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Road Design Note 03-07 of 10 Working Release v1.0 July 2017

Road Design Note

Raised Safety Platforms (RSP) RDN 03-07 July 2017

This RDN has been published as a WORKING RELEASE. If you have any comments on its content, could you please forward them to the VicRoads Safe System Design team by the end of October 2017. An updated version is expected to be published early December 2017.

1. Purpose This Road Design Note (RDN) provides guidance for the design of Raised Safety Platform (RSP) treatments, including:

• ramp profile and location

• signing and pavement marking

• key design consideration

• post implementation monitoring and evaluation.

The guidance provided in this RDN is based on information currently available and best practice. As RSPs are a relatively new treatment on arterial roads, this document is expected to evolve over the next 12 months. Users are advised to seek the latest version.

2. What is a raised safety platform? VicRoads’ approach towards a Safe System requires practitioners to recognise that humans, as road users, are liable to errors and will continue to make mistakes. In a Safe System, roads should be designed to reduce the severity of injury when crashes inevitably occur.

RSPs are speed management treatments capable of reducing the maximum comfortable operating speed for a vehicle, and lowering the overall speed of vehicles closer to a Safe System collision speed.

RSPs may be designed for a range of vehicle speeds and types. Design speeds ≤ 50km/h are encouraged to reduce the side-impact severity for a vehicle to a survivable level, i.e. a Safe System collision speed. Design speeds ≤ 30km/h are encouraged to reduce the severity of any pedestrian related crashes to a survivable level.

The implementation of RSPs should include supporting treatments to achieve the desired outcome.

When installing RSPs at intersections, the entire intersection can be raised with approach and departure ramps. RSPs can also be placed on the approach to an intersection (sometimes referred to as raised stop bars) in order to achieve a similar outcome.

On local roads and low speed arterial roads, RSPs can be installed in mid block locations as a traffic calming device or to improve safety at pedestrian crossings.

RSPs could be painted and paved to further increase driver awareness and highlight the presence of the platform on approach to the intersection.

3. Scope This Road Design Note is applicable to RSPs in the following locations, with a focus at the moment on posted speeds of 70km/h or less:

• intersections (uncontrolled or controlled)

• roundabouts

• pedestrian crossings (uncontrolled or controlled)

• mid-block locations.

RSPs have not been widely implemented on arterial roads, particularly those with an operating speed of 80km/h and

Road Design Note 03-07 - Raised Safety Platforms (RSP)


above. As such, the overall benefit and risk including noise implications have not yet been thoroughly evaluated or documented.

Achieving an operating speed of ≤ 50km/h through an intersection is a significant reduction in speed from 80km/h. Therefore, additional speed management treatments should be considered to gain the expected speed reduction. Further thought of moving towards Safe System speeds is being considered with the intention of including guidance for the placement of RSPs in 80km/h speed zones in this document.

In the interim, practitioners considering the use of RSPs on higher speed roads should consider the principles contained within this document while seeking expert design guidance from VicRoads Safe System Design (SSD) team & Safe System Road Infrastructure Program (SSRIP) team to understand road function, context and risks.

4. Design guidance

4.1. General Key elements for consideration when designing RSPs should include:

• effectiveness of the RSP to reduce speeds

• vehicle types (including large or special vehicles) and turning movements, particularly truck stability

• vertical grade through intersections and approach to intersection

• minimum ground clearance for light and heavy vehicles

• pedestrian crossing locations

• horizontal and vertical sight distance to the platform (desirably approach sight distance)

• impact and delay to emergency services, bus service and heavy vehicle operations

• impact on neighbouring streets and service roads

• potential damage to vehicles and pavement

• storm water drainage design

• adequate warning to approaching motorists

• increased queuing and overtaking requirements due to speed disparities between vehicle types

• bus stop locations

• lighting

• noise implications.

Note: while it is acknowledged that RSPs can cause delays to the operation of the transport network, when incorporated with traffic signals or roundabouts, a large component of the delay is already built into these major traffic control items for effective operation.

4.2. Location & orientation RSPs should be orientated perpendicular to the direction of traffic flow so that both front wheels of the vehicle commence to rise or fall on the ramps concurrently. Otherwise the vehicle may travel on the ramps with the wheels at different levels, potentially causing it to become unstable and affect the driver’s ability to operate the vehicle.

4.2.1. Intersections When installing RSPs on the approach to an intersection, ramps must be located clear of the through lanes of the intersecting road.

