found in Roads and Maritime Services (2014) and Sheridan (2009).

6.2.3. Transition Zones

The design of transition zones between the tunnel and the open road should:

• give the driver confidence in entering the tunnel environment

• provide a suitable transition from the tunnel to the external environment on leaving the tunnel

• place the tunnel infrastructure in context with reference to the tunnel approaches and the surrounding environment.

Further guidance may be obtained from Roads and Maritime Services (2014) and Sheridan (2009).

Figure 6.1: Portal and transition design – EastLink tunnel, Victoria

Source: Linking Melbourne Authority.



Figure 6.2: Entrance to Heysen tunnels – South Australia

Source: Department of Planning, Transport and Infrastructure, South Australia.

Figure 6.3: Entrance to the Lane Cove tunnel – Sydney

Source: Roads and Maritime Services, NSW (2014).



6.2.4. Internal Tunnel Design

Variations in tunnel space may be considered and will depend on tunnel length, and may consider:

• possibilities for interior variation

• lighting which breaks the monotony

• variations afforded by the line and geometry of the tunnel.

The design of the interior of the tunnel should:

• maintain the driver’s attention to the driving task

• enable the driver to navigate the system safely

• provide clear and unambiguous guidance during emergency situations

• ensure that lighting is appropriate and free from ‘flicker’ (Section 10.3.4)

• provide a pleasing experience.

Providing an experience different from that of the open road is an important part of the design of the tunnel interior. The combination of the alignment, signing, lighting and wall and roof treatments can be used to achieve the design objectives (Figure 6.4).

Bradley (2011) notes the following:

Our studies show that some drivers feel unsettled when driving through a tunnel; for some, the feeling of discomfort is so great that they choose a different route. Studies show that such feelings can be eliminated or reduced by using creative and good lighting, decoration, high maintenance standards, and clear information with frequent signage.

Signs and equipment must be clearly visible and easily accessible and incorporated into the general architecture. This also applies to emergency cabinets, boxes housing technical equipment, fire extinguishers, doors and hatches, etc.

Equipment should be painted in a colour appropriate to the overall design and in keeping with any specific theme being used to coordinate the design, but retain consistency with the rest of the road network for commonly used items (e.g. help phones). Standard colours for safe egress points and directions (green) and fire cabinets (red) should be adopted.

Illumination which faithfully reflects colours should be chosen where practicable. In long tunnels in particular, attention should be given to breaking the monotony by creating variation with the aid of illumination. One solution can be to choose special illumination, for example in niches or emergency lay-bys (Norwegian Public Roads Administration 2004).



Figure 6.4: Typical tunnel interior


6.2.5. External Structures

External structures should generally be in keeping with the surrounding land use and be as unobtrusive as possible while retaining their functionality. It may be possible, however, to contribute to the architectural interest of the area by designing a ‘landmark’ structure as a significant feature of the urban design. Specialist design expertise will be required to create an appropriate structure in keeping with a theme for the project or a local theme.

Structures directly associated with the tunnel operation and in close proximity to the tunnel should be integrated with the tunnel infrastructure as far as possible.

If required, ventilation structures should be designed to ensure that there is adequate dispersion and dilution of emissions from vehicles using the tunnel. Where possible they should be located as close to the tunnel portal as possible so that their function is easily understood and they ‘announce’ the entrance to the tunnel.

Ventilation structures may be significant structures in their own right and may be designed carefully to fit in with their surroundings or may be designed as a landmark structure (Figure 6.5 and Figure 6.6). Ventilation stacks can be an important part of the urban design that adds visual interest, reinforces a sense of place, and ties in to the design of the tunnel approaches. The size of these structures often requires such specialised treatment. Using existing structures to incorporate the ventilation requirements is sometimes possible, in which case, the presence of the ventilation structure is generally hidden.



Figure 6.5: Cross-city tunnel ventilation Sydney


Figure 6.6: Lane Cove tunnel ventilation Sydney




6.3. Air Quality

6.3.1. Internal Tunnel Requirements

The quality of the air inside the tunnel has to be suitable for its proposed use. Different exposure limits may apply for users and for maintenance workers in different jurisdictions. Pollutants to be considered are nitrogen dioxide, carbon monoxide and particulates arising from engine exhausts, tyre wear and dust. In addition, sulphur dioxide and hydrocarbons which are more relevant when long duration tunnel exposures can occur.

Exposure to in-tunnel levels of sulphur dioxide and hydrocarbons represent a lower risk to tunnel users relative to the other air contaminants given the small proportion of emissions that these represent relative to total vehicle emissions and, in the case of hydrocarbons, the period that users are exposed to such pollutants. It can be safely assumed that adequate dilution of these emissions will be provided for by the ventilation system (see Section 9 for details of ventilation design). However, these two pollutants are critically important in designing for durability. Carbon dioxide is especially important and has been a potential design driver for concrete cover over the reinforcement.

6.3.2. External Air Quality Requirements

For Australia, the National Environment Protection Council of Australia (NEPC) has determined a set of air quality goals, which are part of the National Environment Protection Measures (NEPM). NEPM air quality limits are specifically nominated as not applying to road or tunnel projects and are intended to apply as a background limit. It is important to note that the standards established as part of the NEPM are designed to provide an ‘average’ representation of general air quality and are not designed to be applied to monitoring peak concentrations from major emission sources.

For further information relating to Australia, designers and practitioners should refer to the National Environment Protection Council (2011): National Environment Protection (Ambient Air Quality) Measure (NEPM).

The main legislation governing air quality in New Zealand is the Resource Management Act (RMA), which was introduced in 1991. Under this Act, air quality monitoring and management are the responsibility of regional councils. The New Zealand Ministry for the Environment develops policy and tools to help councils such as the Good Practice Guide for Air Quality Monitoring and Data Management (Ministry for the Environment 2009).

The NZ Ministry for the Environment has also developed a core set of national environmental indicators including key air quality contaminants that are monitored and measured (i.e. small particulates with a diameter less than 10 micrometres, also known as PM10, carbon monoxide, nitrogen dioxide, ground-level ozone and sulphur dioxide).

A major part of the design of the tunnel will be the appropriate dispersion technique adopted for vitiated air. Tunnel dispersion techniques include:

• dispersion from portals

• mechanical longitudinal ventilation and portal dispersion

• dispersion from ventilation outlets

• dispersion by slots.

Section 9.3.2 provides guidance on these dispersion techniques. In addition, guidance may be obtained from Road Tunnels: A Guide to Optimising the Air Quality Impact upon the Environment (PIARC 2008b).



6.4. Water Quality

Water quality issues may arise both during construction and the operation of the tunnel. The Austroads Guide to Road Design Parts 5, 5A and 5B (Austroads 2013) which cover drainage design provides guidance on the control of contaminated run-off water and should be used to design the required systems.

In addition, the design of the tunnel infrastructure must accommodate the requirements of the environmental protection authority in the jurisdiction regarding the control of intercepted ground water or surface water. Further discussion of the details of the design of the drainage system to accommodate contaminated water is included in Section 7.



7. Drainage Design

7.1. General

Drainage design is to be generally in accordance with the Guide to Road Design Parts 5, 5A and 5B: Drainage Design (Austroads 2013). Specific requirements for tunnels are discussed in this section.

The longitudinal drainage system throughout the tunnel and associated ramps should be designed to accommodate stormwater run-off corresponding to a design storm with an average recurrence interval (ARI) which is suitable for the jurisdiction and region in which the tunnel is located. In areas subject to tidal influence an allowance for a rise in sea level due to climate change should be considered. The critical nature of tunnel operation is such that the risk of flooding from external sources should be minimal. A probable maximum flood should be assumed for protection of the portal from flooding, the protection being the design of facilities to prevent the flooding or by way of operating procedures to provide temporary protection measures such as sand bagging.

Drainage for tunnel operations (washing, ground water and seepage) should be designed to prevent ponding on the road surface of the tunnel and to prevent aquaplaning.

The likelihood of coincident stormwater inflows and firefighting inflows should be identified through a risk analysis approach. The results of this risk analysis will determine the magnitude of the storm event which can be combined with firefighting flows, to formulate the credible combination inflow case. This will likely be a frequent event such as the 1 in 1 year ARI or the 1 in 2 year ARI design storm event.

The calculation of expected inflows involves a detailed investigation of the nature and extent of:

• ground water seepage and the drainage of the tunnel structure and lining

• rainfall

• tunnel wall washing

• firefighting (including the activation of a fixed firefighting system)

• wash down following spillages of dangerous goods within the tunnel.

PIARC (2008c) provides information on the assessment of fixed firefighting systems for road tunnels.

A single drainage system should consider the following:

• Specified flood immunity.

• Collection of stormwater run-off at portals and in the tunnel via gullies at appropriate intervals, with longitudinal pipe network to sumps.

• Gullies inside the tunnel to be flameproof and explosion resistant to prevent the possibility of liquid fire being conveyed into the sump via the drainage system. Flame traps are required as part of the tunnel drainage system. Flame traps are integral with a drainage pit and prevent the spread of fire associated with a flammable liquid spill along the drainage system to other drainage pits within the tunnel thereby causing a secondary fire site. The provision of flame traps is to be in accordance with AS 4825: 2011.

• If sumps are sealed and vented to the atmosphere, duty and stand-by pumps should be provided.

• Sump and pump capacity should be designed to be compatible with the inflow rate and pump outflow rate, for a range of possible storm durations and storm severities, up to and including the design ARI for the tunnel’s drainage system.

• Pumps and associated control gear should be designed to operate automatically (via level switches and/or transducers).



• Sumps should be provided with explosion-proof pumps and electrical equipment.

• If sumps are closed with forced ventilation, duty and stand-by extraction fans are required.

• Wastewater complying with effluent standards specified by the relevant authorities and drainage water from the tunnel should be passed through appropriate gross pollutant traps or other environmental treatment systems for capture of hydrocarbons and other undesirable pollutants prior to discharging into waterways.

• The drainage system should be designed to be easily cleaned and maintained; in particular, adequate space is required in all sumps to allow safe cleaning and maintenance of pipes, pumps and all associated equipment.

• Provision should be made for pump operation and systems monitoring at the tunnel control centre.

A free-draining tunnel will deliver economies in drainage costs but the longitudinal profile will not always be amenable to this. Unless the vertical alignment of the road through a tunnel is a crest curve (more achievable in mountain tunnels), it is normally necessary for a road tunnel to be provided with drainage sumps and pumping equipment to collect water from the road surface and discharge it safely.

Where approach roads run downhill towards one or both portals it is normal to provide sumps to intercept stormwater flowing down the approach roads and to prevent it from entering the tunnel. For such cases the catchment areas can be large and consequently portal sumps may instead provide benefits in terms of intercepting run-off before it enters the tunnel proper. Such portal sumps must be sized to accommodate inflow rates and pumped outflow rates for a range of possible storm durations and storm severities, up to and including the design ARI for the tunnel’s drainage system.

In submerged tunnels (immersed tube) or tunnels with low points, grades should preferably not be less than 0.5% to allow any seepage or other water that may occur to flow to a suitably located sump and then be pumped from the tunnel.

7.2. Drainage Systems

7.2.1. Overall Requirements

The tunnel drainage system can be an integral part of the local drainage system, or be designed as a self-contained facility. In general, sag points in tunnels will be well below the levels able to be incorporated directly into existing stormwater drainage systems and will require automated pump-out arrangements. Depending on the quality of the ground water, the tunnel drainage system will collect both ground water and surface water which drains from the tunnel roadways via road gullies and longitudinal drains, and discharges into one or more main sumps. In certain circumstances, where the ground water quality is poor, a separate dedicated drainage system will be required to capture and convey the ground water into a separate ground water sump. An impounding sump or hydrocarbon trap, to contain road tanker spillages and tunnel wash-down water, which is likely to be heavily polluted should also be provided. The requirements of the relevant environmental protection authority must be accommodated.

Pump stations and sumps are normally sited at the lowest point of a sag curve in the tunnel, and near the portals if required. Control rooms or other buildings should not be located near sumps, due to the risk of explosion. Where there is no alternative, full safety precautions must be incorporated into the design of such buildings.

Pump stations, sumps and separators should be sited where they have a minimum effect on the operation of the tunnel, particularly where regular access for their maintenance is required.

Depending on design constraints, the sumps should be outside of the tunnel rather than under the tunnel carriageway.



A pumped system delivers drainage water through single or twin rising mains, passing along the tunnels below the road deck, attached to the tunnel lining or by an external route. Depending on the quality of the pump-out water and on the specific local authority regulations, the rising mains may discharge into a surface water sewer system, into a surface mounted retention tank, into a surface stormwater drainage system or into a watercourse.

The sizing of sumps and separators should consider constraints on available power, size of pumping main, allowable discharge rate and the size of sump that can be accommodated. In sizing the sumps and pumps, the design must consider a broad range of possible storm durations and severities, up to and including the design ARI for the tunnel’s drainage system.

Transverse interceptor drains such as grated trench drains or slotted drains should not be used to remove stormwater as they can accumulate silt and can break up under heavy traffic. Provision should be made for adequate crossfalls in conjunction with gully pits at regular intervals to remove the water and avoid ponding on the approaches to the tunnel.

Tunnel structure drains often become blocked, for example, by calcium compounds leaching out of concrete, ground water salts and silt, construction site debris and build-up of iron bio-films (the specific materials causing blockage are geology dependent and other problems occur in specific geologies such as extensive iron oxide precipitation in Sydney sandstone tunnels). An assessment of the likelihood of clogging of the ground water drainage system should be undertaken, based on water quality measurements. If clogging is anticipated, then appropriate factors of safety should be applied to the calculated ground water inflow rates and oversize drainage pipes should be provided to make allowance for such problems. A minimum pipe diameter of 100 mm should be specified for all ground water pipes.

Inspection chambers should be provided every 60 m to provide for ease of inspection, cleaning and flushing of the drains regularly.

In order that maintenance and repair operations can be carried out without the need for a lane or whole tunnel closure, gully pits should be designed to be suitable for installation in the kerb or in the road shoulder. No part of the gully pit should encroach on the traffic lanes. Inspection chambers should be located in the verge/shoulder for better access and to avoid damage by traffic. Where this is not possible, covers should be positioned outside of wheel tracks. Design data for gully spacing is contained in Austroads (2013).

The drainage system should incorporate appropriate flame traps to limit the spread of any fire that may occur. Details of particular locations are discussed in the following sections.

7.2.2. Sumps, Separators and Pumping Stations

The design of sumps or a series of interconnecting sumps should take account of the following factors.

• provide sufficient capacity

– volume of drainage water

– spillage of flammable and other hazardous liquids

– water for fire purposes (often critical) – Section 7.1, Section 7.5.2 and Section 7.5.6

– flow in excess of maximum pumping rate (large sumps may allow smaller pumps to be used)

• be of adequate structural depth and size

– space for any foam washed into the sump

– space for any floating equipment

– allowance for correct operation of level-detection equipment

– facilities for the pumping plant (Section 7.2.3)

– minimal turbulence around the pumping plant



• include forced ventilation for closed sumps inside the tunnel

– a safe atmosphere for workers

– dilution of any potentially dangerous atmosphere (e.g. accidental spillage)

– removal of any fire extinguishing gases

• allow sumps outside the tunnel to be naturally ventilated

• minimise potential structural damage due to explosion and its transmission to any interconnected sumps.

Interceptors/separators should be:

• of sufficient size to allow adequate separation of pollutants

• designed to provide ease of cleaning

• ventilated to prevent the accumulation of dangerous gases

• designed to minimise the risk of oil or other hydrocarbon substances trapped in the separator being flushed through under high flow conditions.

Sumps should be classified as hazardous areas as defined by AS/NZS 60079.10.1: 2009. All pumps and electrical equipment located in these areas should be designed in accordance with AS/NZS 60079.14: 2009 and related standards.

7.2.3. Pumping Plant

The pumping duties required for a tunnel drainage system will be influenced by a number of factors including:

• the maximum expected inflow to the sump (arising from stormwater run-off from external catchment areas and coincident firefighting inflows – Section 7.1)

• the average normal expected inflow to the sump (arising from stormwater run-off from external catchment areas)

• design constraints imposed by structural works

• maximum discharge limitations and the number of pumps

• discharge system parameters

• the size of the sump.

In addition to the main pumps and electrical motors the following are normally required:

• Motor control gear, cables and transformers – all these items should be installed in a separate non-hazardous area away from the sump.

• Water level sensing equipment to control the starting and stopping of pumps and to generate high water level and flood alarms.

• Hydrocarbon trap or skimming equipment to remove oil or any other liquid that may float on the surface of the water in the collecting sump.

• Hydrocarbon sensing equipment to detect the presence of hydrocarbons in the sump, thereby enabling operator override of the pumping system if required.

• pH sensing equipment to detect the pH value of the stored water and to then identify whether the water is allowed to be pumped to a receiving sewer (applicable to tunnel wash-down water in particular).



• Sludge pumps may be necessary to remove deposits of solid matter in the invert of the sump and thus avoid the need for periodic cleaning by manual labour.

• A reflux (or non-return valve) and an isolating valve should be provided adjacent to each pump. The isolating valve would normally be located downstream of the reflux valve to enable maintenance to be carried out on the latter, as well as the pump. Valves should be situated in an accessible place within the sump, pump room or valve pit.

