Highway Infrastructure Skid Resistance Strategy

Document Control

Date Ref Revision Comments Author Check Review Approved

19/05/17 0.1 DRAFT First CS SGP -

-

15/06/18 0.2 DRAFT Amendments CS SGP D.Group -

16/08/18 1.0 FINAL Amendments CS SGP S.Board LA

Contents

Detail Page

Introduction & Objectives 1

Alignment to Bournemouth Corporate Objectives 2

Highway Authority Legal Responsibilities & Scope 2

Process 4

Process for Maintaining and Managing Network Skid Resistance 5 -11

Appendix A: Initial Desktop Investigation Report Template 12

Appendix B: Detailed Site Investigation Report Template 13-14

Acronyms & Supporting Documentation 15

Glossary 16

1

Introduction Bournemouth Borough Council (BBC) understands the importance of managing skidding resistance on its Highway Network. The approach to skidding resistance supports the aims and objectives set out in Bournemouth Council’s Highway Infrastructure Asset Management Policy (HIAM). This strategy describes how the provision of appropriate levels of skid resistance will be managed to meet the advice and guidance contained within the Design Manual for Roads and Bridges (DMRB) HD 28/15. This provides details on surface characteristics necessary to deliver the required skid resistance properties, which is essential to ensure consistent skid resistance throughout the life span of a carriageway. In this document, the term ‘skid resistance’ refers to the frictional properties of the road surface measured using a specific device under standard conditions. The term always refers to measurements made on wet roads, unless specifically stated otherwise. These measurements are used to characterise the road surface and assess the need for maintenance, but cannot be related directly to the friction available to a road user making a manoeuvre at a particular time. This document should be read in conjunction with BBC HIAM Policy and Strategy.

Strategy Statement Bournemouth Borough Council’s Skid Resistance Strategy will help deliver a safer highway network for road users by managing the risks associated with wet skidding incidents.

Objectives The objectives of the Councils’ Skid Resistance Strategy are to:

▪ To set out the strategy for monitoring and managing skid resistance on the

road network;

▪ To define the appropriate investigatory levels (ILs) for individual sections of

carriageway;

▪ To set out the strategy for prioritising further investigation of sites that fall

below the site IL;

▪ To improve safety on the network in order to help reduce the number of road

traffic casualties & claims

▪ To demonstrate that skid deficient sites are prioritised and programmed in a

consistent manner by the Council whilst taking into account budget, and

programme;

▪ To demonstrate compliance with best industry practice contained within ‘Well-

Managed Highway Infrastructure’ - A Code of Practice 2016

2

Alignment to Corporate Objectives

This strategy helps to achieve our long-term objectives for managing highway infrastructure and aligns to BBC corporate objectives. As set out in BBC’s Corporate Plan Ambition 2020 - Building a Better Bournemouth, there are four key priorities linked to HIAM, namely: - An Efficient Council – Delivering value for money services and making the best use of our assets An Active Community - Connecting residents, businesses and visitors to improve community integration and enhance a sense of place in Bournemouth. An Improving Environment - Providing high quality infrastructure for residents, businesses and visitors while protecting and enhancing our beautiful environment with improving resilience from climate change. A Thriving Economy – Maintaining access to continue to ensure Bournemouth is one of the UK’s premier tourist destinations The successful achievement of these objectives relies on a well maintained and managed highways network to facilitate movement in a safe and reliable manner

Key Influences This strategy supports the levels of service contained within the Highway Infrastructure Asset Management Strategy by ensuring the carriageway network is well maintained and safe. The implementation of the processes that are part of this Strategy will ensure the highest risk sites are investigated and identifies which of those sites require treatment. Consistent application of this strategy will provide important documentary evidence of how skid resistance is managed on the carriageway network.

Highway Authority Legal Responsibilities Bournemouth Borough Council acting as the Highway Authority has a statutory duty under Section 41 of the highways act to maintain highways maintainable at public expense. Although the formal management of highway skid resistance is not a legal requirement it is considered good practice and aligns with our HIAM Policy, Strategy and Well Managed Highway Infrastructure. - Code of Practice (CoP) Section 58 of the highways Act 1980 provides the ability to form a statutory defense to counter legal actions for negligence. The Council must be able to prove in a court of law that it “…had taken such care as in all the circumstances was reasonably required to secure that the part of the highway to which the action relates was not dangerous for traffic.”