Ideally, RSP approach ramps should be located beyond the stop line in close proximity to the intersection to ensure that vehicles approach the intersection at lower speed.

Where an approach ramp is installed in front of (prior to) the stop line (e.g. due to heavy vehicle turning movements and stability), the following must be considered:

• potential for vehicles to approach the intersection at higher speeds

• impact on heavy vehicle operation when having to decelerate twice

• efficiency of the intersection (using SIDRA).

If efficiency is unduly affected by the RSPs located in advance as described above, consideration of the RSPs being located centrally within the intersection allowing the ramps, and subsequently the holding lines, to be closer and hence assisting (signalised) operational efficiency is required.

Note: Further guidance is being developed on the determination of RSP location prior to the intersection. In the interim, practitioners are advised to consider the principles contained in this guidance document and make an informed decision to achieve the desired outcome.

If RSPs are installed on turning lanes, ramps should be located in such a manner that allows a turn to be commenced or completed prior to crossing the ramp.

Where there is a high percentage of heavy vehicles using the road, approach ramps should commence at least a length equivalent to the length of the critical stability vehicle prior to turning. See section 4.4.

RSP departure ramp locations should be determined using the turning paths of a design vehicle. Both the front wheels of the vehicle should go down on the ramp concurrently.

“RSPs should lower the likely impact speed within an intersection to a

Safe System speed”



4.2.2. Pedestrian crossings If RSPs are installed in close proximity to pedestrian facilities, pedestrian refuges must be set back a minimum of 1m from the ramp to prevent the possibility of pedestrians mistaking ramp markings for a crossing facility.

Alternatively, a pedestrian crossing may be incorporated into the RSP to minimise any confusion and achieve better pedestrian safety outcomes.

4.3. Profile

4.3.1. Height The typical RSP dimensions recommended in Austroads Guide to Traffic Management (2008) are:

• Desirable height = 100mm

• 75mm may be considered where site constraints and traffic composition suggests a lower height profile (e.g. high truck volume routes). Ramp heights less than 75mm are not effective at reducing speeds and should not be considered

• 150mm may be used for low speed (less than 50km/h) and low traffic volume environments, however, platforms that are over 100mm may damage low-floor vehicles and are not to be used on any arterial roads

Note: The above dimensions have been selected to align with Austroads Guide to Traffic Management (2008)3,9.

4.3.2. Length As stated in Austroads Guide to Traffic Management (2008), the flat section of the RSP is recommended to be extended over more than a standard passenger car length (i.e. at least 6m), including when used as a pedestrian crossing.

Figure 1: Typical RSP Section

Lengths of raised intersection platforms will depend on the size and configuration of the entire intersection.

4.3.3. Ramp grade The recommended approach ramp grades to achieve a Safe System speed are shown in Table 1. The comfortable maximum speed should be designed for 20km/h less than the operating speed of the road.

Table 1: Suggested ramp grades for various speeds

Operating Speed (km/h)

Approach Ramp Grade

Comfortable Maximum Speed

(km/h)

50 1:15 (6.7%) 30

60 1:20 (5%) 40

70 1:25 (4%) 50

Note: Refer Appendix B for additional guidance on ramp grades. Refer VicRoads Supplement to Austroads Guide to Road Design Part 3 for the definition of ‘operating speed’.

Ramp gradients may be designed for higher operating speeds using the methodology included in Appendix B, recognising that the ramp will only provide a ‘Step Towards’ Safe System and an ultimate transformational treatment should be planned in consultation with the Safe System Design team and SSRIP team.

Operating speeds of 80km/h and above will require motorists to reduce their speed by more than 20km/h to achieve the safe collision speed of 50km/h. This speed reduction cannot be achieved by only providing the traffic controls in Section 5, Hence, consideration shall be given to supporting treatments such as, but not limited to:

• gateway treatments

• speed reduction in stages (e.g. multiple platforms with appropriate profiles)

• additional warning signs (e.g. flashing warning signs);

• speed calming line marking

• rumble strips

• permanent speed limit reduction

When selecting supporting treatments, practitioner must consider the principles contained within this document and seek expert design guidance from VicRoads SSD team & SSRIP team to understand the context and risks. Performance monitoring and evaluation is essential, refer Section 6.

Note: RSPs installed in a high speed environment will largely depend on context; e.g. road function, sight line requirements, potential for rear-end crashes and vehicle type & mix.