• Pipe work for connection to a suitable system to permit the sump to be emptied of spillages and removed, independently of the main pumps or discharge pipe work.

• As part of the risk analysis, consideration of the redundancy of the power supply and controls for pump stations.

7.2.4. Discharge Piping

Discharge piping comprises the pipes, valves and fittings situated between the outlets from the pumps and the point of discharge. It may be a single or twin pipe system and incorporate hatch boxes if mechanical cleaning is planned.

Hydraulic analysis should be undertaken to determine the overall operational pumping head through the discharge piping and also to determine transient heads due to other factors such as pump trip, valve closure and the like.

The choice of pipe material type and class must be appropriate for the operational and transient heads throughout the discharge pipe. The adopted material must also satisfy the minimum design life requirements applicable to the tunnel environment (Section 2.4.1).

The choice of pipe materials and protective treatments will depend upon whether the pipe work is buried, cast into the structure or in an open situation. Other factors will be the expected contaminants in the water, costs and ease of installation and maintenance.

The use of plastic and related materials should be avoided in a tunnel as, in the event of fire, toxic fumes could be generated.

Where flood banks or levees form part of the civil works it will be necessary to provide discharge arrangements to ensure that floodwaters are not allowed to flow into the tunnel.

7.2.5. Safety Requirements in Sumps

Typically, bifurcated duty and stand-by extraction fans should be provided in sump areas. Suitable ducting is needed for the supply and exhaust air for the sump. Flame traps as necessary are required to be incorporated.

A suitable fire protection system for the sump should be provided, and appropriate detection mechanisms installed.

The following elements should be designed into the detection and monitoring system (modified from Highways Agency 1999):

• Detection of gas at low and high concentrations should raise an alarm and should also be displayed on the pump control panel. The alarm (high) condition should normally initiate automatic operation of the fire extinguishing system.

• Sampling from one of the gas detection system detectors should take place just above water level.

• The fire extinguishing system should be initiated automatically upon detection by heat detectors of a rise in temperature due to a fire in the sump, and should be operable manually from a local fire control panel.



• The monitoring and surveillance systems should be used to identify spillage of hazardous or other substances which do not give off combustible gases, but which would be undesirable to pump into local water systems. Detection of substances that reduce the amount of oxygen in the atmosphere can be achieved by oxygen deficiency detectors arranged to set alarms when oxygen falls below a pre-set value.

• On detection of a hazardous substance entering a sump, the detection system should switch off the plant to allow manual operation and control.

• All detector sensors should be duplicated and internal detectors should be capable of being replaced in situ as they generally have a short life.

• Sensors need to be water protected.

Sump ventilation air supply and exhaust ducts, where connected into the tunnel atmosphere, should be provided with flame traps. To limit flame passage through the drains in the event of a fuel spillage and fire, U-bends should be incorporated at the inlets to the sump and at the carriageway gully pits where there is adequate access for cleaning the drain. Alternatively, equivalent ‘fire-proof’ drainage systems may be considered.

Open sumps should be accessible to the fire brigade should it need to extinguish any fire.

7.3. Watertable Requirements

The design should ensure that construction activities as well as operation activities are carried out so that any impact on ground water which affects property, public amenity (including settlement that may occur) or existing ground water users is appropriately managed. Where settlement may occur, the tolerable amount of settlement should be assessed and the design determined within that constraint.

Permanent dewatering is not preferred. However, dewatering may be an option in sound rock tunnels where the removal of water from the surrounding area will not create adverse environmental effects. The pumping system for these systems should be designed with sufficient redundancy to ensure that flooding of the tunnel pavements does not occur.

Design specifications should be written to ensure that any dewatering during the carrying out of the construction activities is limited so that it minimises any deterioration of vegetation, ground settlement affecting property or public amenity, and impact on the surface water flows of existing drainage systems.

Any ground water recharge program during the carrying out of the construction activities should be designed and implemented to the satisfaction of the responsible jurisdictional authorities.

7.4. Pollution Control

Run-off from the road will be polluted to some degree from the normal process of road operation and this water will require treatment before being discharged into the wider drainage system. As a minimum, road run-off water should be passed through a hydrocarbon trap and gross pollutant trap prior to discharge into surface stormwater drainage systems or into a watercourse.

Particular attention should be given to the wash-down water from cleaning and accidental spillages. Tunnel wash-down water should be contained in a separate system from the normal stormwater and disposal to a surface sewer is typically recommended, subject to the agreement of the relevant local authority. Accidental spillages should be contained in a separate system or hydrocarbon trap and disposal to a licensed depot via tanker is typically recommended.

Methods of treating polluted water are given in the Guide to Road Design Parts 5, 5A and 5B: Drainage Design (Austroads 2013).



7.5. Calculation of Inflows

7.5.1. General

Inflows to the tunnel structure can arise from:

• rainfall and stormwater run-off

• ground water seepage

• wall washing

• accidental spillage of fuel from damaged vehicles and the wash-down of such products

• operation of fire suppression systems

• accidental rupture of pumped drainage, fire main or hydrant.

7.5.2. Rainfall and Stormwater Run-off

Calculation of the run-off from rainfall should be done in accordance with Austroads (2013). The ARI chosen for the design of the tunnel’s longitudinal drainage system will depend on the particular circumstances of the tunnel in question but inundation of the tunnel structure should be avoided.

Preferably, tunnel portals should have a flood immunity derived from the larger of:

• the probable maximum precipitation event plus an allowance for climate change

• mean high water spring tide, 100-year ARI flood and a 100-year ARI storm surge (where applicable) plus an allowance for climate change

• highest astronomical tide plus an allowance for climate change.

Pump systems provided in the tunnel must be designed for the worst of a 100-year ARI storm event, the requirements of any deluge system, wash-down requirements or for firefighting incident management.

A range of storm durations should be investigated to determine the critical storm duration throughout the drainage system. This is particularly important in determining the optimum size of the sumps and pumps.

Each tunnel should be assessed on a case by case basis using a risk management approach.

7.5.3. Ground Water

Ground water ingress or seepage will occur to some degree in all tunnels. Such seepage is generally collected via spoon drains on the top of the kerbside barriers/behind wall treatments and at the low point of the tunnel cross-section, beneath the pavement. Once collected it should be directed to a dedicated treatment area. Ground water treatment is usually at the surface due to the spatial and maintenance frequency requirements of the equipment. The nature and extent of treatment that will be required depends on the water quality and quantity.

The design should ensure that any ground water seepage into the completed tunnel and associated works is not visible and that no water drips on to the road pavement. For a particular tunnel, the extent of water ingress to be allowed should be assessed on the basis of the environmental requirements and the capacity of the tunnel equipment to accommodate the flows. Ground water seepage to or from existing streams should be such that no unacceptable change in the existing flow regimes occurs as a result of the carrying out of the construction or operation activities. In addition, the potential for settlement occurring as a result of ground water seepage (Section 7.2) should be assessed and appropriate mitigation measures adopted.



The design should ensure that there are no effects of ground water chemistry on the overall tunnel structural integrity or the tunnel drainage system, including the potential for precipitation to reduce the effectiveness of the drainage system, over the design life of the tunnel.

Appropriate treatments should be employed during construction to minimise ground water seepage. Permanent treatments should be employed as required to ensure that any water present on internal surfaces does not affect the safety and function of the tunnels.

7.5.4. Wall Washing

Maintenance wash-down water must be captured by the tunnel stormwater drainage system but could be diverted and treated separately from the ‘clean’ stormwater.

The quantity of water from wall washing operations is dependent on the techniques employed. For purposes of calculation, a water use rate of 5 l/m² of wall area can be used over the period of cleaning.

7.5.5. Accidental Spillage

Spillage of products during incidents will have to be washed down to restore the tunnel to normal operation. This will be polluted water and should be captured separately from the clean stormwater. Most tunnels are equipped with hydrants at frequent intervals, fed from wet fire mains running along their lengths. For such cases, a reasonable allowance would be that two hydrants are used by the fire brigade for wash-down purposes.

7.5.6. Fire Suppression System

For the purposes of design, a deluge system should be assumed and the quantity of water calculated from the known pressure/flow characteristics of the installed system. Alternative suppression systems are being developed (e.g. mist systems).

7.5.7. Accidental Rupture of Pumped Drainage

In cases where a fire main or other part of the pumped drainage system could be vulnerable to damage from a traffic incident or other event, the design of the pumping system should include capacity for the potential outflow from a broken pipe based on its pressure/flow calculations.

7.5.8. Flood Protection

Flood protection at traffic entry points and tunnel ventilation services openings should extend to at least the categories of stormwater and floodwater coming:

• over the sides and portal wall trough structures

• off surface-level overland drainage from connecting roads

• in through the ventilation structural openings.

Where the potential for ingress of stormwater and floodwater into transition/tunnel structures exists, the preferred solution is in the form of a physical levee in and surrounding the carriageways. Mechanical devices, such as floodgates, booms or raiseable barriers are generally not adopted because they involve the risk of malfunction due to debris clogging and jamming mechanisms.



In certain circumstances, a lower level of flood protection may be considered appropriate, provided that due allowance is made to accommodate the expected volume of stormwater which could enter the tunnel. In such instances, the tunnel road surface and drainage system must be designed to safely convey the expected stormwater inflows to the tunnel low point and the low point, sump and pump arrangement must be designed to ensure that the pumping system remains operational during an extreme storm event. This will require an assessment of the expected depth of ponding which could occur during an extreme event, and all mechanical and electrical equipment associated with the pumping system must be located at least 300 mm above that ponded level.

7.5.9. External Hydraulic Impacts

Tunnel entry and exit ramps to surface streets often need to project beyond the existing natural surface levels and therefore have the potential to affect peak water levels for the surrounding areas during flood events. Local authorities generally regulate developments to above a ‘flood regulation level’ of a 100-year ARI event and require developers to demonstrate that their works will not create adverse impacts upon peak flood levels or discharges upon external properties. The appropriate ARI for a particular project should be determined in consultation with the local authority and other relevant authorities.

7.6. Aquaplaning

For vehicle tyres on road surfaces the likelihood of loss of friction due to the depth of water needs to be controlled to avoid instances of aquaplaning. A number of factors influence the potential for aquaplaning in tunnels including location, rainfall intensity (prior to or after the tunnel portals and then carried into the tunnel), likelihood of residual wash-water, posted speed, surface texture and geometry. Typically, aquaplaning potential increases when lower longitudinal grades are combined with low or varying crossfalls. Pavement texture depths used in aquaplaning calculations should be confirmed in conjunction with the finalisation of road surface treatments.

For tunnels, a unique aquaplaning risk may become evident at the exits. It is possible that a safety risk may arise whereby a driver enters the tunnel when the road conditions are dry, only to exit the tunnel finding that the road conditions are wet, due to the onset of a storm while the driver was inside the tunnel. The driver may then be in a situation where the risk of aquaplaning is immediate, but has not had sufficient time to adjust the driving style to suit the conditions. To address this possibility, it is recommended that the maximum aquaplaning film depth be lowered to a desirable depth of 2.5 mm, for a distance of at least 50 m along the exit, measured from the tunnel portal.

Further, it may be appropriate to maintain the tunnel posted speed for a few hundred metres beyond the tunnel portal to allow drivers to adapt to the external conditions.

Designers should refer to the aquaplaning requirements provided in Austroads (2013).



8. Fire Safety

8.1. Overall Approach

The Australian Standard on tunnel fire safety, AS 4825: 2011 is to be used as the basis of the design of the fire safety system for tunnels in Australia and New Zealand. This is a performance-based standard providing a framework for establishing appropriate fire safety systems for road, rail and bus tunnels. The standard provides guidance in the design, construction and operation of a tunnel with respect to fire safety.

The standard:

• sets out performance requirements of the fire safety system

• provides guidance on trial concept design

• provides information on what may constitute appropriate trial concept design for various tunnels

• does not restrict innovative approaches or new technology provided that the required performance can be demonstrated

• outlines what may be appropriate analysis methodology

• allows for both deterministic and probabilistic (risk-based) analysis and approach

• specifies what may constitute appropriate acceptance criteria

• provides general guidelines on system installation and maintenance, which is intended to facilitate making appropriate assumptions in the engineering analysis

• refers to other standards providing greater detail where appropriate.

The standard also states that it does not prescribe an acceptable level of fire safety. It is intended to provide guidance on process and systems to allow the stakeholders to make informed decisions on tunnel fire safety.

Some key elements of the standard include:

• a fire engineering process to guide stakeholders to an acceptable fire safety system

• development of appropriate levels of documentation including a fire engineering brief and a fire safety assessment report

• guidance on issues and design considerations for tunnel fire safety

• performance requirements specific to tunnel fire safety measures

• acceptance criteria for fire safety design

• design-fire information

• fire protection system integration

• details of fire safety systems including related standards and design guides

• installation and construction issues

• testing and commissioning

• maintenance

• emergency management and fire brigade intervention.



8.2. Design Development

8.2.1. General Approach

Tunnel fire safety should be assessed and an appropriate fire safety system developed in accordance with AS 4825: 2011.

The intention of the design is to determine the most appropriate combination of measures to achieve the objectives of the tunnel in question. Adopting one set of measures may allow others to be omitted. AS 4825: 2011 notes a number of strategies for developing an appropriate fire response. These include deluge, detection systems, suppression systems, ventilation and smoke extraction. It should be noted that the important outcome for the tunnel under design is the holistic response under the trial design and conditions generated by following the Australian Standard rather than a comparison of the merits of individual systems. Comparisons of individual systems may not provide the required design solution.

The following overseas documents may provide some guidance on what should be considered, however it should be remembered that Australasian conditions may be different:

• Maevski (2011)

• Hall (2006).

8.2.2. Prevention

Prevention of incidents is preferable to dealing with the consequences. Prevention techniques include:

• careful design of tunnel cross-section and alignment including sight lines and grades

• suitable lighting levels and portal illumination

• limiting the amount of combustibles and using fire retardant materials

• driver warning systems (e.g. radio re-broadcast)

• operational response to transport of hazardous materials

• education of users

• physical prevention of vehicles entering the tunnel by movable barriers

• over-height barriers prior to and at portals

• nomination and enforcement of speed restrictions (including permanently installed speed cameras)

• high system reliability including back-up systems and redundancy such as dual water supplies, dual and uninterruptible power supplies.

8.2.3. Evacuation

Fire separation

An evacuation strategy should be based on moving to a ‘place of ultimate safety’ and this may be undertaken in stages reducing the risk at each stage. In twin tube tunnels this strategy is based on moving from the incident to non-incident tunnel tube using cross-passages; hence fire separation between tunnel tubes is necessary.

Other tunnel types, or where the non-incident tube is inaccessible, may require a dedicated emergency escape tunnel or a direct escape path to the surface.



In short tunnels, the tendency will be for the road users to exit through the portals in times of emergency. An adequately lit route (walkway or roadway) to the portals should be provided and preferably signalisation provided to stop entry into the tunnel.

Entry control

Control of traffic entering the tunnel may be required for a range of reasons, for example:

• during periods of maintenance in the tunnel

• at times when congestion may threaten to overload the ventilation system

• when relief is required in the event of an incident.

The means of this control should be determined by the specific requirements of the site and may include traffic signals and signs positioned to stop traffic from using one, two or all lanes in the tunnel.

Appropriate signals and signs remote from the tunnel (prior to the decision point to use the tunnel) may also be required to divert traffic to alternative routes in times of closure of the tunnel.

When cross-passages are used, the traffic in the incident-free tube also may need to be stopped so that any evacuees may enter that tube safely. This needs to be balanced with the need for emergency services to access the fire from the non-incident tunnel. Opening of the cross-passage doors to the other tube may be controlled by the tunnel control centre and telephones in the cross-passages may be used to communicate with evacuees and advise them when it is safe to open the doors. Alternatively, the doors may be located in a recess in the tunnel wall providing some protection from any vehicles that may still be in the adjacent tube. The option used will depend on the tunnel characteristics, time of day, traffic density, type of incident, etc.

For busway tunnels, direct communication with bus drivers should be available to control the movement of buses (e.g. diverting them to alternative routes when excessive delays in the tunnel occur for whatever reason).

Pedestrians

Pedestrian walkways, cross-passages and longitudinal passages in vehicular tunnels are generally provided as a path for exit in an emergency and lead to other locations to achieve a place of ultimate safety.

Pedestrian emergency escape tunnels parallel to the vehicular tunnel and pedestrian refuge areas with independent air from the surface have been provided in some major tunnels (Rechnitzer et al. 1999). In some circumstances, remaining in the vehicle may be the preferred option but only if directed to do so by the tunnel control centre. This allows drivers to hear radio re-broadcast (where provided) or loudspeaker broadcast of emergency instructions.

Weaving through stopped traffic to an emergency cross-passage may also be difficult for evacuees on foot as:

• shoulders and walkways may be unusable due to vehicles not stopping directly within a lane

• spacing between stopped vehicles may not permit wheelchairs to pass through

• vehicle doors may be left open blocking the path between lanes to a cross-passage

• vehicles may try to undertake U-turns and cause disruption.

Cyclists

In those rare cases where cyclists are permitted to use a tunnel, their means of evacuation will be the same as those for pedestrians.