3

Scope This strategy applies to BBC highway network. Mechanical skid resistance surveys will be carried out on our principal roads, classed as Category 2 and Category 3a hierarchy types annually. Category 2 and 3a hierarchy descriptions can be seen below. Category 2 – Strategic Routes Routes for fast moving long distance traffic with little frontage access or pedestrian traffic. Speed limits are usually more than 40 mph and there are few junctions. Pedestrian crossings are either segregated or controlled and parked vehicles are generally prohibited. Category 3a - Main Distributors Routes between Strategic Routes and linking urban center’s to the strategic network with limited frontage access. In urban areas speed limits are usually 40 mph or less, parking is restricted at peak times and there are positive measures for pedestrian safety. Remaining Hierarchy Where a specific collision problem is highlighted because of wet skidding on category 3b, 4a and 4b roads then an investigation may be carried out in line with part of the process relating to investigation, documented in Appendix A. Carriageway sections excluded from strategy Investigatory levels will not be defined for sections as below and as such will not be subject to routine investigations. When required specific site testing of areas may be undertaken in accordance with National Guidance.

▪ Traffic calmed areas

▪ Modular paved areas

▪ Areas with physical restrictions

▪ Pedestrianised areas

4

Process Full details of the process for monitoring and managing skid resistance are set out in Appendix A. It briefly comprises of annual SCRIM (Sideways Coefficient Routine Investigation Machine) surveys, used to identify sites where skid resistance is below the required level. The site categories and IL’s were reviewed in January 2017 by WDM Ltd and updated in Pavement Management System (PMS) for the Category 2 and 3a network to be surveyed by SCRIM annually. Appendix A Table 2 lists the site categories used along with associated site codes. The level of skid resistance required depends on the individual site characteristics. Each site has a specific investigatory level which is documented in Table 2 of Appendix A.

Initial Investigation will comprise of the following stages;

1. Identify sites at or below the Investigatory level

2. Identify other sites requiring investigation

3. Data Validation

4. Identify sites for detailed investigation

Initial Investigations shall be undertaken in accordance with diagram 1 Appendix A. The objective is to determine whether a surface treatment is justified to reduce the risk of vehicles skidding, whether some other form of action is required, or whether no action is currently required. Detailed site investigation and prioritisation;

1. Collate data

2. Plan investigation

3. Carry out investigations

4. Prioritise and programme maintenance

A detailed investigation is carried out in accordance with diagram 2 Appendix A, to collate and access the information available for each site in order to reach a decision about the best course of action.

Measures of Effectiveness

The effectiveness of this strategy can be measured against the following criteria:

• The percentage of the network hierarchy 2 and 3a where SCRIM is below investigatory level;

• The trend in the number of slight injury collisions (and KSIs) where the

carriageway condition or skidding on wet roads has been identified as a

contributory factor;

• The recommended treatments completed;

5

Process for Maintaining and Managing Network Skid Resistance Stage 1 – SCRIM surveys Single Surveys to calculate Characteristic SCRIM Coefficient CSC will be carried annually. Surveys will be carried out on the category 2, and 3a road network during periods as defined in Table 1. One survey period will be completed annually. The CSC will be assessed in relation to the Investigatory Levels. SCRIM vehicles undertaking surveys will be accredited by the Transport Research Laboratory (TRL) in conjunction with Highways England (HE) annual trials.

Table 1 Timing of the Surveys

Survey period Season Timing

Early 1st May - 20th June

Middle 21st June – 10th August

Late 11th August – 30th September

SCRIM survey data will be held and updated annually in the PMS. Additional sites will also be selected where;

1. Known history of accident occurrence being more frequent than normal,

(i.e. injury accidents within a 3-year period) or greater occur in wet

conditions.

2. Other sites where skidding is reported and where there is notable

potential for conflict between road users, particularly where the outcome

is likely to have severe consequences including:

3. In liaison with Council’s Road Safety Team.

These will be carried out using an appropriate method e.g. Griptester, Pendulum or SCRIM surveys.

HD28/15 recommends a 3-yearly review of the Site Category and Investigatory Levels, as well as a process of updating as the network changes. By undertaking this site category review BBC can be confident that the SCRIM survey is identifying ‘high risk’ sites, and that resources to investigate sites are appropriately deployed.