Ramp gradients steeper than 1:15 (6.7%) require operating speeds <50km/h, which are generally not appropriate for arterial roads. Gradients steeper than 1:15 (6.7%) should also be avoided as they are not considered comfortable for cyclists



and may discourage use (Austroads Guide to Traffic Management 2008).

Easing of ramp gradients to be more considerate of bicycles, buses or low loader trucks should be balanced against the extent of speed reduction required for majority of road users and vehicle types.

Based on previous trials in Victoria, a 1:35 grade is considered appropriate for the departure ramp; flatter slopes may also be appropriate.

4.3.4. Ramp shape RSP ramps must be flat with a consistent grade between the top and bottom of the ramp. Watts, Sinusoidal or other ramp shapes are not to be used (ARRB 2014).

4.4. Consideration of heavy vehicles Practitioners must carefully consider the effect that RSPs will have on heavy vehicles, while recognising that competing objectives must be balanced. Altering the ramp profile to suit heavy vehicles may greatly reduce the effectiveness to slow passenger vehicles and affect the overall safety outcome.

The following are key considerations for heavy vehicles:

• location & orientation of the approach and departure ramps to avoid the critical vehicle instability

• maximum RSP height to avoid critical vehicle instability

• potential operational deficiency and delays due to the lower acceleration and deceleration of heavy vehicles

• potential implications of heavy vehicle drivers using alternate routes (e.g. local streets) to avoid the RSP.

4.4.1. Selection of design vehicle for road design

Design vehicle is the largest vehicle (commercial vehicles in many cases) to regularly perform a turning movement and is the hypothetical vehicle whose dimensions and operating characteristics are typically used to establish traffic lane widths, intersection layout and road geometry. Refer to Austroads Guide to Road Design (AGRD) Part 4 for guidance on the choice of design vehicles to be used for the design of arterial roads and on-road facilities.

4.4.2. Selection of critical vehicle for RSP design

The design process for RSPs must recognise that ramps will likely to be located within the turning path of a heavy vehicle in order to maximise RSP benefits for passenger vehicles. This will thereby increase stability risk for heavy vehicles. It is the designer’s responsibility to include appropriate measures (e.g. appropriate signage) to ensure the driver of a heavy vehicle is alert to the unusual environment and that the RSP will not cause critical instability or truck roll over for minor errors.

Hence, the design of all RSP’s (location, orientation and height) must consider the “critical unstable vehicle”, or low performing vehicle, to ensure the treatment does not present an undue

dynamic stability or roll-over risk to these vehicles. Critical stability vehicle is site specific and should be determined considering the traffic composition, traffic data, designated heavy vehicle routes and permitted heavy vehicles in the area.

For information regarding designated heavy vehicle routes in Victoria, refer ‘Heavy vehicle networks maps in Victoria’ on VicRoads website–https://www.vicroads.vic.gov.au/business-and-industry/heavy-vehicle-industry/heavy-vehicle-map-networks-in-victoria.

At a minimum, a computer simulation assessment (i.e. 3D dynamic modelling) using the proposed RSP configuration and selected critical unstable vehicle (for e.g. 19m semi trailer, B-double or other low profile combinations such as low loader truck) shall be used to assess the effect of RSP on heavy vehicle stability.

Examples of simulation programs that can be used include, but not limited to: PC-Crash (dsd.at), HVE (edccorp.com), or Truck Sim (carsim.com).

4.4.3. Low floor vehicles In accordance with the Australian Design Rule 43 for Vehicle Dimensions and Configurations, the minimum ground clearance for low floor vehicles including heavy vehicles under the conditions of ‘Maximum Loaded Test Mass loading’ is 100mm. When fully loaded, low loader trailers often operate close to the minimum ground clearance of 100mm. Roads that accommodate low loader trucks should have the RSPs designed such that the axle group of the low-loader combination span the flat section of the RSP. To alleviate the risk of low floor vehicles bottoming out, focus should be given to raising the entire intersection instead of placing stop bars.

Figure 2. Examples of low loader combinations

As a general starting point for practitioners, the following may be considered;

• where the volume of a particular heavy vehicle movement is high (e.g. >15%), a maximum RSP height of 75mm should be considered

• where the volume of a particular heavy vehicle movement is extremely high (e.g. >25%), the use of an RSP should be reconsidered or modified for the high volume movement

https://www.vicroads.vic.gov.au/business-and-industry/heavy-vehicle-industry/heavy-vehicle-map-networks-in-victoria).





path (this may include one specific movement through an intersection)

For further guidance on heavy vehicle performance and requirements, contact VicRoads Heavy Vehicle Services team.