Mobility impaired persons

It is essential that the design provides an emergency walkway that is accessible to road users who may have mobility impairment (drivers or passengers). Refer also to the section on pedestrians above.

Holding areas

Where holding areas for mobility impaired persons and others are provided, the cross-passage and/or stairs are no longer just transit zones but become akin to a refuge. Therefore positive ventilation is required to prevent the ingress of smoke and other toxic gases.



9. Ventilation Design

9.1. General


The general requirements for ventilation design are described in the Guide to Road Tunnels Part 1: Introduction to Road Tunnels (Austroads 2018a). This section provides details of the design required including standards to be achieved and preferred systems of ventilation for Australian and New Zealand tunnels. Further guidance may be obtained from PIARC (2012a): Vehicle Emissions and Air Demand for Ventilation as well as PIARC (2011): Operating Strategies for Emergency Ventilation.

9.1.2. Assessing Ventilation Needs

An assessment of the needs of a tunnel ventilation system should be based on:

• providing a safe environment for tunnel users with adequate protection from the effects of vehicle emissions

• providing adequate visibility for the purposes of collision avoidance and way finding, by preventing the accumulation of particulates arising from vehicle exhausts, tyre wear and dust (note that amenity concerns may be raised at lower levels)

• providing a tenable environment for tunnel users during a fire while minimising the risk of fire growth and fire spread

• controlling the dispersal of tunnel pollutants to the atmosphere.

As part of the analysis of factors that determine fresh air requirements for the dilution of vehicle pollutants, consideration should be given to establishing the tunnel ventilation capacity available to control the direction of smoke and assist evacuation and firefighting procedures, including pressurisation of cross-passages (refer to Section 8). This should also consider the peak ventilation energy consumption and its effect on the likely electricity tariff with a view to optimising the system.

A detailed discussion of the objectives of ventilation in both normal and emergency operation is provided in PIARC (2011).

PIARC (2012a) provides a detailed method for calculating emissions and provides emission factors appropriate to Australia and New Zealand for CO, NOx and opacity. Practitioners should use this publication for assessing ventilation needs in tunnels.

9.1.3. Mechanical Ventilation

A mechanical ventilation system is an important facility for maintaining acceptable in-tunnel air quality and safe conditions in the event of a tunnel fire.

The relationship between the following factors is relevant in deciding the most appropriate ventilation regime:

• the length of the tunnel

• distance to emergency exits

• highway gradients

• the traffic (one-way, two-way, volume and composition with respect to percentage of heavy vehicles)

• transport of dangerous goods

• safety installations

• the planned response to emergencies.



The actual number of vehicles in a tunnel at any one moment will depend on the average vehicle speed and the traffic density. Typically, as traffic slows, the total number of vehicles within a tunnel will increase. The vehicle-induced air movement referred to as ‘the piston effect’ is significantly reduced at lower traffic speeds. A larger number of vehicles will increase the total drag resistance to air movements and the generation of exhaust fumes. Many tunnels are likely to be self-ventilating for long periods when traffic is flowing freely, but can lose almost all of their self-ventilating capacity when traffic speeds are reduced, during peak hours, breakdowns or other incidents.

In general, a minimum of four broad operational regimes need to be considered for ventilation design:

• free-flowing traffic (for example, average speeds of 50–80 km/h)

• network constraint-driven congestion (for example, average speeds of 20–40 km/h)

• incident/breakdown-driven congestion (for example, average speeds less than 20 km/h on a sustained basis)

• smoke extraction during a fire incident.

It should be noted that the first two cases do not result in any credible potential smoke exposure to motorists downstream of a fire in a longitudinally ventilated system but that the third case needs careful consideration in the event of fires behind an initial incident/breakdown.

In addition, vehicle operation is less efficient in congested conditions, increasing pollution rates.

9.1.4. Performance Objectives

The tunnel ventilation system should meet the air quality requirements described in the recommendations of the Permanent International Association of Road Congresses (PIARC) 2, jurisdictional work safe exposure standards and environmental requirements as defined in relevant regulatory authority approvals. In the event of any inconsistencies between these requirements, the appropriate value relevant to the circumstances of the tunnel in question should be adopted.

The tunnel ventilation system should be able to be operated to meet specified in-tunnel and external air quality requirements under credible atmospheric and traffic flow scenarios (refer to Section 9.3). Care should always be taken to ensure that the combination of requirements is reasonably credible and not just that each requirement is credible in itself (e.g. a major fire with a combination of an HV power failure with an adverse wind event may not be really credible even though each sub-event is credible on its own). Risk analysis should be undertaken to establish the credible scenarios.

9.1.5. Factors Affecting Ventilation System Performance

Meteorological effects

Meteorological records for the area should be obtained, so that the ventilation system performance can be assessed in the worst likely conditions of wind, wind direction, humidity and extremes of temperature. The effect of the immediate local topography should also be considered.

The cases to be studied should include:

• weather conditions adversely affecting the tunnel environment

• weather conditions adversely affecting the dispersion of airborne pollutants from the tunnel.

2 The NZ in-tunnel air quality requirements are incorporated in the Guide to Road Tunnels (NZ Transport Agency 2013b).



The former is likely to happen at high wind speeds (often in excess of 10 m/s) and the latter at comparatively low wind speeds (often around 2 m/s). The atmospheric stability cannot be assumed only to be neutral. Relevant historical data such as wind roses can be useful for analysis.

Ambient wind conditions will need to be considered for the design ventilation capacity. Ambient wind is particularly relevant for short tunnels where the wind effects may completely dominate the designed ventilation system. To limit ambient wind effects, strategies such as modifying the tunnel alignment relative to the prevailing wind, or providing wind protection around the portals may be used.

The background levels of ambient air contamination should be taken into account when assessing pollution levels. These levels may be obtained by a local survey and applying appropriate design year predictions. The levels assumed should be clearly stated and agreed with the appropriate regulating authority. It should be noted that background levels are highly variable and a reasonably representative value (e.g. 75th–90th percentile or similar) rather than an absolute peak value should be used to avoid overstating the background contribution.

9.2. Systems of Tunnel Ventilation

There are several types of ventilation systems that have been proven effective in use. Many factors have an influence on the choice of a ventilation system and should be taken due account of in accordance with their relative importance to a particular scheme. The end result for a ventilation system is that it is aerodynamically sound, provides satisfactory environmental conditions inside the tunnel and adjacent to it, manages smoke in the event of fire, has acceptable capital and running costs, and satisfies the operator in terms of control, maintenance and cleaning. Smoke ducts may be required to control smoke where there is a likelihood of stopped traffic and a fire.

Types of ventilation systems are:

• vehicle piston effect

• longitudinal

• fully transverse

• semi transverse

• hybrid (combination).

Refer also to PIARC (2011). Appendix B includes the general classification system adopted by PIARC (2011).

9.3. Air Quality Management

9.3.1. Internal Tunnel Requirements

Section 6.3.1 discusses the factors to be considered for in-tunnel air quality. The design of the ventilation system should consider these factors.

9.3.2. External Air Quality

Section 6.3.1 provides guidance on the requirements for external air quality. Dispersion of vitiated air from the tunnel will need to be designed to meet these requirements. Dispersion methods are also discussed in Section 6.3.2.



Dispersion from portals

The acceptability of the portal dispersion performance will depend upon the air quality standards which must be met. Dispersion of emissions from portals is commonly considered to be an acceptable way of dealing with the disposal of pollutants. Even for some long tunnels (refer to Section 2.2 of the Guide to Road Tunnels Part 1: Introduction to Road Tunnels (Austroads 2018a), disposal in this way may result in acceptable air quality at sensitive receptors provided they are at a sufficient distance from or appropriately located relative to the portals, particularly during periods of low traffic flow (e.g. at night) or periods of good dispersion conditions (PIARC 2008b). Rational analysis based on realistic design scenarios without excessive conservatism is required for good decision making on this topic.

Mechanical longitudinal ventilation and portal dispersion

In one-way tunnels the combination of vehicle driven ventilation caused by the ‘piston effect’ and mechanical ventilation leads to a concentration profile as shown in Figure 9.1.

Where air velocities are in the range of 3–5 m/s mechanical longitudinal ventilation can raise the ventilation velocity to approximately 6–8 m/s although plant requirements and energy consumption rise at an exponential rate with increasing design velocity. This will lower the concentration of emissions at the exit portal although the environmental costs in terms of energy consumption and noise protection should be considered (PIARC 2008b).

Due to safety concerns and energy considerations in one-way tunnels, it is not advised to ventilate against the direction of traffic in order to manage dispersal at the entrance portal.

In two-way tunnels it is, in principle, possible to utilise the longitudinal ventilation system to control the dispersion of air at either portal. However, the safety implications should be considered.

Figure 9.1: ‘Idealised’ concentration profile in a longitudinal ventilated tunnel (reality may be substantially more complex)

Source: PIARC (2008b).

Dispersion from ventilation structures

In broad terms, collecting emissions and venting them via ventilation outlets, as illustrated in Figure 9.2, is a very efficient way of dispersing pollutants. Comparative studies show that the process of removing surface traffic from heavily trafficked roads and disposing of the same amount of pollution from, for example, a 20 m ventilation outlet results in substantially lower concentrations at all sensitive receptors (PIARC 2008b).



Discharges of vehicle emissions via appropriately designed ventilation structures will ensure that emissions are dispersed and diluted so that there is minimal or no measurable effect on local ambient air quality. The location, height, and efflux velocity of ventilation structures largely controls their effectiveness in terms of air pollution control. In particular, to ensure adequate dispersion and dilution, ventilation structures should be sufficiently higher than surrounding buildings (proximity of these buildings is an important factor). Actual outlet heights need to be established with consideration of local conditions such as topography and urban form. For example, it is particularly important to avoid valleys and other areas of poor dispersion, and locating outlets (ventilation structures) in sensitive receiving environments (e.g. near residences, schools, etc.) or other locations with unfavourable meteorological characteristics, e.g. street canyons.

Ventilation structures are generally only required for longer tunnels in urban areas with high traffic flows due to the potential for elevated levels of vehicle emissions to accumulate inside the tunnel at certain times.

For tunnels with a ventilation structure, at times of free-flowing traffic co-incident with low traffic volumes and favourable external weather and air quality conditions, it may be appropriate to limit the use of the ventilation structure and discharge emissions via the portals. Poor architectural design of the ventilation structure and associated buildings will create a visual intrusion which may accentuate public concerns regarding air quality associated with the tunnel.

Short tunnels will generally not need a ventilation structure where one or more of the following characteristics are met; free-flowing traffic, relatively low traffic volumes; few, if any, highly sensitive air pollution land uses nearby; or located where there is good background ambient air quality. In such circumstances, portal emissions are the most appropriate means of discharging vehicle emissions to the external atmosphere.

Significant cost savings can be made by avoiding inappropriate ventilation system design requirements, for example ‘no portal emissions’ where such a restraint is unnecessary and through the energy-efficient use of the ventilation system during normal operation.

For many single-direction tunnels the piston effect is frequently sufficient to ensure compliance with in-tunnel air quality criteria and the use of the ventilation system can be minimised. It is essential that the use of the ventilation system is carefully managed and monitored to ensure efficient and effective operation.

Figure 9.2: Illustrative schematic of an outlet near an exit portal

** Airflow depending on the tunnel design. In some situations, portal emissions are permitted.

Note: d = 6 – 8 hydraulic diameters (hydraulic diameter = 4 x cross-sectional area/ perimeter).

Source: Modified from PIARC (2008b).



It is rare that only one ventilation outlet is used for a long tunnel. Multiple outlets are an option to spread the vitiated air over several dispersion points and are usually required for long tunnels (refer to Section 2.2, Austroads 2018a) due to the practical limitations on achievable longitudinal airflows within a practically constructible tunnel cross-section (illustrated in Figure 9.3). Complicating factors such as social concerns, terrain and high-rise buildings can constrain the location of outlets.

Figure 9.3: Example of multiple outlets for air exchange system

Note: This type of system is used for very long tunnels, or those with high ventilation demands. These outlets may also be included in semi-transverse systems.


Dispersion by slots

Open slots provide an opportunity to vent a tunnel by natural ventilation. The position and dimensions of the slots should result in acceptable air quality near each slot and the tunnel portals. This option provides a favourable solution if stacks are impossible or undesirable. The option does not provide a substantial benefit over an open roadway from an air pollution point of view although it may have other benefits such as reduced noise and improved social amenity. Figure 9.4 provides one example. Both dispersion of emissions and fire performance would need extensive modelling to ensure adequate performance under all conditions.

Figure 9.4: Schematic example of slots in the roof, including sound attenuators


The use of large openings in the tunnel roof provides opportunities for large volumes of air to be vented in a fire. Although dispersion of contaminants is similar to a surface road, the satisfactory performance of the tunnel in terms of fire safety by the use of buoyancy-driven natural airflows alone can be achieved with a high degree of reliability in some cases with careful design. Such an approach would require regular and frequent openings. Figure 9.5 illustrates this.

Sound barriers (optional)



Figure 9.5: Natural ventilation by using large gaps


An example using many small gaps is shown in Figure 9.6.

Figure 9.6: Natural ventilation by using small repeating gaps in the roof


9.4. Fans

Axial fans

Axial flow main fans are used in ventilating major road tunnels. Capacities are typically in excess of 100 m3/s. The large diameter fans are located in fan rooms with connecting shafts supplying and extracting air to or from the tunnel system. Such fans may supply or extract air for a tunnel section or its full length depending on tunnel parameters (e.g. length, geometry, location, traffic volume).

An axial fan is one in which air passes between aerodynamically shaped blades to enter and exit axially to the direction of rotation. Reverse flow may be achieved by reversing the direction of rotation of the motor. An axial fan with blades set to be optimised for a specific flow direction will produce a reduced volume when the motor is reversed and may have a limited design life for this duty. Volume control and reversibility can also be achieved using fans with variable pitch blades. Variable speed drives are another method of providing volume control.

Centrifugal fans

Centrifugal fans have different pressure, flow and spatial characteristics from axial fans. Typically, centrifugal fans have not been used in modern tunnel airflow control as they require more space than axial fans of the same duty, and reverse airflow can only be achieved by use of dampers and a reversing duct arrangement. Centrifugal fans have some advantages over axial fans as they are more efficient and less noisy and provide higher pressure capability.



Jet fans

Jet fans are relatively small in output and size and can be housed in groups within the tunnel, spaced lengthwise in series to give a multi-fan longitudinal air flow, or at the tunnel entrance as blowers. The fans are of the horizontally mounted, axial impulse type and maintain a longitudinal velocity of air within a tunnel. A jet fan increases the velocity of the air mass that the ‘air jet’ passes through. The subsequent exchange of momentum between the high velocity jet (typically between 30 and 35 m/s) and the slow moving air within the traffic space is used to maintain the required overall air velocity for ventilation and smoke movement. The following should be noted:

• Jet fans are not as efficient as axial fans operating in a ducted system. However, low capital cost and simplicity of installation and maintenance may justify their use.

• The distance between fans in the longitudinal direction of the tunnel requires careful consideration and should be spaced to prevent the flow from one fan reducing the performance of another. Similarly, signs and other equipment should be located to avoid reducing the performance of the fans.

• Fans should be provided with anti-vibration mountings which should be fail safe, e.g. by providing safety chains to prevent the fans falling onto traffic in the event of failure of a fixing. Vibration monitoring for determining service requirement purposes should be considered as follows:

– care should be taken to avoid galvanic and other corrosion of any fixings

– water entering a jet fan from any source (e.g. washing activities) will need to drain out

– sealed-for-life bearings should also be considered

– self-cleaning blade shapes may be beneficial in reducing maintenance needs.

• Jet fans act by the combined effect of many fans. The design should make provision for a loss of output from a certain number of fans (in maintenance and fire conditions) without jeopardising the overall minimum airflow.

• Jet fans can be located at various places in the tunnel cross-section. They are most efficient when located at a distance of three fan diameters from a continuous surface. Fans in ceiling or wall recesses are not desirable for loss of ventilation efficiency reasons, and particularly at corner locations, but may be justified economically compared with alternatives that incur higher civil construction costs, particularly for immersed tube tunnels. Deflector blades at the air jet exit can be beneficial in reducing energy losses at such locations. Inclining fans at a small angle (around 5–10 degrees) may increase efficiency. For reverse flow, a facility to reverse the inclination angle would be required.

• A comprehensive ventilation study should be undertaken to balance

– initial, maintenance and operational costs for a given traffic flow

– the probabilities of each critical scenario occurring simultaneously

– collective fan noise.

• The study should take into account

– the number of fan groups

– their transverse alignment or staggering, together with details of any niche recess shapes

– all efficiency losses, ensuring local re-circulation does not occur

– cabling and maintenance requirements

– any functional loss during a fire.

Table 9.1 is a guide to the distances within which jet fans may be destroyed during particular sizes of fire.



Table 9.1: Distances over which jet fans may be considered destroyed during fire

Fire size (MW) Distance upstream of fire (m) Distance downstream of fire (m)

5 – –

20 10 40

50 20 80

100 30 120

Note: This table does not take account of the installation of a deluge system. In practice, only fans directly affected by flames are likely to be destroyed.