6

Table 2 – Site Investigatory Levels Bournemouth Council

Code Site Category Investigatory Level (IL)

Distance (km)

B Dual non event 0.35 19.266

C Single non event 0.40 22.099

QL-U Approach to junction urban - low <40mph 0.45 19.402

QL-R Approach to junction rural - medium >40mph 0.50 0.48

QM-U Approach to roundabout urban - low <40mph 0.45 2.858

QM-R Approach to roundabout - medium >40mph 0.50 0.074

K Approach to crossing 0.50 8.812

G1 Gradient 5- 10% 0.45 0.924

R Roundabout 0.45 3.228

D500 Dual bend < 500m 0.45 1.139

S100 Single bend < 100m 0.45 0.778

S500 Single bend 100 - 500m 0.45 0

Total - Road Categories 2 & 3a 79.06

7

Stage 1 – Initial Investigation Following receipt of the CSC values, an initial review of the data will be carried out following the process below. The Initial investigation will be completed prior to the collection of the subsequent year’s survey. Initial investigations will be undertaken by a competent person with Highway Asset Management experience using the initial site investigation template Appendix A.

8

Initial Investigation – Site Score Matrix

The site score matrix referred within Table 4 is used as part of the initial investigation process to determine the site risk based on SCRIM deficiency and recorded accident data. A site is defined as 100m, or by the site category (Table 2) if this is less than 100m.

Any segment within the site that has a score greater than or equal to 5 then should continue to the detailed investigation process. Segments are continuous lengths with the same Site Category and IL. Segments should also have similar levels of skid resistance.

Table 4

Skid resistance Difference (SD)

>0 >-0.05 & ≤0

>-0.10 & ≤-0.05 >-0.15 & ≤-0.10 ≤-0.15

Score

STOP 1 2 3 4

Number of wet accidents over 3-year period

0

1

2

3+

-

Score

0 2 4 6 -

Worked example: Skid resistance Difference (SD) >-0.05 and ≤0 Scores 1 Number of wet accidents over 3-year period = 2 Scores 4 Total site score = 5

Skid resistance Difference (SD)

>0 >-0.05 & ≤0

>-0.10 & ≤-0.05 >-0.15 & ≤-0.10 ≤-0.15

Score

STOP 1 2 3 4

Number of wet accidents over 3-year period

0

1

2

3+

-

Score

0 2 4 6 -

Detail Investigation triggered greater than or equal to 5

Action = Move to Stage 2 Detailed Investigation

9

Stage 2 – Detailed Investigation Detailed investigations will be undertaken by Road Safety RoSPA qualified person using the site investigation template Annex B. The main objectives are:

▪ To determine whether a surface treatment is justified

▪ To determine whether some other form of action is required

▪ To determine whether the site should be kept under review

▪ To determine whether the IL is appropriate.

10

Use of Slippery Road Warning Signs Slippery road warning signs should be erected to warn drivers of sites where skid resistance is low and may result in an increased risk of collision

11

Stage 3 Treatment Priority will be given to sites where the detail site investigation has shown that a treatment would make a positive contribution to the safety all road users.

Where investigations show that treatment is necessary consideration will be given to other planned maintenance works programmes to ensure potential efficiencies. Treatments will be programmed and will be dependent on capital budget allocations, required treatment and estimated costs. Realistic time frames for treatments must be permitted, to allow for mobilisation of resources. The appropriate treatment will be specific to the individual site. Treatment selection will follow the guidelines set out in the DMRB.

Changes to the Road Network Future road schemes introducing changes on the network that will influence the level of skid resistance required will be designed to provide adequate skid resistance. When the scheme is completed the revised IL for the site will be updated in the PMS

12

Appendix A - Initial Desktop Investigation Report Template

Completed Initial Investigations to be retained for record purposes

Initial Desktop Investigation Report

Date: Investigation by: Ref No: Year/section

Current Site Category & IL Deficiency range Route/Section

Check with Annual work programme

Treatment since survey Yes No

Site in future works programme Yes No

Pavement Condition

Skid resistance and texture depth

Other aspects of pavement condition

Crash Data

Period Number of crashes Analysis length

From To Total Wet Wet skid

Length (km) Traffic AADT

Accident code:

Other comments on crash data

Forward to Detail Investigation Signature Date Approved by

Yes No

13

Appendix B Site Investigation Report Template

Completed Investigations to be retained for record purposes

Site Investigation Report

1. General:

Date: Time Inspected by Survey Type

Walked Driven

Weather

Reason for visit Low grip tester or scrim

Routine review

Accident report

Dates of any previous visits

Document reference

2. Site Details

Road classification

Road Name

Investigatory Level

Have any layout changes been made to the site since Investigatory Level was assigned

Yes

No

Comment

3. Visual Assessment

Surfacing type

HFS

HRA

SMA

HS

SD

MA

OTHER

Surface condition/texture

Very good

Good

Poor

Very Poor

Presence of debris or other contamination:

Yes

No

Comment

Local defects (potholes, fatting up etc.)