4.4.4. Other Road Users Other road users such as buses, motorcyclists, cyclists etc., should be considered in the project risk assessment based on the individual merits and context of the project.

5. Traffic control devices At the time of writing, a specific signing and pavement marking strategy has not been developed for RSPs, therefore all signing and pavement marking shall comply with the requirements of this document and relevant VicRoads Supplements to Australian Standards.

5.1. Warning signs All raised safety platforms shall have warning signs with a recommend advisory speed based on the ‘comfortable maximum speed’ in Table 1.

Warning signs shall include a:

• Road Hump Ahead sign located prior to the approach ramp (refer to T.E.M. Vol 2 for distance requirements) and

• Road Hump and Advisory Speed sign located in-line with the beginning of the approach ramp.

Figure 3: Road Hump Ahead Figure 4: Road Hump with

Advisory Speed Sign

5.2. Warning signs for heavy vehicles Where the RSP is located within the turning path of a heavy vehicle, an appropriate truck tilting warning sign with an advisory speed (refer Figure 5) must be installed prior to the turning lanes at visible locations.

The advisory speed must be site specific and must consider the ramp profile selected and results from the critical stability vehicle simulation (refer section 4.4).

Figure 5: Truck tilting warning signs with advisory speed

5.3. Line marking All line marking shall be white to ensure consistency across the state.

RSP line marking should be selected based on the location, as follows:

• at or beyond the stop line (option 1)

• mid-block or where traffic has an unsignalised right of way through the intersection (option 2).

Option 1: Stop line prior to the ramp The stop line shall be located a minimum of 1.0m prior to the ramp and shall not be located on or beyond the approach ramp. It is expected that drivers may become distracted and less aware of the stop line and signals when negotiating the ramp.

Figure 6: RSP linemarking – Option 1



Option 2: Through traffic Option 2 is suitable where the vehicle has right of way over the RSP. Option 2 may also be used where the configuration of the intersection requires the driver to naturally slow in order to navigate the intersection, e.g. T-intersection or roundabout.

Figure 7: RSP linemarking – Option 2

5.4. Delineation and coloured pavement Additional delineation such as coloured pavement marking is not mandatory, but may be used to improve the conspicuity of the RSP.

Coloured pavements should not be used where line marking is required through the intersection. Where coloured pavement is being adopted, the preferred colour is light grey or terracotta red. Green pavements should be avoided unless justification from other guidance can be provided.

“RSPs may use a light grey or terracotta red pavement colour”

5.5. Street lighting All RSP treatments should be illuminated in accordance with AS/NZS 1158:2015 - Lighting for roads and public spaces.

6. Performance monitoring & evaluation

Given the relatively new implementation of these treatments on arterial roads, selected projects incorporating RSPs under SSRIP will be subjected to performance monitoring to help inform future guidance.

For projects outside SSRIP, performance monitoring and evaluation is warranted if the implementation of a RSP contains new design or innovative elements.

Performance monitoring shall include, but not limited to:

• pre-installation speed distribution (e.g. 50m and 100m prior to the intersection centre, through the intersection and 50m and 100m after the intersection centre)

• post-installation speed distribution at above locations (12 months after)

• noise assessment (pre and post installation)

• road user (trucks, busses, emergency vehicles, cyclists, motorcyclist etc.,) reaction post-implementation via feedback

• video footages to capture vehicle performance and behaviour approaching platforms.

Speed distribution data can be gathered using cameras, speed tubes or T.I.R.T.L. (The Infra-Red Traffic Logger).

For evaluation needs and further guidance on performance monitoring sites, contact VicRoads SSRIP team. The SSRIP team contact at the time of publish is Amir Sobhani.

SSRIP, 1, McNab Avenue, Footscray, Vic 3011 Phone: (03) 8572 7992 Email: [email protected]

References 1) ARRB Research Report, Innovative Raised Stop Bars at Signalised

Intersections; Report No. 008159 (ARRB 2014).

2) ARRB Contract Report, Innovative Safety Platform Trials, Report No. 009261 (ARRB 2015).

3) Austroads Guide to Traffic Management, Part 8: Local Area Traffic Management (Austroads 2008).

4) Australian / New Zealand Standard 1158:2015 – Lighting for roads and public spaces (Australian Standards 2015).

5) Austroads Research Report, Achieving Safe System Speeds on Urban Arterial Roads, AP-R514-16 (Austroads 2016).