Source: Highways Agency (1999).

Fan reversibility

Fans for tunnel air control may need to be reversible in order to:

• provide for the case where one tube of a twin tunnel has to be used for two-way traffic or one-way traffic in the other direction

• provide for air-flow reversal in a two-way tunnel to accommodate significant changes in the direction of the predominant traffic flow

• allow for smoke extraction in an emergency situation

• maintain over-pressure in the non-incident tunnel.

9.4.1. Noise

Ventilation equipment can be a major source of noise in tunnels and therefore limitation of noise emission is an important factor in the choice of fans. Acoustic treatment by means of inlet and outlet silencers and/or casings with sound-absorbent lining may be required in order to reduce the amount of fan noise transmitted to the outside environment. ‘Break-out’ noise may occur in vent stations and other structures housing equipment and this will have to be limited to achieve the required noise environment.

Careful attention to the detailed design of ventilation equipment will achieve the required sound levels at lower cost to the end user than the use of sound-attenuating equipment. The sound power level of a fan increases very rapidly with increasing tip speed. For a given volume of air, a larger and slower rotating fan will be quieter (but more susceptible to stall). Similarly, reductions in mechanical noise can be achieved from such things as efficient design of motor couplings, driving gear and adequate stiffening of the casing.

Reduction in air path noise is obtained by careful duct design with the minimum amount of turbulent flow from sharp bends and obstructions.

Mounting of machinery on insulated bases will reduce transmission of noise and other vibrations through the ground.

For jet fans, additional sound-absorbent material in the fan casing, and inlet or outlet silencers should be considered. Any increased head loss caused by a silencer, in some designs, can only be compensated for by increased fan energy consumption and hence higher potential noise levels. Lower jet velocities of 20 m/s are quieter but increase the size and number of fans. A balance has to be determined during the design.

To avoid interference with emergency communication systems, fan noise inside road tunnels should not exceed a maximum noise rating of NR85 at a plane 1.5 m above the road surface. In-tunnel noise requirements need to be coordinated with the tunnel public address and evacuation system to ensure that the emergency messages produced are intelligible.



It should also be noted that the silencers on jet fans may become blocked with solid particulates over time. When this occurs, the silencer’s attenuation properties may be adversely affected. To greatly simplify the removal of jet fans for silencer cleaning, or routine maintenance, each jet fan should have its own dedicated local electrical isolation switch and a waterproof electrical connection plug.

Reference should also be made to Section 6.1 for discussion on environmental considerations.

9.4.2. Ventilation System Safeguards

The essential nature of the ventilation system requires that it be kept operational under almost all circumstances. It is therefore necessary to build in reasonable safeguards to avoid unplanned closure or undue restrictions on traffic flow. The following features should be considered:

• redundancy of essential equipment

• two separate sources of electricity supply (Section 11)

• stand-by fans to account for fan breakdown or unavailability

• redundancy to accommodate a fire situation.

Operational requirements are discussed in detail in Guide to Road Tunnels Part 3: Operation and Maintenance (Austroads 2018b).



10. Lighting Design

10.1. Overview

A high standard of lighting is provided in road tunnels to enable users of the tunnel to see their way and to identify potential hazards quickly.

The lighting systems for road tunnels will include lighting the tunnel interior, tunnel approaches and parting zones, emergency access passages, and plant and equipment rooms.

The elements of a road tunnel lighting system include:

• external road lighting (AS/NZS 1158.1.1: 2005)

• tunnel lighting system (AS/NZS 1158.5: 2007)

• emergency cross passage and egress passage lighting (AS 2293: Set-2005)

• building lighting (AS/NZS 1680.1: 2006; AS/NZS 1680.2.1: 2008; AS/NZS 1680.2.2: 2008; AS/NZS 1680.2.4: 1997).

System components include:

• tunnel luminaires (AS/NZS 60598.2.3:2015, SA/SNZ TS 1158.6:2015 and AS/NZS 60598.1: 2003; AS/NZS 60598.2.1: 2014; AS/NZS 60598.2.22: 2005)

• photometers

• lighting sub-circuits

• miscellaneous tunnel lighting

• lighting distribution boards

• lighting control system.

The tunnel classification in Table 2.1 of AS/NZS 1158.5: 2007 is intended only for the purpose of lighting design and should not influence the classification of tunnels for the Guide.

Decisions relating to tunnel length, location, orientation, cross-sectional profile, approach-road conditions, design speed, surface finishes and the structure and form of the portals are important factors that affect the detailed design and cost of tunnel lighting. Early consideration should be given to these factors and tunnel operation and maintenance procedures. The quality and height of the reflective interior wall or lining finishes together with the lighting design strongly influence the driver’s sense of safety and comfort about tunnel-driving safety.

There are three commonly used lighting systems in tunnels:

• Symmetric lighting: where the light falls equally on objects in directions with and against traffic.

• Counter-beam lighting: where the light falls on objects from the opposite direction to the traffic.

• Pro-beam lighting: where the light falls on objects in the same direction as the traffic.

Symmetric lighting provides the best quality of tunnel lighting and the best level of comfort and visibility for drivers, and is recommended for all tunnels.



10.2. Lighting Zones

Tunnel entrance (consisting of threshold and transition zones), interior and exit zones should provide the various lighting levels respectively in accordance with AS/NZS 1158.5: 2007. This standard also addresses the lighting of the access and parting zones immediately outside of the tunnel portals. The lighting design in entry zones should provide high levels of lighting corresponding to the daylight intensity to assist driver-viewing adaptation from bright daylight to the relatively darker tunnel environment. Booster lighting is provided at exit portals to assist rear view visibility (Figure 10.1).

Luminaires in these zones should therefore be controlled and the lighting levels automatically regulated by photometers monitoring the real-time ambient light levels outside the tunnel entry portals. The plant management and control system (PMCS) should provide an alternative backup ‘time of day’ clock system based on seasonal and latitudinal variations of lighting in case of photometer failure.

Figure 10.1: The zones in a long tunnel

Source: Based on Figure 3.1 of AS 1158.5: 2007.

10.3. Spacing and Location of Luminaires

10.3.1. General

The objective of the placing of luminaires is to produce as even a distribution of light as possible on the road and walls of the tunnel.

Luminaires should be located so as to permit simple and easy access for cleaning, re-lamping and complete replacement when required. Luminaires should also be appropriately placed to minimise shadowing by tall vehicles.

10.3.2. Centrally Mounted Luminaires

For basic lighting, fluorescent luminaires mounted continuously end to end, can provide a high quality lighting system with good comfort and visibility for drivers. Lighting utilising only high pressure sodium (HPS) luminaires is also used successfully in tunnels.

Additional lighting required to reinforce the entrance and exit zones is achieved by the addition of further adjacent lines of luminaires. HPS luminaires are generally used for boost lighting at the portals.

In a two-lane tunnel, access to luminaires is likely to require complete closure of the tunnel since both lanes may be obstructed. Offset lighting may avoid this issue if it is practicable to use it.



10.3.3. Side Mounted Luminaires

Side mounted luminaires, with luminaires mounted on both sides of the tunnel, are often used when there is restricted vertical clearance. Mounting luminaires on each side of the carriageway offers the additional benefit of maintenance access if safety considerations permit traffic flow in the remaining lanes.

10.3.4. Visual Flicker

Visual flicker (impression of flashing lighting), caused by spacing luminaires at certain intervals, may lead to discomfort or distress for drivers passing through the tunnel. Accordingly, the lighting design should comply with the requirements of AS/NZS 1158.5: 2007, Part 5, Clause 3.3.8.

10.4. Surface Reflectance

The efficient lighting of the tunnel depends on the reflectance of the wall and road surfaces to provide an acceptable distribution of the light. Figure 10.2 shows an example of a tunnel where light is reflected from the walls and pavement whilst Figure 10.3 illustrates the distribution of light within a tunnel cross-section.

Design of the tunnel approach areas is an important consideration in the tunnel entrance luminance requirements. Factors including urban design, low reflectance of portal surrounding surfaces, retaining walls, asphalt road surfaces, trees and extended facades, assist in the reduction of the tunnel entrance luminance requirements with consequent energy saving.

At the tunnel entrance the proportion of the sky visible to the driver is a significant factor in the determination of the tunnel entrance lighting level. Therefore the approach gradients, shielding and other provisions should be considered.

Effects of low sun angles should be considered in the tunnel orientation and portal design as this can have a marked effect on visibility for drivers entering and/or leaving the tunnel.

The design of the entire tunnel lighting should achieve and maintain the required luminance under normal operating conditions making due allowance for luminaire performance reduction (due to life-cycle depreciation factors) and variations to tunnel wall reflectance values.

The tunnel wall linings should be of high reflectivity and semi-specular finish. The choice of road surface has significant impact on the luminance yield in the tunnel. For instance a concrete surface (reflectance R1, refer to AS/NZS 1158.1.2: 2010) will only require 70% of the light required for an R3 asphalt surface. This leads to significant power savings and will reduce the number of luminaires required. The effect on lighting reflectance should be taken into account with any proposal to change the road surface from that for which the lighting was originally designed.

The visible tunnel lining may be either a structural concrete lining or a secondary lining and must be of the same appearance on both sides of the carriageway.

The tunnel lining and road surface materials should be selected considering their surface reflection characteristics.

Where a secondary lining is used, including any fixing system, it should:

• be continuous above the traffic barrier or footway to a height sufficient to provide the reflectance required above the roadway

• be durable, non-distorting and appropriately surfaced to provide surface reflectance greater than 60% for the full service life of the lining (vitreous enamel coating or suitable painting).



Figure 10.2: Example of light reflected from wall and road surfaces


Figure 10.3: Light distribution

Source: Highways Agency (1999).



10.5. Other Requirements

10.5.1. Essential Lighting Supply

The electrical supply should comply with AS/NZS 1158.5: 2007, Section 5, which specifies lighting power supply requirements for various types of tunnels. For long tunnels, the lighting sub-circuits should be arranged so that half of the tunnel lighting (each alternate luminaire or alternate adjacent rows of luminaires) within any one electrical distribution zone remains unaffected by loss of power supply from any one substation main distribution board.

Since total failure of the power supply will result in total loss of tunnel lighting, careful consideration should be given to the probability of supply failure and the operational requirements in such an event. The mains failure lighting provisions of AS/NZS 1158.5: 2007, Clause 5.1.7 apply. These provisions will provide sufficient light for safe evacuation of the tunnel, but not for continued operation with traffic.

Where tunnel closure is unacceptable, sufficient standby lighting should be provided to permit the safe passage of traffic, with an appropriate signed speed restriction.

10.5.2. Emergency and Egress Passage Lighting

Both the route to the egress and the entrance to the egress should be clear to users. The egress passage must also be adequately lit to allow the safe exit of evacuating people. These conditions may be achieved by application of the following requirements.

Emergency egress door lighting should include:

• exit lighting designed to AS 2293: Set-2005

• strobe lights at each door location (where specified, door location lights above the door and either side of the door using white strobe lights with a strength no less than 300 ecd; strobe lights at either side of the door must be no higher than 1.5 m from the top of the pavement level)

• a downlight at each door location.

Passage and stair lighting should include:

• general lighting designed to AS/NZS 1680.1: 2006

• exit, emergency and directional lighting designed to AS 2293: Set-2005

• connections to separate essential lighting circuits

• local controls and remote controls through the PMCS.

In addition to these requirements, a separate low-level emergency lighting system complying with AS 2293: Set-2005 should be provided (note that this implies that the system is connected to an uninterruptible power supply – UPS). This system should be effective without any contribution from the overhead general lighting system and will generally incorporate fluorescent lighting on both sides of the vehicular tunnels. The luminaires should be fully recessed into the tunnel architectural panels (or positioned to ensure they are not a hazard to pedestrians) and each located to adequately light the footpath. A sign should be fixed to the barrier directly below the luminaire location, advising of the distances in both directions to the closest egress.

10.5.3. Luminaire Enclosures

Luminaire enclosure rating should conform to IP 65 over its entire life in accordance with AS 60529: 2004.



10.5.4. Lighting Control

The monitoring and control of tunnel lighting based on measuring external lighting values, using luminance (i.e. light incidence on surfaces) should be adopted as this method is more precise for energy cost control. A monitoring system using appropriate measuring equipment should be designed to provide for the requirements set out in the Guide to Road Tunnels Part 3: Operation and Maintenance (Austroads 2018b).

10.5.5. Future Developments

Design of the lighting system should allow for the installation of reliable LED (light emitting diode) lighting for road, tunnel and egress passage lighting.

Notwithstanding the need to abide by current Australian and New Zealand standards, innovative lighting systems are being developed in various parts of the world and designers should be cognisant of the potential for adopting these innovations or providing designs that can be readily modified to incorporate such innovations. Pursuit of systems that require lower energy consumption, require less frequent replacement and are more easily activated is encouraged.



11. Electrical Supply Design

11.1. General

A wide range of electrical/mechanical equipment is installed within many road tunnels to maintain the required level of safety for road users, operational and maintenance personnel and emergency services personnel. The main equipment typically comprises high voltage (HV) and low voltage (LV) switchgear, transformers, distribution boards and uninterruptible power supply (UPS) systems. Substation spacing is generally driven by a balance of civil engineering costs, cable costs and electrical load distribution.

In many cases, the high voltage supply is from the main grid HV supply at a voltage determined by HV system design and approved by the electrical supply authorities. It is important that the HV supply is from two separate supply authority substations or different zones of the grid. The low voltage is generally 400 V (415 V), although higher voltages have been used in Australia due to the type of loads.

Risk assessment cognisant of the relevant project-based constraints may determine the power distribution configuration particularly for shorter or remote tunnels.

Incoming supplies and key items of equipment such as main distribution cables and transformers must be duplicated with an automatic changeover facility, and appropriately sized so that if one is out of service, either because of a fault or for maintenance, service can be maintained via the other for as long as necessary.

In addition, arrangements should be made to ensure continuity of supply in the event that both sources of supply fail and that essential equipment remains operable for a suitable time.

The electrical requirements should be assessed for each main area of demand (lighting, ventilation, pumping and the remainder of the installation) to determine the total connected demand load in kVA and the likely maximum demand. This will enable the supply capacity and the ratings of the plant (transformers, switchgear and cabling) to be established. Supply authorities should be consulted at the planning stage about the estimated installed load for all tunnel electrical equipment (lighting, pumps, fans, etc.). Information for discussion should include sufficient predicted load profiles, plotted against time over typical 24-hour periods and any seasonal variations as well as peak demands during an emergency. This will then allow the most appropriate connection points to the electricity grid to be determined and the power authority to accommodate the planned tunnel loads in power network grid upgrades.

A power supply report should be produced addressing the following issues:

• supply arrangements for critical, essential and non-essential loads

• supply arrangements during the various emergency scenarios

• standby generating equipment interlocks with normal mains supply.

11.2. Tunnel Electrical Supply System

11.2.1. General

Two HV supplies from the supply authority to the LV distribution board should be sized so that full tunnel and roadway operations are maintained in the event of the failure of one supply.

Sufficient UPS capacity should be provided to allow safe egress and safe shutdown of tunnel and roadway operations in the event of the failure of both supplies.

The cables associated with these services should be separately routed for maximum security of supply (Section 11.6).



11.2.2. Security of Supply

Careful consideration should be given to ensure that faults on one supply cannot affect the second supply.

Two separate supplies may be prohibitively expensive. Risk assessment, in conjunction with the supply authority, should establish the interrelationship/redundancy between the two supplies where they are derived from a common HV substation.

Furthermore, failure of the supply at the HV level (e.g. by damage to overhead lines), could lead to loss of both incoming supplies and this possibility should be taken into account when assessing standby or duplicate supply requirements.

The general requirement for the electrical system design is that the electrical system including supply should be not less than 99.995% reliable with any power supply outage event to be less than one-hour duration in any one-year period. Supply should be designed for maintainability such that any individual plant room supply outage event will have a duration of less than one hour.

In the event of a total mains electricity supply failure, UPS should be provided to meet the following requirements (refer also to Section 11.5):

• essential lighting, designated signs, communications, emergency power outlets, closed circuit television, traffic and environment sensors and ancillary equipment for a minimum period of 30 minutes

• essential supply in the tunnel control building/room including tunnel management control system (TMCS) and plant management control system (PMCS) servers for a minimum period of 4 hours

• emergency lighting and exit signs in tunnel and egress routes illuminated for a minimum of 90 minutes.

All variable message signs (VMS) external to the tunnel and vehicle over-height detection devices associated with the tunnel’s safety will also require a back-up system but this is not necessarily part of the tunnel essential services supply. AS 4852.1: 2009 describes the back-up requirements for such VMSs.

Standby generators may or may not be used in conjunction with the UPS. A whole-of-life costing approach to the provision of standby power is valuable to balance the high costs of installing and maintaining full UPS systems against those of partial UPS with standby generator plant.

11.2.3. Design and Maintenance

The following requirements for electrical installation should be met:

Conduit, cubicles, trunking, cable tray boxes, metal work and cabling must be designed to withstand a tunnel environment, and should be fire resistant, non-flammable, low smoke, halogen free and corrosion resistant. Certain cable support systems are required to be fire resistant depending on the service provided.