Yes

No

Comment

highway drainage serviceable

Yes

No

Comment

Are there any issues with surface profile

Yes

No

Comment

14

4. Road users

Volume of traffic: (High-Medium-Low)

H

M

L

Comment

Traffic Type

P/cycle

M/Cycle

Car

LGV

OGV 1

OGV 2

BUS

Traffic speeds in relation to road layout

Low

Normal

Excessive

Evidence of crash damage Yes

No

Comment

5. Road Layout

Is the layout appropriate for vulnerable road users?

Yes

No

Comment

Are junctions appropriate for turning manoeuvres

Yes

No

Comment

6. Markings Signs and Visibility

Are traffic signs, signals, road markings in good condition and clearly visible

Yes

No

Comment

Clear sight lines/visibility of queues/vegetation

Yes

No

Comment

7. Additional Information

8. Recommendation

Is treatment required Y N (If no stop)

Review IL Y N

What type of treatment Y N

Review routine maintenance Y N

Other action required Y N

9. Approval

Print Name Signature Date Approved by Date

15

Acronyms

BBC Bournemouth Borough Council

CoP Code of Practice

CSC Characteristic SCRIM Coefficient

DMRB Design Manual For Road and Bridges

DfT Department for Transport

HIAM Highway Infrastructure Asset Management

HE Highways England

IL Investigatory Level

Km Kilometres

PMS Pavement Management System

RoSPA Royal Society for the Prevention of Accidents

SCRIM Sideways Force Coefficient routine Investigation Machine

TRL Transport Research Laboratory

Supporting Documentation BBC Corporate Plan http://www.bournemouth.gov.uk/CouncilDemocratic/AboutYourCouncil/PlansandPerformance/CorporatePlan.aspx

DMRB HD28/15 - Skidding Resistance - http://www.standardsforhighways.co.uk/ha/standards/dmrb/vol7/section3/hd2815.pdf Well Managed Higwhay Infrastructure - http://www.ukroadsliaisongroup.org/en/utilities/document-summary.cfm?docid=4F93BA10-D3B0-4222-827A8C48401B26AC

BBC HIAM Policy - http://www.bournemouth.gov.uk/Streets/Streetsdocuments/hiam-policy.pdf BBC HIAM Strategy - http://www.bournemouth.gov.uk/Streets/Streetsdocuments/hiam-strategy.pdf

16

Glossary of Terms Skid resistance – the frictional properties of the road surface when measured using a specific method. The skid resistance refers to a road in wet conditions and characterise the road surface and assess the need for maintenance. Investigatory Level (IL) - A warning level for skid resistance. The investigatory level is the level of skid resistance at which a site investigation should be carried out to assess the need for action. Bournemouth Council’s ILs are based on a review conducted by WDM in 2017 which were derived from recommendations documented in HD28/15. Griptester – is a three wheeled trailer that is typically towed behind a small vehicle. The device uses longitudinal friction to measure skid resistance. The Grip Number (GN) can be easily converted to SCRIM equivalents for ease of evaluation against defined ILs Pendulum tester – the apparatus consists of a portable pendulum device supported on a stand with a spring-loaded rubber slider projecting from the underside.The stand is adjusted so that when the pendulm swings,the rubber slider makes contact with the surface. The final height reached by the pendulum is indicated on a scale calibrated in skid-resistance values that relate to energy lost to friction during the slide.

Site - A single location, bend, junction, or short length of carriageway. SCRIM - Sideways Force Coefficient Road Investigation Monitor

ESC - Equilibrium SCRIM Coefficient – The mean of Scrim Coefficient taken over 3 years taking into account seasonal effects. CSC - Characteristic SCRIM Coefficient – Skid resistance value. PMS - Pavement Management System – software used to provide management data on road condition TRL - Transport Research Laboratory provide innovative research, technology and software solutions for surface transport modes and related markets of automotive, motorsport, insurance and energy. Well-maintained Highways: Code of Practice for Highway Maintenance Management A Local Government highway management guidance document encouraging asset management principles and planned maintenance of roads.