6) Kjemtrup, K 1988, ‘Speed reducing measures’, ARRB Conference, 14th, 1988, Canberra, ACT, ARRB Group, Vermont South, Vic, vol. 14, no. 2, pp. 125-32.AASHTO, 2011, Roadside design guide.

7) Towards Zero Safe System Road Infrastructure Program (2017).

8) VicRoads Supplements to Australian Standards (VicRoads 2016).

mailto:[email protected]



9) VicRoads Supplement to Austroads Guide to Traffic Management Part 8 (VicRoads 2008).

10) Watts G. R. (1973), ‘Road Humps for the control of vehicle speeds’, TRRL Report LR 597.

Appendices: APPENDIX A: Examples

APPENDIX B: Ramp Grade Selection

APPENDIX C: Typical Case Study

For information and suggestions please contact: VicRoads Safe System Design team, 60 Denmark St, Kew Vic 3101 Email: [email protected]

Road Design Note 03-07 – Revision Summary

Issue Approved Date Amendment

03-07 M-SSD July 2017 First edition

Road Design Notes are subject to periodic review and may be superseded.

mailto:[email protected]



Appendix A - Examples

Ramp profile - SurfCoast Hwy/Kidman Ave, Geelong, Victoria

Artist image of raised platform at SurfCoast Hwy/Kidman Ave

Signing at SurfCoast Hwy/Kidman Ave raised platform

Advance Signing – approach to SurfCoast Hwy/Kidman Ave

raised platform

City of Greater Dandenong, Victoria

City of Gold Coast, Queensland

City of Charles Sturt, South Australia



Appendix B – Ramp grade selection

Background: Drivers are subjected to vertical acceleration when traversing vertical displacement devices such as raised platforms. Therefore, raised platforms were identified as a potential measure for managing speed.

The vertical acceleration that a person is subjected to passing over a road hump mainly depends on the geometric design of the hump and vehicle speed. Minor effects include vehicle type and axel separation.

There is a linear correlation between the vertical acceleration a person is subjected to and this person’s perception of comfort. The greater the vertical acceleration, the more uncomfortable the driver feels.

An international limit value has been established for the maximum vertical acceleration a person should be subjected to over a short period of time i.e. 1.0 g (9.8m/s2) - the acceleration of gravity). Speed reduction can be achieved when vertical acceleration exceeds a comfort threshold (0.5 g). Vertical acceleration exceeding 0.7 g could cause damage to vehicles. Vertical acceleration less than 0.5 g is comfortable and has no speed reduction (Kjemtrup, K 1988). Refer to Table B1 for the summary of these findings.

Table B1. Typical driver speed response to vertical acceleration

Magnitude of vertical acceleration (g) Typical driver response

0.1 – 0.5 No speed response

0.5 – 0.7 Some speed reduction

0.7-1.0 Possible damage to vehicle (bottoming out)

1.0 Maximum threshold

Discussion: Worked Example

Posted speed limit: 60km/h

Advisory speed at the ramp: 40km/h.

Dimensions of the ramp: 100mm high and 2.0m long (1:20 grade).

Figure B1: Ramp profile

Vertical speed and vertical acceleration of a vehicle traversing the ramp at 40km/h can be calculated from Equation B1 and B2 respectively.

Vertical speed (Vvert) = 𝐻𝑉3.6𝐿

m/s B1

Vertical acceleration = 𝑉𝑣𝑒𝑟𝑡

�1.8𝐿𝑉 �9.81

𝑔 m/𝑠2 B2

Where,

H = Height of the raised platform (m)

L = Length of the sloped section (m)

V = Comfortable (advisory) speed (km/h)

g = Acceleration due to gravity (9.81 m/𝑠2)

Table B2. Vertical acceleration of the proposed ramp profile at different speeds

Speed (km/h) Vertical

acceleration (m/s2)

Driver perception

30 0.35 g Comfortable

40 0.63 g Comfortable

Maximum Speed / Discomfort

50 0.98 g Discomfort and vehicle damage

60 1.42 g Excessive discomfort

Conclusion: If motorists approaching the ramp at 60km/h continue without slowing down to advisory speed (40km/h), occupants of the vehicle experience excessive discomfort. It is expected motorists will slow down to 40km/h or below to reduce the level of discomfort thus reducing the severity of side impacts.



Appendix C – Typical Case Study Below is an example of the placement of RSP at an intersection (urban arterial) which highlights important features to consider when intersection utilising raised safety platforms.

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