Exposed conduits that are not in a fire rated enclosure and all cables must be low smoke halogen free. Conduit and other wire way materials within the tunnel envelope must meet the fire safety requirements for tunnels.

All electrical equipment and cabling must be installed in accordance with the relevant standards and codes, and must address safety, segregation, adequate rating for maximum demands, voltage drop limitations, durability and operational safety.

The electrical installation design must ensure continuity of supply, safe working conditions, performance, proper operating sequences and physical measures to combat a hostile environment. The design of the electrical system should take into account the whole life-cycle from installation to decommissioning including refurbishment (e.g. provisions for removal and replacement of the major components at the end of useful life). The system should be capable of being safely maintained while minimising impacts to the tunnel operations.



All plant, equipment, fittings and any other component of the permanent installation within the tunnel and other areas affected by the tunnel environment should be protected to the International Electrotechnical Commission (IEC) Category IP65.

The automatic changeover equipment must have its own independent back-up supply to enable changeover during mains power failure.

11.2.4. Electromagnetic Fields Minimisation

Electrical interference arising from electromagnetic fields caused by design and operation of any temporary and all permanent electrical supply and distribution systems for all tunnel services equipment should be controlled by selection of appropriate equipment complying with electromagnetic compatibility (EMC) standards.

11.3. High Voltage System

The high voltage distribution system should incorporate:

• dual HV supplies to all distribution transformers in conjunction with automatic load transfer on the low voltage

• independently routed cables, with routes to be geographically separated where possible to prevent a single point of failure (Section 11.6)

• encapsulated dry-type transformers where located underground

• equipment selections to suit the relevant electricity supply authority’s fault level requirements. Transformers should be continuously rated for 120% of design load.

11.4. Low Voltage System

The low voltage distribution system should include as a minimum:

• equipment selection to suit HV distribution system fault level requirements

• automatic changeover of the two incoming supplies at the main LV switchboards

• facilities to enable the automatic transfer of loads between substation transformers

• main switchboards constructed to minimum Form 3B separation as defined by AS/NZS 3439.1: 2002

• distribution boards constructed to minimum Form 2 separation as defined by AS/NZS 3439.1: 2002

• dustproof and vermin proof switchgear cubicles constructed to minimum IP65 in tunnels and minimum IP41 in switch rooms.

11.4.1. Protection Systems

System protection and monitoring should include:

• monitoring through the plant management and control system (PMCS)

• Type 2 coordinated protection grading from HV to field devices in accordance with AS/NZS 3947.4.3: 2000.



11.5. Uninterruptible Power Supply

11.5.1. General

To support required emergency response such as tunnel evacuation, an uninterruptible power supply (UPS) with appropriate autonomy must maintain power to essential operational and safety systems in the event of a mains electrical supply failure.

The tunnel characteristics and/or operating philosophy may require/allow additional loads supported by the UPS.

A standby generator may also be provided to augment the UPS.

11.5.2. Essential Loads Network

The electrical design report should list and quantify the essential loads and load shedding schedule. The essential loads should be permanently connected to the UPS equipment so that in the event of a mains failure their supply is maintained. Components of the essential load include:

• tunnel mains failure lighting in compliance with AS/NZS 1158.5: 2007

• control room lighting (to allow continued operation)

• operations management and control system (OMCS)

• CCTV and other designated traffic monitoring systems

• communications network switching and management equipment

• egress lighting (other than emergency lighting compliant with AS 2293: Set-2005)

• radio and public address (PA) systems

• fire brigade power tool sockets (if required by the fire brigade)

• other relevant components specific to the tunnel under consideration

• equipment which cannot tolerate any interruption during switching operations or while any standby generator is starting up.

It is essential that some level of lighting is maintained throughout the whole of the initial period of supply failure (Section 10.5.1).

11.5.3. Types of UPS

Static-type systems with a no-break reversion to the mains supply on failure are adequate for tunnel applications using appropriate battery capacity. Rotary types may be considered.

11.5.4. UPS Design Parameters

Each UPS system design should take account of the following factors:

• the type of load to be fed and the characteristics of the load

• acceptable limits of harmonics fed back into the power supply network, particularly where a standby generator is installed

• compatibility with standby generator plant, where provided

• the minimum period of time the UPS is required to operate under full load after mains supply failure (Section 11.2.2)



• operational and physical compatibility with other electrical equipment

• recharging times after discharge – batteries should be capable of being fully recharged, from the discharge state, in seven hours, automatically

• a battery monitoring system for automatic detection and reporting to OMCS of any individual failing batteries

• control equipment to be provided

• a maintenance bypass facility to enable maintenance (replacement of batteries) online.

11.5.5. Back-up Generating Equipment

Where it is likely that drainage pumps or ventilation plant will need to be operated under mains failure conditions to maintain the security of the tunnel systems and structure, such loads may be beyond the capacity of a UPS. For such cases, automatic start, back-up generating equipment should be considered.

Separate accommodation, with a 4-hour fire protected enclosure, should be provided for the back-up generating equipment, fuel tanks and associated equipment.

The back-up generating equipment should provide adequate power, including start-up requirements, for the essential loads supplied by the UPS. Additional loads may be connected in accordance with the fire engineering brief, such as:

• pumping system loads including fire main pressure pumps

• essential ventilation plant

• lighting and heating, ventilation and air conditioning (HVAC) equipment in services buildings

• limited tunnel lighting according to the design requirements.

Separate accommodation for the back-up generating equipment is required, with appropriate connection to control systems to ensure automatic start-up of the generators when required. A 12-hour fuel supply should be provided for the back-up equipment.

11.6. Cabling

Cabling should be designed in accordance with the latest edition of AS/NZS 3000: 2007. Cabling is usually an in-buried conduit nest in Australia although one or two tunnels use alternative configurations of similar degree of fire isolation. Cables directly exposed to the tunnel environment must be fire resistant, non-flammable, low smoke and halogen free.

It is essential that in twin bore tunnels, the HV cabling reticulation provides for the A and B supplies to be located in separate tubes. Similarly, the redundant LV reticulation and dual redundant fibre network should be separated in the two tubes.

Cables feeding services in the tunnel should be run, so far as is possible, in the verge ducts on either side of the bore. Preference should be given to lighting sub-mains being run in the verge duct adjacent to the left-hand carriageway side. Where ventilation using jet fans is employed, cables feeding these fans should be located in the verge opposite to that containing the lighting cables.

Communication cables should not be installed within 0.5 m of electricity supply cables, other than those supply cables associated solely with the communications system.

The maintenance requirements of the cables should be considered in deciding their location and preference should be given to a location that does not require the tunnel to be closed for that maintenance.



12. Design for Monitoring and Control

12.1. Operations Management and Control Systems

12.1.1. Introduction

Tunnels are usually important links in road networks and the monitoring and control of tunnel approach roads must be coordinated with the operations management and control of the tunnel. In this regard the Guide to Traffic Management Part 9: Traffic Operations (Austroads 2019a) provides relevant guidance on systems and procedures for network monitoring, maintaining serviceability and traffic control.

Tunnels will vary in their needs for management and control systems depending on the location, size and significance of the tunnel. Major urban tunnels carrying significant volumes of traffic require careful management and will need extensive and comprehensive operations management and control systems (OMCS). This includes the continuous monitoring of the tunnel operation from the tunnel control centre. However, rural tunnels, low traffic volume tunnels, short tunnels, long underpasses and some highly regulated tunnels carrying high volumes of traffic may not require extensive management and control systems.

Each tunnel should be assessed in the planning stage for the level of operational monitoring and control that is required to provide an appropriate level of safety and operational efficiency for the operation of that tunnel in an economical way. This should be undertaken using a risk management approach. AS 61508.1: 1999 describes a comprehensive, risk-based design process.

An OMCS will be required to ensure the effective management of major tunnel operations. The OMCS should:

• facilitate the effective management of incidents in the tunnel and on the approach roadways through the integrated management of the whole facility control, monitoring and communication systems

• optimise the traffic flow

• monitor and control traffic systems and traffic movements in the tunnel and on the approach roadways including any ramps (an automatic video incident detection system should be considered)

• provide accurate and timely driver information about traffic conditions and incident situations

• monitor and control tunnel plant, equipment and communication systems

• provide a high level of automation

• provide the timely presentation of relevant information to the operators at the control centre

• provide support to the operators via a real-time expert system

• include:

– a traffic management and control system (TMCS)

– a plant management and control system (PMCS)

– both supported by the tunnel network communication system (TNCS).

To facilitate effective and efficient automatic operations of detectors and monitoring systems connected via the TNCS, the OMCS may be supported by a range of additional and separate systems enabling communication between the drivers, operators and emergency services personnel such as an operation and maintenance telephone system for tunnel control staff, fire control co-ordination telephone system and public announcement/address (PA) and break-in facility in the radio re-broadcast (RRB) system.



12.1.2. Operator Interface

The interface of the OMCS with the operators should:

• be integrated into a map-based graphical user interface (GUI)

• provide all alarms in real time

• display the current status of all devices to allow an operator to assess all displays to motorists

• provide automatic operation together with manual over-ride facilities for each system and system element

• allow monitoring and control of a single system or multiple systems through operator selection

• provide all alarms and warnings in a clearly visible pop-up window classified by type (e.g. traffic incident alerts, fire, plant, maintenance, environmental factors such as CO, NOx) and severity and in a consolidated log (all alarms must be visible and selected alarms audible)

• include response procedures to assist operators with the management of all devices.

12.1.3. Response Procedures

A comprehensive set of response procedures should be developed for the management of incidents and events and for user training.

The response procedures should be automatically displayed for the relevant alarm or warning, if appropriate.

12.1.4. Trainer and Back-up System

An OMCS trainer/back-up system should:

• provide for training functions

• act as a back-up OMCS in the event of a failure of the primary OMCS

• be maintained in an operational state at all times and able to function in OMCS back-up mode within three minutes of any failure of the primary OMCS

• be capable of simulating all incident and operations managed by the system

• provide a user interface identical to the primary OMCS

• provide an environment where modifications to the OMCS can be developed and tested

• when operating in trainer mode, be easily distinguished from the on-line system.

The same set of servers may act as both a trainer and back-up system. However, if the back-up is achieved through a remote OMCS disaster recovery system/site, the (remote) training capability should be removed from the operations area.

12.1.5. Report and Logging Requirements

All significant events occurring on the facility should be logged in an OMCS event log file. The event log file must provide a record sufficient for audit purposes and the review of event sequences.

Event log files should be organised on a day boundary. Event logs for the previous day should be incorporated into an historic log area with access services available for the review of all historic log file data and retrieval for a minimum preceding period as required by the relevant road agency.

The OMCS should provide comprehensive reporting facilities including full search functionality for the management review of all activity on the OMCS.

The OMCS should have the capability to generate reports on all stored data for any selectable time interval.



12.1.6. Reliability and Availability

All components of the OMCS computer system should be duplicated for redundancy unless specifically exempted for the particular project. Some components may be impractical to duplicate (e.g. video switcher) and a decision on the duplication required should be based on the outcome of the design process for a redundant configuration to achieve the specified availability figure.

The OMCS software architecture should be designed to minimise the risk of cascading failures as the result of a fault in one software module or task.

The failure of any component or software module of the traffic monitoring control system (TMCS), plant monitoring control system (PMCS) or tunnel network communications system (TNCS) should not cause the failure of any other component or software module of the OMCS. For example, the PMCS and TMCS should be able to operate independently in case of failure of the other.

The availability of all OMCS functions should be appropriate to the design requirements, and in any case, greater than 99.995% where availability is defined as (Equation 1):

(MTBF-MTTR)/MTBF 1

where

MTBF = mean time between failures

MTTR = mean time to repair.

The MTTR should be less than three hours.

12.1.7. Performance Requirements

The OMCS should, as a minimum, satisfy the performance requirements included in Table 12.1.

Table 12.1: Performance requirements

Action Time requirement

The period between the FCC operator’s request for a display and the completion of the display build < 1.0 sec

The period between the change of state of an alarm circuit at any location and the consequent display of the alarm at the FCC

< 1.0 sec

The period between the FCC operator’s command and the consequent change of state of the selected output at the roadside controller or other remote device

< 1.0 sec

The period between an analogue change in state of a roadside controller or other remote device and the display of the changed status in the FCC

< 1.0 sec

The period between a change in an analogue input signal where it deviates outside the low and high alarm limits at a roadside controller or other remote device and the consequent display of the alarm at the FCC

< 0.5 sec

Source: EastLink Project Documents – Victoria.



12.1.8. Scope for Future Development of the OMCS

The OMCS design and configuration should be scalable to meet future and short-term demand for additional functionality, scope and dimensions of OMCS functions.

12.2. Tunnel Control Centre

The functional requirements described in Section 2.1 can be met with the provision of a tunnel control centre where appropriate. The design of the control centre will need to provide for these functions in an efficient and effective way.

The most comprehensive and integrated configuration for a tunnel control centre would include:

• An operations room where trained staff monitor and control as required using various systems such as electronic signage, public address or radio re-broadcast systems. The operators should also dispatch breakdown vehicles to help remove vehicles that have stopped in the tunnel or on adjacent roads. There should also be interlinking and liaison with other relevant road and transport agencies.

• Facilities and staff to monitor tunnel plant and equipment so that it continues to operate reliably as required under all traffic and emergency conditions. This should include scheduling and management of maintenance and repairs.

• Special incident response facilities available to the police, fire services, ambulance and other emergency services.

• Support staff and management.

• Integration with related facilities operating other parts of the road network.

A tunnel control centre such as this would incorporate:

• an operations (traffic and plant) monitoring and control room/facility

• a dedicated incident control room

• a tolling management system if required (this could be on or off site)

• associated ICT facilities including dedicated, secure computer server room(s) distinct from other building facilities

• general offices

• amenities

• workshops

• a dedicated incidents control room

• parking and marshalling areas for staff, maintenance and emergency vehicles.

Facilities such as marshalling areas for breakdown and emergency vehicles as well as supplementary incident control rooms plus associated radio and phone communication systems may also be required at locations such as the other tunnel portals and emergency egress locations to provide the requisite level of redundancy.

A wide range of tunnel control centre functions can be remote from the tunnel itself in separate and/or dedicated facilities. For example, a single control centre could monitor and control a number of tunnels and other road systems, although marshalling and incident response facilities would still be required adjacent to the tunnel itself.



The final configuration of a tunnel control centre and how a network of tunnels and individual tunnel systems is managed will depend upon:

• what facilities are currently available or could be expanded

• the timing of tunnel construction

• contractual arrangements

• operator preferences

• coordination arrangements between the authorities controlling different tunnels.

12.3. Traffic Monitoring and Control System

12.3.1. General

The efficient and safe operation of a tunnel will depend on suitable traffic monitoring and control systems. This includes CCTV and other roadside intelligent transport systems (ITS) such as lane control, speed limit, directional information, traveller information, emergency information. A traffic monitoring and control system (TMCS) should be provided in the tunnels and on adjacent roadways so that traffic flow into, through and out of the tunnels can be optimised in a safe, consistent and coordinated manner. These systems should be designed following the specific risk assessment and typically have high levels of redundancy built in. Equipment and functionality should be distributed along the tunnel and impervious to control room incidents to minimise single points of failure. Wherever practicable, provisions for redundancy should be installed in separate locations to achieve the need for continuing operation from the disaster recovery site.

Equipment forming part of the TMCS should be designed and mounted in accordance with Freeway Design Parameters for Fully Managed Operations (Austroads 2009b).

Further guidance on managed motorways/freeways may be obtained from VicRoads (2013, 2014a, 2014b and 2014c).

12.3.2. Tunnel Information Signs System

The tunnel information signs system should be designed to display short messages to motorists advising of emergencies, on-road incidents, lane closures or other relevant information. Typically these are short, single-line dot-matrix variable message signs (VMS) and/or predefined changeable message signs (CMS). The system should incorporate the ability to automatically default to blank and/or display a set message when a major system failure occurs.

Each tunnel information sign should be:

• mounted above the carriageway such that it is clearly visible from the lane to which the sign applies

• positioned at approximately 120 m intervals along the tunnel to ensure that drivers of stopped vehicles can read the sign

• capable of being individually addressed

• capable of displaying operator formed or pre-programmed messages.



12.3.3. Lane Control System

A lane use signal (LUS) or lane control sign (LCS) system sometimes combined with a variable speed limit (VSL) system may be implemented for the tunnel, on the approaches to the tunnel and at other locations where it is regularly required to indicate to motorists whether or not a traffic lane is open and the appropriate speed limit.

These in turn may be interlinked with the tunnel information signs system and/or VMS system to provide supporting traveller information. The traffic management plan should be aligned with the corresponding CCTV cameras.

The lane control system may also be required for temporary lane closures in the tunnel for maintenance activities or to control traffic during incidents that may occur. In addition, where it is necessary to use a one-way tunnel as a two-way road during maintenance or incidents, the lane control system will be required to guide traffic safely in both directions. In this case with contra- flow traffic provisions the double sided/faced LUS/LCS should be provided.

The lane control system should incorporate as a minimum:

• centralised control of each sign from the control centre

• detection of sign failures

• lane use conflict control logic

• confirmation of the correct lane control settings at all times to the control centre

• failure to set as expected alerts to the control centre.

