Effectiveness of Road Safety Engineering Treatments

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AP-R422-12

AUSTROADS RESEARCH REPORT

Effectiveness of Road Safety

Engineering Treatments


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Effectiveness of Road Safety Engineering Treatments


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Published November 2012

Austroads Ltd 2012

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


ISBN 978-1-921991-60-8

Austroads Project No. ST1571

Austroads Publication No. AP-R422-12

Project Manager

Maurice Cammack, Main Roads WA

Prepared by

Blair Turner, Lisa Steinmetz, Adrian Lim, Karen WalshARRB Group

Published by Austroads LtdLevel 9, Robell House287 Elizabeth Street

Sydney NSW 2000 AustraliaPhone: +61 2 9264 7088Fax: +61 2 9264 1657

Email:[email protected]

Austroads believes this publication to be correct at the time of printing and does not acceptresponsibility 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]:[email protected]:[email protected]:[email protected]


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About Aust roads

Austroads purpose is to:

promote improved Australian and New Zealand transport outcomes

provide expert technical input to national policy development on road and road transportissues

promote improved practice and capability by road agencies.

promote consistency in road and road agency operations.

Austroads membership comprises the six state and two territory road transport and trafficauthorities, the Commonwealth Department of Infrastructure and Transport, the Australian LocalGovernment Association, and NZ Transport Agency. Austroads is governed by a Board consistingof the chief executive officer (or an alternative senior executive officer) of each of its elevenmember organisations:

Roads and Maritime Services New South Wales

Roads Corporation Victoria Department of Transport and Main Roads Queensland

Main Roads Western Australia

Department of Planning, Transport and Infrastructure South Australia

Department of Infrastructure, Energy and Resources Tasmania

Department of Transport Northern Territory

Department of Territory and Municipal Services Australian Capital Territory

Commonwealth Department of Infrastructure and Transport

Australian Local Government Association New Zealand Transport Agency.

The success of Austroads is derived from the collaboration of member organisations and others inthe road industry. It aims to be the Australasian leader in providing high quality information, adviceand fostering research in the road transport sector.


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CONTENTS

1 INTRODUCTION ................................................................................................................... 12 METHOD ............................................................................................................................... 22.1 Identifying Gaps in Knowledge ............................................................................................... 22.2 Filling the Gaps Knowledge ................................................................................................... 22.3 Selected Issues ..................................................................................................................... 22.4 Determining Treatment Effectiveness .................................................................................... 33 REVIEW OF LITERATURE ON CRASH TREATMENT EFFECTIVENESS ........................... 54 DISCUSSION AND RECOMMENDATIONS ........................................................................ 14REFERENCES ............................................................................................................................. 15APPENDIX A PRIORITISING GAPS IN KNOWLEDGE ................................................. 16APPENDIX B REVISIONS TO TREATMENT EFFECTIVENESS FIGURES ................... 19APPENDIX C SUMMARY OF RESEARCH FOR PRIORITY TREATMENTS ................. 25C.1 Guide Posts ......................................................................................................................... 26C.2 Chevron Alignment Markers ................................................................................................. 29C.3 Pavement Markings ............................................................................................................. 31

C.3.1 Provision of Edge Lines .......................................................................................... 31C.3.2 Provision of Centrelines ......................................................................................... 33C.3.3 Provision of Centreline and Edge Line ................................................................... 34

C.4 Profile Line Marking ............................................................................................................. 37C.4.1 Profile Edge Lining, Edge Line (Shoulder) Rumble Strip, or Shoulder Grooving ..... 37C.4.2

Profile Centre Lining, Centreline Rumble Strip ....................................................... 40

C.5 Signs Regulatory .............................................................................................................. 43

C.5.1 General: Regulatory Signs at Intersections ............................................................ 45C.5.2 Stop Signs at Three-leg Intersections ..................................................................... 45C.5.3 Stop Signs at Four-leg Intersections ....................................................................... 46C.5.4 Four-way Stop Signs .............................................................................................. 46C.5.5 Give-way Signs ...................................................................................................... 46C.5.6 Stop Sign to Give-way Sign .................................................................................... 46C.5.7 Give-way Sign to Stop Sign .................................................................................... 47C.5.8 U-turn and Right-turn Ban ...................................................................................... 47

C.6 Traffic Signals ...................................................................................................................... 48C.6.1 New Signals ........................................................................................................... 48C.6.2 Effect of Turn Phases ............................................................................................. 51C.7 Signal Visibility ..................................................................................................................... 56