The status of the lane control system should be clearly displayed in real time on a traffic operations display at the control centre.

Each sign should be positioned such that as a minimum, drivers are able to read one downstream signal for their respective lane at all times. Where appropriate, the sign should also comply with Best Practice for Variable Speed Limits: Best Practice Recommendations (Austroads 2009a).

Consideration should be given to the maintenance implications when locating the signs and make adjustments where possible to ensure that maintenance functions can be performed safely with minimal traffic disruption.

12.3.4. Variable Speed Limit (VSL) System

The VSL system should as a minimum:

• comprise the VSL and a computer control system to control and monitor all variable speed limits and log the status of the variable speed limit at any time

• be integrated with the lane control system

• be designed to interface with any permanent speed cameras installed on the system.

VSL signs should:

• be capable of displaying the posted speed in variable increments

• comply with Austroads (2009a)

• be in accordance with the relevant jurisdictional legislation and policy and able to flash inner rings of the red annulus and/or conspicuity devices as specified

• apply to all lanes open for traffic at that point.

The status of the VSL system should be clearly displayed in real time on a traffic operations display at the control centre.



12.3.5. Ramp Control Signs System

A ramp control signs system may be required to inform motorists when access to or egress from the tunnel or the approach road has been closed (see Section 12.3.7 regarding managing ramp closures in combination with traffic diversion management plans).

The ramp control signs system should consist of a primary and secondary sign on each side-road connection to the approach road and the tunnel.

12.3.6. Variable Message Signing System

A variable message signing system will be required on the approach roads to most tunnel systems. Variable message signs (VMS) should be located to meet the requirements of the traffic control and monitoring system and relevant traffic diversion management plans. The tunnel and neighbouring road network operators should consider developing operational processes to deliver co-ordinated incident response messages to road users.

Consideration should be given to managing ramp closures and traffic diversion management plans as one system, using a combination of both VMS and other traffic management subsystems and devices, such as ramp control signs, VSLS, LUS and moveable barriers. VMS must be located prior to major decision/diversion points on tunnel approaches.

The system should be capable of displaying pre-determined and operator entered messages from the tunnel control centre, and report real-time status and fault data to the tunnel control centre about each VMS.

VMS should be:

• mounted adjacent to or above a carriageway such that they are clearly visible to drivers from each lane to which each sign applies

• designed to provide legible, changeable, alpha-numeric and graphic information relating to the operation of the tunnel.

VMS should be located to meet the requirements of the traffic control and monitoring system and relevant traffic diversion management plans.

Consideration should be given to managing ramp closures and traffic diversion management plans as one system, using a combination of both VMS and ramp control signs. Signage must be located prior to major decision/diversion points on tunnel approaches.

Traveller information may be displayed on these signs and may be considered in order to provide motorists with destination information, estimated travel times and congestion levels on the approach roads to the tunnel and in the tunnel itself.

12.3.7. Tunnel Closures

A tunnel closure system is required to allow (or enable) the tunnel to be closed to traffic.

In addition, the approaching traffic must be warned of the traffic stopped ahead and provided with advice of an alternative route (or routes) where available. VMS (or changeable message signs) should be placed 1 km and 0.5 km before the tunnel closure indicators and prior to the diversion route where one is available. A VMS is also required at or close to the tunnel portal in a position able to be read by approaching traffic.



Tunnel closure indicators (typically flashing red stop signals) may be located at one or more of three alternative places, namely:

• in front of the tunnel portal

• in turning points in the tunnel

• immediately downstream of the place defined as a diversion route prior to the tunnel.

In certain circumstances it can be appropriate to erect signals at all of these alternative places (Section 12.3.9).

The tunnel closure system may be activated:

• by a remote control from a traffic control centre (where a tunnel has a dedicated 24-hour traffic control centre monitoring the tunnel and its operations, the tunnel closure indicators should not be automatically activated)

• locally through control panels on the equipment.

Figure 12.1 illustrates an example of a tunnel closure on the approach to a portal utilising boom gates, signs and a turn-around facility in the median. This treatment should also be supplemented by appropriate traffic management measures upstream of the closure designed to efficiently divert traffic from the motorway.

The tunnel closure system should be linked to the local traffic control system to prevent phases being called up on the local connecting roads that would otherwise feed the tunnel. Where an approach to the tunnel is controlled by a signalised intersection, the tunnel closure system should prevent such phases being called. Additional signage should be located at and before the intersection and activated automatically upon tunnel closure. The approach road to the tunnel is not part of this system.



Figure 12.1: An example of a tunnel closure treatment utilising boom gates, signals and signs

Notes:

The turn-around facility is usually located relatively close to the tunnel portal (e.g. within 200 m). Where practicable a dedicated emergency exit ramp may be provided in advance of this treatment.

In the event of a closure, the motorway management system or additional traffic management measures should be activated upstream of the tunnel closure to direct traffic to exit the motorway via normal exit ramps.

Source: Based on Department of Main Roads (2008).



12.3.8. Remotely Controlled Barriers

Physical barriers can give a clear indication of the operational status of the tunnel and/or approach ramps. The need for physical barriers at locations remote from the tunnel (e.g. on approach ramps or roadways) should be considered on the basis of expected frequency of use. However, they should be provided at all tunnel portals as close as reasonably practical to the portal considering the specific operational requirements of the tunnel, to physically prevent tunnel entry in the event of a fire and life safety event.

The need for remote-controlled barriers should be evaluated as part of the automatic traffic control system (for example CCTV surveillance) for traffic redirection, or to undertake certain critical measures with regard to safety. Also, experience shows that open, manually-operated barriers can conflict with operation of the tunnel closure indicators, and thereby confuse the operational status of the tunnel. Therefore only remote-controlled physical barriers should be used in combination with tunnel closure indicators. However, remote-controlled barriers should also be able to be operated manually at the site.

The barrier and VMS should be co-located with overhead LCS or LUS to reinforce tunnel closures and the aspects on the overhead gantry would appear as shown in Figure 12.2. Flashing red conspicuity lanterns on the barrier should be considered for this application, similar to railway boom gates.

Figure 12.2: Tunnel closures – signal aspects

The barrier should be long enough to clearly indicate that the entry lane is blocked but designed such that it is possible for emergency vehicles to access the tunnel.

Remote-controlled barriers may be of the raise/lower type or as horizontal swinging barriers. Consideration should be given to the speed impact threshold at which the barriers should bend/ collapse.

When remote-controlled barriers are used they should be equipped with a control function to ensure that vehicles are not situated under the barrier when it is lowered, and that the operator is always aware of the position of the barrier. This should be visually verified by an operator.

The remote-controlled barrier should not be able to be operated automatically unless sufficient advance warning has been given by the red stop signals linked to the barrier. If there is a malfunction with the OMCS, and warning lights are not available, then the barrier needs to be able to be operated manually, regardless of lights/signs.

12.3.9. Traffic Monitoring

Automatic traffic monitoring, vehicle detection and counting

A system for the collection of real-time traffic data, in a suitable form, should be provided. The data required will usually include:

• speed of vehicles – the average speed of the vehicles in each lane during the collection period in km/h in the traffic monitoring time interval

• volume of vehicles – the total number of vehicles in each lane in the traffic monitoring time interval

• occupancy of lanes – the amount of time each lane is occupied at the collection point during the traffic monitoring time interval as a percentage of the total time.

Data collection stations should also be placed at all entry and exit ramps, intersections, merges and diverges, and strategically located within the tunnel proper.



Vehicle measuring

It may also be beneficial to provide a vehicle detection system to monitor the various classes of vehicle using the facility. A suitable system would:

• classify vehicles on all lanes on each carriageway

• be continuously operational (except for maintenance purposes)

• be located where the longitudinal grade is less than 1% and crossfall is less than 3%

• meet the technical requirements

• classify all vehicles to the 12 vehicle classes identified in the Guide to Traffic Management Part 3: Traffic Studies and Analysis (Austroads 2017b).

Over-height vehicle detection and control

Over-height vehicle detection systems should be located prior to and after the last exit/diversion point for over-height vehicles. The detection point prior to the last exit/diversion point will provide proactive notification to the driver to divert and alert the tunnel operator of the approaching vehicle. The detection point after that exit will confirm for the tunnel operator that the over-height vehicle has not diverted and is tunnel bound, prompting immediate closure of the tunnel (Section 12.3.8).

Arrangements for the vehicle to exit the portal approach area should be provided for those vehicles that proceed to that point. Parking areas may also be required to store such vehicles temporarily.

Dangerous goods vehicle control

Where it is necessary to divert vehicles carrying dangerous goods (placarded vehicles), appropriate signage will be required at locations where it is desired to divert the vehicle to another route as well as at the portal to prevent the vehicle from entering the tunnel.

Arrangements for the vehicle to exit the portal area should be provided for those vehicles that proceed to that point. Parking areas may also be required to store such vehicles temporarily.

12.3.10. Closed Circuit Television

Closed circuit television (CCTV) surveillance is generally applicable to tunnels with a high-capacity usage throughout much of the day, such that those incidents requiring traffic regulation measures, and where queues and other possible incidents arise, may be immediately and efficiently recognised.

Remote tunnels some distance from any emergency services also benefit from the use of CCTV as operators can use the CCTVs to verify an incident call or automatic alarm before implementing response procedures. CCTVs are commonly used as the technology is so readily available, even for remote sites.

CCTV surveillance therefore necessitates links to a traffic/tunnel control centre. Consideration should be given to the requirements for recording CCTV images and management of recorded images.

Local CCTV surveillance is required to verify operation of remote-controlled barriers (Section 12.3.8), stopped traffic (even before any incident occurs), broken-down vehicles (before the vehicle owner calls in on an emergency phone), wayward pedestrians or animals, and operation of emergency equipment.

The CCTV system should continuously view all road and road-related areas within the tunnel, entry and exit ramps and associated approaches and departures. It should also allow visual confirmation of sign displays and other traffic management indicators. When used for incident detection, line of sight visibility is required to all areas to be viewed.



CCTV within the tunnel should be spaced at intervals that provide clear and legible viewing of all tunnel traffic lanes to facilitate the timely identification of incidents, breakdowns, accidents and the operation of the deluge system. Spacing will be affected by the tunnel horizontal and vertical curvature and the mounting height, location and type of equipment, resulting in a spacing of 30 to 150 m when incident detection is required. If monitoring only is required (typically for remote and/or minor tunnels), then spacing up to 200 m may be appropriate depending on the geometry and cross-section of the tunnel.

CCTV should be a mixture of fixed and PTZ cameras, fixed cameras at 60 m intervals, supplemented by PTZ cameras. The direction of the fixed cameras will depend on the systems to be used. The aims of TV systems are to:

• allow 100% of the tunnel to be viewed at all times

• site the CCTV such that the operator and video recordings capture the cause and results of incidents for the purposes of debriefing and training

• allow the accurate deployment of deluge and therefore there should be at least one CCTV camera for two deluge zones of 30 m each.

12.3.11. Automatic Incident Detection

The traffic monitoring systems and queue detection algorithms may be used to provide automatic detection of traffic incidents. As well as detecting incidents, they can be used to automatically reduce speeds for traffic queues to prevent secondary accidents.

CCTV may be used for both incident detection and incident verification. The cameras can be connected to the automatic incident detection (AID) system to allow operators to locate the incident and provide vision of it after being alerted. Operators can also rapidly verify incidents, changes in traffic flow and dangerous or abnormal road conditions. Accordingly, the design should provide the necessary interfaces with the traffic control system where appropriate.

Video processing hardware and software to detect incidents should be provided and interfaced with computers located in the control centre. Video software algorithms are currently available to detect issues in tunnels such as stopped vehicles, congestion and changes in the direction of vehicle travel, pedestrians and dropped objects/debris. Video AID systems also provide some traffic information (speed and volumes) during off-peak or low traffic volume conditions and may provide smoke detection based on visibility within the tunnel, and fire detection based on thermal imaging (refer to PIARC 2004).

In major tunnels, the AID system should be designed as an integral part of the control systems. The elements of the whole system are included in the individual components described in this section and the sections on fire and life safety, electrical, ventilation and lighting. These must be designed as an integrated system to provide the level of incident detection and communications links and interfaces between the communication system elements, as required (Section 12.5).

12.4. Directional Signing System

Desirably, major direction signing should be accomplished outside the confines of the tunnel, but this may not be possible on longer tunnels and those associated with interchanges. Direction signs are relatively large and adequate space will have to be designed into the tunnel to accommodate them, the signs designed to fit the tunnel envelope or a combination of these approaches. The provision of traveller information should be considered for decision points which may be located a significant distance from the actual tunnel.

Design of direction signs should be in accord with AS 1742.15: 2007 in Australia, and NZ Transport Agency (2010a) in New Zealand. For signs inside tunnels, specific designs will be required to ensure that the reduced sign size available is sufficiently visible to allow drivers to take the necessary decisions sufficiently in advance of the actions required.

All static road signs within tunnels may be internally lit where appropriate.



12.5. Communications System

12.5.1. General

To provide appropriate levels of safety over the full range of operating conditions, facilities for traffic management and tunnel communication should be fully integrated with the operation of systems installed to monitor and control the tunnel environment. Tunnel systems should interface with the communication and signalling systems used on the adjoining freeway/motorway or other major road networks, at the level appropriate to the location and size of the tunnel. System interfaces should utilise an open, industry standard.

In rural and minor tunnels where only basic monitoring and control systems are used, communication will generally be limited to the emergency telephone system. The full range of services will only be required in major, highly trafficked urban road tunnels. The level of communication systems required for a specific project should be determined in the planning of the tunnel.

Where installed, the communication system should allow the tunnel operators to communicate with tunnel users. Automated systems must be capable of being manually operated.

The communication system may include:

• a tunnel radio re-broadcast system with the break-in facility

• a tunnel public address system compatible with the radio re-broadcast system

• a tunnel mobile telephone coverage system

• a help or motorist emergency telephone system (METS)

• other communication systems including an operation and maintenance telephone system, and fire control co-ordination telephone system

• radio communication system coverage including emergency services, police, ambulance, government radio network

• static GPS beacons.

12.5.2. Radio Re-broadcast

The radio re-broadcast (RRB) system should re-broadcast in seamless operation and at no cost to the radio broadcasters agreed by the road agency for the area where the tunnel is located. Typically only the most popular stations will be re-broadcast.

Where installed, the radio re-broadcast system should:

• Provide sufficient signal strength on the re-broadcast stations to ensure that all users within the tunnel (including equipment rooms, emergency exit areas and cross-passages) are capable of receiving re-broadcasts.

• Enable the tunnel operator locally or remotely to temporarily interrupt all live radio channels in the tunnel to transmit live or pre-recorded messages.

• Be configured so that each tunnel tube can be separately interrupted. The RRB should be segmented such that different sections/carriageways can receive messages specific to them (i.e. for each direction and cross-passages).

• Allow for the re-broadcast of digital radio stations.

The RRB break-in facility is regarded as part of the safety and emergency evacuation system of the tunnel and can only be used in response to incidents that have occurred and that relate to the operation of the tunnel. Where RRB is installed, consideration should also be given to re-broadcasting traffic data used by GPS navigation devices.



12.5.3. Emergency Services Communications

Methods of maintaining emergency services communications within the tunnel should be discussed with the relevant authorities.

12.5.4. Public Address System

The public address system should be able to be used in conjunction with the radio re-broadcast system.

The tunnel public address system should be audible in all areas throughout the tunnel environment under all traffic operating conditions (refer to Section 9.4). It should also be capable of addressing specific areas of the tunnel and the-cross passages.

Because of the acoustic properties of the tunnel, specialist advice will be required in the design of the tunnel interior and the system to achieve an acceptable quality of sound from the system. A simple message to turn radios on to hear more detailed messages would give a good combination of public address system and radio.

12.5.5. Help Phones/Motorist Emergency Telephone System

Help phones (METS) are to be provided in tunnels to allow motorists to contact the relevant control centre or other help location. They should be located according to the relevant authority requirements (typically 60 m intervals), and may be adjacent to (or in) the emergency cabinets.

These telephones may not be required in short tunnels where the approach road system provides an adequate service. A telephone will be required in the tunnel if there is no other help phone available within 200 m of each tunnel portal.

The help phone system should interface with the CCTV system to automatically display live images of the respective phone to the operator who answers the call.

Reference should also be made to the Guide to Road Design Part 6B: Roadside Environment (Austroads 2015b) for details of help telephone requirements.

12.5.6. Mobile Telephones Re-broadcast

Designers should provide for a tunnel mobile telephone system and provide continuity of service for all mobile phone carriers where terrestrial mobile telephone coverage is available.

12.6. Plant Management and Control System

A plant management and control system (PMCS) should be designed as part of the OMCS. The PMCS integrates monitoring and control of all mechanical and electrical plant associated with the safe and efficient operation and maintenance of the tunnel and approach roadways as appropriate. The PMCS should interface with the TMCS as necessary to coordinate traffic and plant management in response to incidents in both systems. For example, the ‘CO exposure over travel time alerts’ must be based on algorithms and inputs from air-quality monitoring stations (PMCS) and real-time traffic monitoring data (TMCS inputs), tightly integrated to achieve this functionality.

The PMCS must be designed so that no single point of failure causes:

• major performance degradation of one or more elements

• total unavailability of operational functions, which would necessitate the closure of the tunnel.



The PMCS should be capable of showing the status, alarms and faults of all plant, equipment and other operating systems, and provide a consolidated user interface to the operator. Further details of the plant and equipment are described throughout the Guide.

The PMCS should be supported by secondary and/or manual systems (e.g. for deluge control) to allow tunnels to be safely operated in a mode involving a higher degree of operator involvement in the event of system failure.

12.7. Tunnel Network Communication System

Where installed, the OMCS should utilise a dual-ring automatic optical fibre ethernet network (with built-in redundancy) which supports network management. The internet protocol (IP) and CCTV networks should avoid cables of the redundant path being located within the same tunnel or cable containment structure.



13. Services Buildings and Plant Rooms

13.1. General

Tunnel services buildings and plant rooms house the main electricity substation and temporary tunnel control centre (if required). Additional structures may be required for substations and plant rooms at other locations adjacent to the tunnel. Plant rooms should be sized not only to accommodate the plant and associated systems to be installed initially at the tunnel, but also to provide for any foreseeable future requirements.

Building layout should facilitate effective management of operations and maintenance and fully reflect the system of tunnel management to be adopted (e.g. staffed or unstaffed tunnels). If the services buildings are normally unstaffed, they should be suitable for occasional use as a temporary control facility during maintenance and emergency operations.

In addition to the facilities required for the tunnel equipment and systems, maintenance workshops, stores, messing and toilet facilities may be required for operational, maintenance and contractors’ staff.

Access to the services buildings should be strictly controlled and access facilities managed to detect and prevent unauthorised entry and operation of plant. Adequate security arrangements should be provided to protect all materials and equipment.

As well as normal lighting, the provision of emergency lighting (for escape under mains failure conditions), full standby lighting and heating, ventilation and air conditioning (HVAC) to permit continued normal use of selected areas such as the control room if normal power fails should also be provided.

All buildings are to be designed in accordance with the relevant Australian/New Zealand Standards (e.g. International Code Council 2015) and any particular requirements of the jurisdiction in which the tunnel is being constructed.

13.2. Design and Layout

13.2.1. Space and Provision Requirements

Space and suitable cable access may be required for each of the following:

• control room

• electricity supply authority intake and metering

• HV switchgear

• transformer pens

• diesel generator, fuel tanks and dump tank

• UPS and battery equipment

• LV switchgear including control and interface panels for lighting and ventilation systems

• fire protection systems

• HVAC plant

• drainage pumping equipment and associated electrical equipment

• computer, control systems and peripherals

• radio and telephone communications equipment (possibly also a secure area for police network)

• mobile phones and related mobile communication services in tunnels by mobile telephone communication carriers

• protected mains sockets for portable tools and test equipment.



13.2.2. Cable and Equipment Separation

To minimise the risk of radiated interference, communications equipment and cables should be located as far as possible from high voltage and low voltage switchgear, cabling and generator plant.

13.2.3. Future Maintenance

Dirt and grime cause major maintenance problems for control panels and technical equipment in tunnel services buildings and plant rooms in tunnels. The design of the services buildings should be such as to avoid the ingress of tunnel air into these locations.

13.3. Heating, Ventilation and Air Conditioning

The room where the control panel is situated and other rooms with technical equipment should have an operating temperature related to the requirements of the installed equipment. Air conditioning may be required to maintain the temperature at acceptable levels and an automatic warning system should be installed to warn of any failure of the air conditioning plant.

A ventilation system will be required to prevent any dangerous build-up of gas that may be emitted from batteries.

13.4. Floor Loading

The structural design should consider the need for a false floor to allow cabling to be located under the floor which should be designed to accommodate the expected loading caused by the equipment being installed.

Cables must not be run beneath the floor in battery rooms. Floors in battery rooms must be of solid construction and finished with a dust and alkali resistant surface. These floors should have drainage outlets to allow for electrolyte and cleaning water removal to an appropriate treatment and disposal area.

13.5. Lightning Protection

An assessment of the need for lightning protection should be carried out using a risk management approach in accordance with AS/NZS 1768: 2007.

13.6. Building Security and Fire Protection

13.6.1. Intruder Alarm System

An intruder alarm system should be installed and connected to the control centre. An external self-contained alarm bell with its own battery unit should also be provided.

13.6.2. Fire Alarm and Extinguishing Systems

A fire alarm and automatic fire extinguishing system should be provided in the service buildings to a standard satisfactory to the relevant fire authority in the jurisdiction concerned.



14. Construction Issues

14.1. Overview

In the planning process for tunnels, the potential construction methods to be used should be considered to ensure that the design proposed would be able to be constructed economically and safely. The design of the tunnel should be undertaken with full knowledge of the construction methods to be used and the form of project delivery.

All construction activity has to be undertaken in accordance with relevant legislation and in some jurisdictions, a specific code of practice for tunnels (e.g. WorkCover NSW 2006; Workplace Health and Safety Queensland 2011). The design must take account of the requirements of any such codes and ensure that the tunnel is able to be constructed in accordance with those requirements.

Tunnelling, separate to mining, is an industry with high risks that need to be managed (note that tunnel construction in NZ is covered by mining regulations whilst the tunnel is being excavated).

The codes of practice provide practical guidance to safe tunnel construction and apply to the construction of underground tunnels, shafts and passageways. They also apply to cut-and-cover excavations, both those physically connected to ongoing underground construction tunnels and those cut-and-cover operations that create conditions characteristic of underground construction.

The purpose of the codes is to provide a health and safety framework, including technical criteria and guidance, to help plan the tunnel construction. The code gives health and safety guidance with specific requirements to assist in achieving compliance with Acts of parliament, Regulations and subordinate health and safety legislation.

These requirements include:

• geological and geotechnical exploration requirements

• construction work relating to tunnels and shafts

• tunnel design considerations

• geo-mechanical analysis

• design of tunnel linings

• instrumentation and monitoring during the construction and fit-out phase of tunnel construction.

Specific tunnelling hazards that must be eliminated or minimised include:

• reduced natural ventilation and light

• difficult and limited access and egress

• exposure to airborne contaminants

• fire

• explosion.

Particular attention should be given to the risks associated with temporary works and they should be designed with the same rigour applied to the final structure. Figure 14.1 shows an example of a tunnel under construction.



Figure 14.1: Tunnel under construction (CityLink tunnel, Melbourne)

Source: Transurban.

14.2. Responsibility of Designers

Designers should ensure that:

• to the extent that they have control over a particular section of design work, the tunnel structure (or plant) can be safely erected, used, repaired, cleaned, maintained and demolished (life cycle), so that the health and safety of any person is not put at risk by the design (refer also to Section 3.1.2)

• information is provided to the client about the health and safety aspects of the design.

Designers should also ensure that hazards associated with the following are identified before commencing construction work:

• the design of the structure (permanent or temporary)

• systems of work required to erect, repair, clean and maintain the structure

• the intended use of the structure

• materials needed in the construction of the structure

• the demolition and life cycle of the structure.



Where there is more than one designer, critical aspects of the project should be documented and consultation carried out between all of the designers, to ensure the safe integration of all of the different design aspects in the work. When risks remain in the design work, information should be included with the design information to alert others to the risks.

The designer should document the assumed geotechnical conditions used in the design to enable exposed conditions to be compared against the design assumptions as the tunnelling progresses. This allows for monitoring of the conditions and a reassessment of the design, where the geotechnical conditions differ from that assumed in the design. This applies to plant likely to be affected by such a change, as well as the tunnel and associated ground support systems.

14.3. Design Review for Construction

The initial tunnel design should be reviewed before construction commences, usually by or in consultation with the designer and principal contractor, and should be amended if necessary in line with the construction needs before excavation commences.

This review should consider a range of construction issues, such as:

• the excavation method

• additional excavation for temporary access

• ventilation

• spoil removal

• refuges

• rail sidings (if required)

• loadings from roof-mounted spoil conveyors and ventilation systems.

As well as amending the tunnel design itself, the design review should produce concept designs which may include:

• ground support

• the ventilation system

• the construction electrical system

• the materials handling system.

Safe tunnel design and construction go hand-in-hand, and their suitability to the ground and environmental conditions is more safety-critical in underground work than in any other construction activity. Consequently, continuity in engineering practices at the planning, investigation, design and construction stages is considered necessary.

This can be achieved more effectively by the involvement of a single organisation throughout.

However, if the designer’s direction changes, a way should be devised to ensure that the essential continuity is maintained and that the total planning, investigation, design and construction process is not fragmented.

14.4. Ventilation System for Construction

The ventilation system should be designed to provide adequate ventilation levels throughout the tunnel during construction, including providing additional localised extraction ventilation to deal with the production of dust, heat or fumes from the excavation process, operation of large plant or other activities, such as maintenance.



The design should allow for the need to install ventilation equipment or ducting as the excavation progresses to maintain adequate air supply to the working face.

As far as possible, this system should be designed to be compatible with the final ventilation system required for the tunnel while in operation.

14.5. Design Review for Construction

The initial tunnel design should be reviewed before construction commences, usually by or in consultation with the designer and principal contractor, and should be amended if necessary in line with the construction needs before excavation commences.

This review should consider a range of construction issues, such as:

• the excavation method

• additional excavation for temporary access

• ventilation

• spoil removal

• refuges

• rail sidings (if required)

• loadings from roof-mounted spoil conveyors and ventilation systems.

As well as amending the tunnel design itself, the design review should produce concept designs which may include:

• ground support

• the ventilation system

• the construction electrical system

• the materials handling system.

Safe tunnel design and construction go hand-in-hand, and their suitability to the ground and environmental conditions is more safety-critical in underground work than in any other construction activity. Consequently, continuity in engineering practices at the planning, investigation, design and construction stages is considered necessary.

This can be achieved more effectively by the involvement of a single organisation throughout.

However, if the designer’s direction changes, a way should be devised to ensure that the essential continuity is maintained and that the total planning, investigation, design and construction process is not fragmented.

14.6. Ventilation System for Construction

The ventilation system should be designed to provide adequate ventilation levels throughout the tunnel during construction, including providing additional localised extraction ventilation to deal with the production of dust, heat or fumes from the excavation process, operation of large plant or other activities, such as maintenance.

The design should allow for the need to install ventilation equipment or ducting as the excavation progresses to maintain adequate air supply to the working face.

As far as possible, this system should be designed to be compatible with the final ventilation system required for the tunnel while in operation.



Figure 14.2: Tunnel boring machine – Clem 7 tunnel

Source: River City Motorway.

Special ground conditions in close proximity to the tunnel and other special circumstances may require separate risk analyses. The geological structure of areas adjacent to the site and for some distance from the site should be examined to determine whether any particular strata will convey the vibrations to buildings or other sensitive receptors remote from the site.

Inspection and registration of buildings should be undertaken prior to any work proceeding and must be undertaken in the presence of the owner and conducted by an independent, appropriately qualified, competent person. The description should be supplemented by photographs and/or video film.

In areas where specified limits have been determined, vibration measurements should always be undertaken. The guidelines in the Standards Norway publication NS 8141-1: 2012 and NS 8141-2: 2013 state the required specifications of the investigation equipment and how the vibration should be measured and reported. Cenek, Sutherland and McIver’s (2012) research report, Ground Vibration from Road Construction, also provides some information on tunnel construction.

The effects of ground vibration are classified into three categories – human exposure, building contents, and building structures.

Human exposure

Australian Standard AS ISO 2631.2: 2014 provides guidelines on the effect of various levels of vibration on human perceptions. These guidelines may be used when considering measures that may be required to mitigate the effect of vibrations caused by construction activities.



Continuous and shock-induced vibration in buildings has been adopted as the relevant standard for nuisance vibration levels. The standard provides a collection of curves that specify acceptable vibration levels, at each frequency, for different circumstances.

Building contents

While there is currently no Australian Standard covering ground vibration from construction sites, limiting ground vibration to no more than 5.0 mm/s at the closest sensitive structure is a common guideline used by road construction authorities and is a limit that is generally acceptable to the community and well below levels at which structural damage may occur.

Structural damage to buildings

There is no Australian Standard currently for assessment of building damage caused by vibration energy. However, the British Standard BS 7385-2: 1993 can be used as a guide to assess the likelihood of building damage from ground vibration.

BS 7385-2: 1993 suggests levels at which ‘cosmetic’, ‘minor’ and ‘major’ categories of damage might occur. Further to this, the German Standard DIN 4150-3: 1999 also provides recommended maximum levels of vibration to reduce the likelihood of building damage caused by vibration.



15. Tunnel Commissioning

15.1. General

Commissioning is a vital part of the development of the tunnel to ensure that it will function as planned and provide the operator with a robust operating system. This requires the early involvement of the operator to ensure all factors are considered. Planning of the construction and hand-over process must allow adequate time for the commissioning process and the changes and modifications that may be required as a result. Priority must be given to successfully completing the commissioning process before the tunnel is opened to traffic, notwithstanding the desire to make use of the investment as soon as possible.

Complete records of the commissioning process, testing undertaken and the results must be kept.

15.2. The Commissioning Plan


The testing and commissioning plan should be prepared prior to undertaking any testing and commissioning activities. The plan should provide a structured approach to the testing and commissioning and produce all necessary documentation to demonstrate the satisfactory performance of the tunnel systems.

The testing and commissioning plan should demonstrate that the system meets its planned design performance. In addition, a number of assumptions may have been made during the design, and the plan should test each of these assumptions. Where the results of the plan do not verify the assumptions made in the design process, the commissioning team should re-assess the performance of the design and determine if it complies with the design intent. If this is not possible, the construction and installation should be rectified.

The commissioning plan should include:

• defining the components to be tested and inspected appointing appropriately qualified and competent personnel to undertake the testing and inspection, to witness the testing and to verify the testing; operators should be part of the witness testing of equipment to provide feedback

• establishing the testing and commissioning protocols

• defining the acceptance criteria

• undertaking the testing required

• training the operating personnel in the required procedures

• undertaking corrective actions revealed by the testing process

• documenting the testing, results and actions taken

• establishing a system for continuous review and improvement of the systems.

15.2.2. Personnel

Competent and suitably qualified personnel should undertake, witness, verify and approve the testing and commissioning. Second party witnessing and third party verification should be undertaken as necessary to gain confidence in the satisfactory performance of the systems.



15.2.3. Testing and Commissioning Protocol

The protocol should:

• include the starting conditions, details of any intermediate steps, the deployed condition and, where appropriate, the recovery from the deployed condition

• include the measurements, observations and calculations required at each step and should not specify subjective measures

• define the conditions under which the tests should be carried out and the calibration and accuracy of all test equipment

• be adequately refined to obtain reproducibility and repeatability within the permitted tolerance

• address the occupational health and safety requirements of test participants and the environmental management plans that may be required.

15.2.4. Acceptance Criteria

For each test and each step of the test, the minimum performance criteria should be established with a clear and measurable pass/fail criterion defined in terms of the testing and commissioning plan and the measurements taken during the plan.

The acceptance criteria should cover the range of expected performance criteria, the tolerance and treatment of measurement uncertainty and should be specified prior to undertaking the testing and commissioning. Any non-conformances should be documented.

15.2.5. Corrective Actions

Corrective actions should be raised where a component and/or system fails part or all of the testing procedure. Upon completion of the corrective action, the component and/or system should be re-tested.

15.2.6. Documentation

Prior to undertaking any commissioning, a document should be prepared setting out the following:

• details of component/systems to be tested or commissioned

• the commissioning process

• the test and verification protocol to be applied

• the acceptance criteria

• action to be taken in case of non-conformance

• a suitable pro-forma for recording commissioning measurement and data

• name of the testing body.

15.3. Testing and Commissioning of System Components


The testing and commissioning of system components is usually undertaken using factory acceptance testing (FAT). Factory acceptance testing is the primary tool for the verification of individual components prior to site installation. Depending on the component, the extent of the FAT phase will vary. For standard off-the-shelf components the extent of FAT may be limited to sampling and type testing. The FAT for bespoke or non-standard equipment may be exhaustive.



Particular importance should be placed on the FAT phase if a component or the particular application is unusual or unique. Where reliance is placed on an unproven component or application, every effort should be made to demonstrate the successful performance early in the project cycle.

The sampling and type-testing criteria of FAT include the following:

• Sampling and type testing should be consistent with the criticality of the equipment. Full non-destructive testing may be appropriate for critical equipment.

• Less critical equipment may be subject to a sampling protocol that ensures an appropriate confidence level is obtained for the entire batch.

• Results of sample testing should demonstrate consistency with the type-approved prototype.

In addition to factory acceptance testing, a range of functionality tests will be required to be undertaken in the completed tunnel. Details of these are described in the following sections.

The results of acceptance tests should be fully documented. The documentation and reports should have the following information:

• model and description of item tested including batch and serial numbers

• test protocol

• test conditions

• results of measurements and calculations

• manufacturer’s name

• testing authority name

• date of test

• witness to the test

• any departure from the testing protocol

• statement regarding meeting the acceptance criteria or otherwise

• any pertinent observation.

15.3.2. Fire Safety System

Commissioning of the fire safety system should be in accordance with the procedures described in the Australian Standard Tunnel Fire Safety (AS 4825: 2011).