C.8 Channelisation at Intersections Splitter and Median Islands .............................................. 59C.8.1 General .................................................................................................................. 60C.8.2 Splitter Islands........................................................................................................ 60C.8.3 Median Islands ....................................................................................................... 60

C.9 Grade Separated Intersections ............................................................................................ 62C.10 Right-turn Lane Provision..................................................................................................... 64

C.10.1 All Locations ........................................................................................................... 69C.10.2 Signals ................................................................................................................... 69C.10.3 Unsignalised Intersections ..................................................................................... 69C.10.4 Rural ...................................................................................................................... 70


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C.10.5 Urban ..................................................................................................................... 70C.10.6 Painted and Physical .............................................................................................. 71C.10.7 X and T-intersections ............................................................................................. 71

C.11 Extend Right-turn Lane ........................................................................................................ 74C.12

Left-turn Lane Provision ....................................................................................................... 76

C.13 Lane Width in Tunnels ......................................................................................................... 79C.14 Overtaking Lanes ................................................................................................................. 80C.15 Superelevation ..................................................................................................................... 83C.16 Impact Attenuators ............................................................................................................... 86C.17 Signs Advisory .................................................................................................................. 89

C.17.1 Curve Warning Signs ............................................................................................. 89C.17.2 Speed Advisory Signs ............................................................................................ 90

C.18 Pedestrian Treatments ......................................................................................................... 92C.18.1 Pedestrian Fencing and Barriers ............................................................................ 92C.18.2 Improved Lighting ................................................................................................... 92C.18.3 Marked Crossings .................................................................................................. 93C.18.4 Pedestrian Overpasses .......................................................................................... 94C.18.5 Pedestrian Signals ................................................................................................. 95C.18.6 Refuges.................................................................................................................. 96C.18.7 Roundabouts .......................................................................................................... 97C.18.8 Raised Pedestrian/Wombat Crossings ................................................................... 97

C.19Transverse Rumble Strips.................................................................................................. 101C.20 Street Closure .................................................................................................................... 103C.21 Street Lighting .................................................................................................................... 105

C.21.1 New Lighting All Sites ........................................................................................ 109C.21.2 New Lighting Intersections ................................................................................ 109C.21.3 New Lighting Mid-blocks ................................................................................... 109C.21.4 New Lighting Rural ............................................................................................ 109C.21.5 New Lighting Rural Intersections ....................................................................... 109C.21.6 New Lighting Urban ........................................................................................... 109C.21.7 New Lighting Urban Intersections ...................................................................... 109C.21.8 New Lighting Motorway Freeway Interchanges ................................................. 109C.21.9 Railway Crossings ................................................................................................ 109C.21.10 Upgrade Existing Lighting .................................................................................... 110C.21.11 Effect on Different Crash Types and Severities .................................................... 110C.21.12 Time of Day .......................................................................................................... 110


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TABLES

Table 3.1: Summary of treatment effectiveness ........................................................................ 6


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SUMMARY

A reliable knowledge base about the effectiveness of different road safety engineering treatmentsallows informed decisions for the development of future road safety programs. This information isused to allocate resources to the most cost-effective projects (i.e. ones that will reduce casualtiesthe most per dollar spent). Inaccurate information on treatment effect may lead to inefficient use oflimited resources. The current project aims to address this issue and to provide updated advice onthe road safety benefit of engineering treatments, based on literature reviews. Previous Austroadsresearch has identified that there is a lack of reliable information regarding the effectiveness ofdifferent road safety engineering treatments.

During the first stage of this project, a number of treatments or road safety features for which theknowledge base was inadequate were identified. The assessment was based on literature reviewsas well as stakeholder priorities. Given the large number of gaps, and the time and budgetavailable for this project, the knowledge gaps were prioritised.

A summary of the crash reduction effects for each of these treatments is provided, along with anassessment of the level of confidence in the figure (based on factors such as consistency of resultsfrom various studies and number of studies). Where possible, information on the crash reductionfor different severity outcomes and crash types is provided. However, information on these factorsis relatively scarce.

The project has identified crash effectiveness for 57 treatment types and 126 crash effectivenessvalues have been derived for these. Compared to an earlier study on this topic (Austroads 2010a),there is now more information available on treatment effectiveness (126 values compared to 104).

The project has also led to an increased level of confidence in knowledge about treatments; overhalf of the values are now allocated a medium or high level of confidence.

Although this project has improved the reliability of information on the effectiveness of treatments,a number of knowledge gaps remain that can be filled by further reviews of literature andexperimentation. During the course of this project, links were developed with an OECD initiative toaddress crash reduction effectiveness of different treatments. This initiative has led to theestablishment of an international collaboration to improve information on the crash reductioneffectiveness of treatments. There is great merit in Australian and New Zealand road safetyprofessionals contributing to the international collaboration once key gaps have been identified andprioritised by the international OECD group.