15.3.3. Ventilation System Validation

The commissioning process for the ventilation system should determine the tests required to meet the objectives described by PIARC (2007) and further developed in PIARC (2011) to ensure that the system as designed meets the required operating needs. It will not be possible to perform tests at the scale of the design fires but it may be necessary to conduct real tests at a lesser scale to ensure that the systems do respond adequately. These tests may also be used as a training medium for operators and staff.

PIARC (2007) states:

Because the ventilation system plays a major role in tunnel safety, it is essential that it operates properly and effectively at all times. To achieve this goal, sets of tests have to be defined and adapted to specific tunnel specifications.



The objectives of road tunnel ventilation system testing are to:

• verify the functionality of all elements of the system, both at the time of ordering (factory and acceptance testing) and in situ (functionality testing at specified intervals)

• verify the in situ performance of the system and its component parts by comparing it to the design specifications.

Three kinds of tests may be performed in order to check the equipment and the safety objectives of the ventilation system, namely:

• Factory acceptance tests – aimed at checking that the equipment’s actual performance matches the specified requirements using appropriate procedures, usually defined in the test guidelines.

• On-site unit tests – aimed at checking that equipment operation is in accordance with the project specifications.

• Integration tests – aimed at checking that the safety objectives match, especially with regard to smoke control. The first set of integration tests may be performed without a fire in order to quantify the ventilation capacity, and a second set of tests may involve a calibrated fire in order to account for the buoyancy effects and to visualise the smoke development.

Hall (2006) notes the following:

As it may be impracticable to test the performance of the ventilation system against severe fires in the tunnel, the performance of the ventilation system should be evaluated against a representative set of cold flow cases, which have been identified and analysed during design.

The site tests should include the:

• Functional testing of individual items of equipment

• The performance of individual items of equipment, including start-up time, the measurement of noise and vibration levels if applicable, installation effects, power consumption, etc.

• The integrated operation of systems, including the coordinated operation of individual items of equipment and their interlocks

• The performance of the system, operating in each of its design modes or configurations, including noise measurements etc. as for as the individual items of equipment.

• Air velocity measurements should be taken at appropriate locations along the tunnel, depending on the configuration of the tunnel in question. At each location along the tunnel, measurements should be taken at a suitable number of points in the cross section, for example, in accordance with ISO 5802 ‘Fans for general purpose – performance testing in situ’, in order to determine the bulk mean airflow velocity and volumetric flow.

The commissioning procedure must include this range of tests.

15.3.4. Electrical Supply Validation

The electrical power provider should undertake its normal commissioning process and ensure that the supply is appropriate in both normal and emergency situations. UPS and stand-by systems must also be proven.



15.3.5. Lighting System Validation

Appropriate testing should be undertaken to ensure that lighting levels are as required for the various conditions encountered in both day and night in the different zones of the tunnel in accordance with the relevant Australian Standards. The system should also be tested to ensure that the stand-by lighting, designed for evacuation, functions as required. The visibility of exits and the pathways to the exits should be assessed.

15.3.6. Drainage Validation

While it may not be feasible to test for the design flood, it is appropriate to test the drainage system for flows associated with washing and firefighting. Such flows should be applied and appropriate observations and measurements undertaken to ensure that all networks are functioning appropriately. The flame traps incorporated in the system should also be tested. Drain pumps should be tested to the design specifications.

15.3.7. System Integration

It is necessary to test that the various operating systems are properly integrated and operating in concert with each other. Real-time physical trial scenarios should be enacted to ensure that the systems will cater for foreseeable incidents and that the police, fire services, emergency services and tunnel operator teams are familiar with, and can perform their required roles in the event of an incident.

Where individual components are controlled by and/or interface with the control system, the testing needs to ensure components can be operated as required, and that the interfaces function as designed. In addition and where appropriate, the failure modes for each of the components should be tested.

15.4. Commissioning Records

15.4.1. General

Upon completion of a commissioning stage and prior to commencement of the next stage of commissioning, a document should be prepared and signed by a competent person, setting out the following:

• details of component/systems tested or commissioned

• results of any measurements

• any pertinent observations during commissioning

• actions taken to rectify any non-conformance (corrective actions)

• statement as to conformance with acceptance criteria

• date of tests undertaken and date of the report

• signature of person responsible.

Commissioning records should include descriptions of the procedures adopted and the results. All records should be designed to provide appropriate information and guidance to the operators of the tunnel. Where possible, the records should be designed in a format to facilitate the documentation of the ongoing inspection and testing regime during operation of the tunnel.

The documentation should be provided in a form that assists the operator in the day-to-day safe operating needs as well as the needs of periodic inspection.

All manufacturers’ documentation including operating and maintenance manuals, performance specifications and warranty certificates should also be provided as part of the total commissioning package.



15.4.2. Inspection Checklists

Appropriate checklists for all testing procedures (inspection and test plans) should be developed for the commissioning process. The format of the checklists should be such as to provide a suitable recording system for future maintenance and checking processes. The checklists should be designed for clear and simple entry of testing results.

15.4.3. As-built Records

The verified as-built records for the tunnel and its equipment are required to provide the baseline for future maintenance, operation and enhancement of the facility and its systems. Part of the commissioning process should be to ensure that all as-built records are available and properly executed.

As-constructed drawings should contain but not be limited to:

• foundation details

• variations/modifications during construction

• works constructed outside tolerance

• updated geotechnical reports based on actual profile as determined during excavation

• location of all rock anchors including identifying whether the anchors are short-term or long-term

• service/public utility plant (PUP) locations.

15.4.4. Manuals Required

General

It is essential that detailed operating and maintenance manuals be developed for all elements of plant and equipment with in-built procedures for continual improvement based on experience in using them.

Operating and maintenance manuals should cover:

• drawings, including as-constructed drawings

• systems architecture

• systems descriptions

• systems performance

• software architecture and design information

• equipment description

• manufacturers’ technical literature

• any supplementary data available

• operations procedures

• maintenance procedures including expected replacement intervals of parts, test certificates and test reports.

These manuals can be more easily prepared at the design stage in conjunction with the operating personnel than at later stages of the process. They must include any matters that have been included in the design and that are critical to the success of the design in practice. Detailed operation figures/parameters may have to be obtained during the commissioning stage.



Detailed operational procedures at times of emergency must always be readily available to staff.

Operation, inspection and maintenance manual

The operation, inspection and maintenance manual should include but not be limited to:

• operational information on all structures, equipment, systems and procedures (mechanical, electrical, ITS, etc.)

• operational requirements

• inspection frequency (all components)

• details of inspection access requirements (including any confined-space access requirements)

• design life of all components and sub-components – for any component or sub-component that has a design life less than the specified design life of the structure, details for replacement frequency and method for the (sub-) component are required

• routine maintenance schedule including, but not limited to cleaning, wash-down, failed light replacement, incident response systems testing

• scheduled maintenance program including but not limited to

– description of item

– description of defect – intervention level for undertaking the repair of the defect – standard to which the defect is to be repaired

– if appropriate, the inspection time interval required

• details of how routine and scheduled maintenance will be undertaken.

Incident management and recovery manual

An incident management and recovery manual should be prepared and should include, but not be limited to:

• vehicle breakdown

• crashes

• debris on carriageway

• spills

• lost loads

• over-height vehicles

• external electrical supply failure

• flood

• water on pavement

• fire

• explosion

• serious release of noxious liquid or gas

• incident management training (including any in-tunnel incident trials/simulations/tests).



Police, fire and emergency services manuals

A manual for the guidance of police, fire and emergency services expected to attend the tunnel in emergencies should be prepared. The manual should describe the principal features of the tunnel, including the operational procedures, and detail the facilities available to assist them in dealing effectively with incidents and emergencies in the tunnel.

Each service should contribute to the development of the operating manual to cover the specific requirements for response to emergencies in the tunnel involved, making reference as appropriate to any relevant service manuals.

15.5. Operational Readiness

15.5.1. General

The commissioning process requires ensuring that the tunnel is in operational readiness and that it will perform safely and effectively. This requires the infrastructure, the personnel and the documentation to be ready. Until all three are achieved, the tunnel should not be opened to traffic.

15.5.2. Infrastructure Readiness

Infrastructure readiness means that the installation, testing and commissioning of all components of the tunnel has successfully been completed and all remedial actions closed out.

The tunnel should not be opened to traffic until all of the components and/or systems have been tested and proven acceptable, the operating personnel have been trained appropriately and the required documented procedures are completed.

The commissioning process may reveal systems, procedures and equipment that are not functioning or functioning at a lesser level than required. Such deficiencies should be rectified before opening but it may be possible to devise an operational strategy that allows the tunnel to operate safely while the rectification is carried out. Appropriate procedures must be developed and documented prior to opening to allow this to happen. Such arrangements are an interim measure and the rectification process should be completed as quickly as possible after opening to allow normal operations to be implemented in an agreed time frame.

This process should be a last resort to allow earlier usage of the investment in the tunnel infrastructure and may only be used for non-critical issues. If a suitable safe work-around procedure cannot be devised to overcome an issue before the defect is rectified, then the tunnel should not be opened to traffic until it is resolved.

15.5.3. Personnel Readiness

Personnel include the owners, operators, maintainers and users of the completed infrastructure, including emergency services. For operational readiness, each of these groups will require recruitment, training and/or access to information.

Prior to opening a tunnel an exercise should be conducted with the emergency services and should be considered part of the pre-incident planning for emergency services, and familiarisation and training of the operators and other involved parties. The exercise should as far as possible replicate the likely genesis of a real incident (e.g. fire), including the operator response and emergency services response. Video and written records should be retained for training and familiarisation of future personnel.



Control room operators should be trained to the Australian National Qualification TLI42513 – Certificate IV in Traffic Operations. As a minimum to operate unsupervised, the control room operator should attain and demonstrate the competencies of the core units. The remainder of the competencies should be attained within 18 months of employment.

Early involvement of an experienced tunnel operator can assist with operational readiness and familiarity with the tunnel operational systems.

15.5.4. Documentation Readiness

The documentation consists of records that are required to own, operate, maintain and use the completed infrastructure as described in Section 15.2.6, Section 15.3.1 and Section 15.4. Each project will attract its own set of documentation requirements such as statutory approvals and licences.

15.6. Continuous Improvement

The commissioning process may reveal areas where the design and/or operating procedures can be improved and should be modified to achieve improvement. It is necessary to have a procedure in place to provide for the improvements to be documented and implemented as the tunnel operates. Such a procedure should also include a commitment to seeking continual improvements in the operating regime over the life of the facility Procedures should be developed in accordance with AS/NZS ISO 10005: 2006.



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AS/NZS 3000: 2007, Electrical installations (known as the Australian/ New Zealand wiring rules).

AS/NZS 3439.1: 2002, Low-voltage switchgear and control gear assemblies: type-tested and partially type-tested assemblies.

AS/NZS 3947.4.3: 2000, Low-voltage switchgear and controlgear: contactors and motor starters: A.C. semiconductor controllers and contactors for non-motor loads.

AS/NZS 60079.10.1: 2009, Explosive atmospheres: classification of areas: explosive gas atmospheres, (IEC 60079-10-1, Ed.1.0(2008) MOD).

AS/NZS 60079.14: 2009, Explosive atmospheres: electrical installations design, selection and erection, (IEC 60079-14, ed. 4.0(2007) MOD).

AS/NZS 60598.1: 2013: Luminaires: general requirements and tests, (IEC 60598-1, Ed. 7.0 (2008) MOD).

AS/NZS 60598.2.1: 2014: Luminaires: particular requirements: fixed general purpose luminaires.

AS/NZS 60598.2.3:2015 Luminaires - Particular requirements - Luminaires for road and street lighting (IEC 60598-2-3, Ed. 3.1 (2011) MOD)

AS/NZS 60598.2.22: 2005: Luminaires: particular requirements: luminaires for emergency lighting, (IEC60598-2-22, Ed. 3.1(2002) MOD).

AS/NZS ISO 10005: 2006, Quality management systems: guidelines for quality plans.

AS/NZS ISO 31000: 2009, Risk management: principles and guidelines.

NZS 1170.5: 2004, Structural design actions: earthquake actions: New Zealand.

NZS 3101.1&2: 2006, Concrete structures standard.

NZS 6806: 2010, Acoustics: roads: traffic noise: new and altered roads.

SA/SNZ TS 1158.6:2015 Lighting for roads and public spaces - Luminaires – Performance.

International Standards

BS EN 1537: 2013, Execution of special geotechnical work: ground anchors, British Standards Institution.

BS 7385-2: 1993, Evaluation and measurement for vibration in buildings: guide to damage levels from groundborne vibration, British Standards Institution.

BS 8006-1: 2010, Code of practice for strengthened/reinforced soils and other fills, British Standards Institution.



BS 8006-2: 2011, Code of Practice for strengthened/reinforced soils and other fills: soil nail design, British Standards Institution.

BS 8081: 1989, Code of practice for ground anchorages, British Standards Institution, (partially replaced by BS EN 1537).

DIN 4150-3: 1999, Vibration in buildings: part 3: effects on structures, German Institute for Standardisation.

NS 8141-1: 2012+A1: 2013, Vibration and shock: Guideline limit values for construction work, open-pit mining and traffic: part 1: effect of vibration and air blast from blasting on constructions, including tunnels and rock caverns, Standards Norway (in Norwegian).

NS 8141-2: 2013, Vibration and shock: guideline limit values for construction work, open-pit and pit mining and traffic: part 2: effects of vibration on construction works from construction activities other than blasting, and from traffic, Standards Norway (in Norwegian).



Appendix A Horizontal Curves and Sight Distance

In Table A 1, Table A 2 and Table A 3:

• V denotes the design speed in km/h

• SSD denotes the stopping sight distance.

Designers are referred to the Guide to Road Design Part 3: Geometric Design (Austroads 2016) for detailed information on design speed and sight distance.

The tables have been developed using the following parameters:

Perception/reaction time: 1.5 sec. up to 90 km/h and 2.0 sec. above 90 km/h

Car deceleration rate: 0.46 g

Truck deceleration rate: 0.29 g.

Note that the type and height of concrete barrier may improve the available sight distance and allow a consequent reduction in the minimum curve radius when the vertical alignment is on a constant grade or on a sag vertical curve. The effect of this is difficult to calculate and assistance from visualisation software may be needed.

Table A 1: Minimum radius curve to provide car SSD (m)

Eye position in centre of lane, object in centre of lane

V, km/h Car SSD, m 0.5 m shoulder

1.0 m shoulder

1.5 m shoulder

2.0 m shoulder

2.5 m shoulder

3.0 m shoulder

40 30 51 42

50 42 99 81 69 59 52

60 56 173 142 120 104 92 82

70 71 280 230 194 169 149 133

80 88 430 353 299 259 228 204

90 107 635 519 439 380 336 300

100 141 1105 906 766 664 586 524

110 165 1505 1233 1043 904 798 714



Table A 2: Minimum radius curve to provide truck SSD on left-hand curve

Eye position 0.6 m right of centre of lane, object in centre of lane

V, km/h Truck SSD, m

0.5 m shoulder

1.0 m shoulder

1.5 m shoulder

2.0 m shoulder

2.5 m shoulder

3.0 m shoulder

40 38 72 60 52 45

50 55 147 123 106 93 82 74

60 74 268 224 192 168 150 135

70 96 449 375 322 283 252 227

80 120 708 592 509 446 397 358

90 147 1066 891 766 671 597 538

100 177 1543 1290 1108 972 865 779

110 210 2164 1809 1554 1362 1213 1093

Table A 3: Minimum radius curve to provide truck SSD on right-hand curve (m)

Eye position 1.1 m right of centre of lane, object in centre of lane

V, km/h Truck SSD, m

0.5 m shoulder

1.0 m shoulder

1.5 m shoulder

2.0 m shoulder

2.5 m shoulder

3.0 m shoulder

40 38 108 84 68 58 50 44

50 55 221 170 139 117 101 89

60 74 401 310 253 213 184 162

70 96 673 520 424 358 309 273

80 120 1063 821 669 565 488 430

90 147 1599 1236 1007 849 735 647

100 177 2315 1789 1457 1230 1064 937

110 210 3246 2508 2044 1724 1491 1314



Appendix B General Classification of Ventilation Systems

The following general classification of road tunnel ventilation systems is sourced from PIARC (2011): Operating Strategies for Emergency Ventilation.

Longitudinal ventilation

Figure B 1: Longitudinal ventilation with jet fans

Figure B 2: Longitudinal ventilation with saccardo nozzle



Semi-transverse ventilation

Figure B 3: Semi-transverse ventilation: during normal operating conditions: fresh air injection

Figure B 4: Semi-transverse ventilation with remotely controlled dampers



Transverse ventilation

Figure B 5: Transverse ventilation system with uniform supply and extract of air

Figure B 6: Transverse ventilation with remotely controlled dampers

Note: In case of fire, only the dampers near to the fire are opened. All others are closed.

Massive point extraction

Figure B 7: Massive point extraction system

Combined Ventilation Systems

A tunnel can include several ventilation methods. For example, the length of the tunnel may be subdivided into sections e.g. one section with jet fans for longitudinal ventilation and another section with transverse ventilation. In such cases the ventilation systems in the sections adjacent to the fire incident location would be used to optimise the smoke management.