ACKNOWLEDGEMENTS

The authors would also like to acknowledge the input of the project steering group. This group ismade up of representatives from Australian road agencies, the NZ Transport Agency, the FederalDepartment of Infrastructure and Transport and AAA/AusRAP. In addition, the authors would alsolike to acknowledge the input of the Safety Task Force who provided comments on the document.


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1 INTRODUCTION

Previous Austroads research (Austroads 2010a) identified that there was a lack of reliableinformation regarding the effectiveness of different road safety engineering treatments. The

effectiveness relates to the expected reduction in crashes from the use of treatments in differentcircumstances. The effectiveness of a treatment can be expressed as a Crash Modification Factor(CMF). This represents the relative change in crash frequency due to a specific change in theroad or its immediate environment (Austroads 2012, p49). Effectiveness in Australia and NewZealand has traditionally been presented using Crash Reduction Factors (CRFs), which presentsthe expected percentage reduction in crashes. The term CMF is now used more widely overseas,although both terms are used in this current report1. This information is used to allocate resourcesto the most cost-effective projects (i.e. ones that will reduce casualties the most per dollar spent).Inaccurate information on treatment effect may lead to inefficient use of limited resources.

This work is one component of a large program of research. The Austroads National RiskAssessment Model project has three main objectives. The first is the development of a risk

assessment model, intended to be used nationally as a way of identifying crash risk. The secondtask involves the development of a national program for risk assessment with associatedguidelines. A third task involves improving information on the crash reduction effectiveness ofvarious road safety treatments. This included the development of a stand-alone report on astandard approach for evaluation of treatment effectiveness for adoption by road authorities. Thiswork has been published asAn Introductory Guide for Evaluating Effectiveness of Road SafetyTreatments (Austroads 2012). An associated task, and the subject of this report, involvesimproving knowledge on the road safety benefit of engineering treatments.

During the first stage of this project, treatments or road safety features were identified for whichthere were significant gaps in knowledge in terms of crash reduction effectiveness. The work alsoidentified a method for prioritising each of these issues. That process is outlined in Section 2 ofthis report. Section 3 provides information on local and international literature on each of thepriority issues identified. For completeness, the section also provides information from previouswork on this topic (Austroads 2010a) so that the sum of current knowledge on crash reductioneffectiveness for engineering treatments is provided in this report. The final section (Section4)provides concluding comments and recommendations.

1A Crash Reduction Factor indicates the expected percentage reduction in crashes following the introduction of a

treatment. A Crash Modification Factor is a proportion that represents the relative change in crash frequency due to a

specific change in the road or its immediate environment (Austroads 2012).


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2 METHOD

2.1 Identifying Gaps in Knowledge

During the first stage of this project, a number of treatments or road safety features were identifiedwhere knowledge of effectiveness in reducing crashes was not adequate. This assessment wasbased on literature reviews (Austroads 2010a, 2010b) as well as stakeholder priorities(Austroads 2009)2. For each of these issues it was identified that there was a lack of sufficientresearch on the crash reduction effect, or that the research which did exist was not considered ofsuitable quality. The identified gaps in knowledge were then prioritised. Appendix A provides theresults of this assessment.

2.2 Filling the Gaps Knowledge

Two main options were identified to address the gaps in knowledge identified above. The mostcost-effective method to address gaps in knowledge is typically through review of previously

published research. Often research will have been conducted somewhere in the world that eitheraddresses a gap in knowledge, or goes part way in addressing this gap. New studies areconducted every year, and the knowledge base is continually being updated and expanded.Although extensive literature reviews have been conducted by Austroads on many issues relatingto the effectiveness of road safety engineering treatments, there is still a need to assess any newknowledge which has been generated. It was recommended that any future research to fill gaps inknowledge reassess the available literature before embarking on empirical research.

If a gap in knowledge is deemed important enough to require further research, and adequateinformation cannot be obtained from existing literature, then a trial of the treatment will typically berequired. Austroads (2012) provides guidance on methods for evaluating the effectiveness of roadsafety treatments.

Given the cost associated with trials of treatments, and the timeframe required (three to five yearsof data is typically required after the treatment is installed), this current project focuses on literaturereview to fill gaps in knowledge.

2.3 Selected Issues

Based on the existing gaps in knowledge, and the prioritisation of the tasks, the treatments listedbelow were assessed:

In 2010/11:

grade separation of intersections

guide posts

lane width in tunnels

overtaking lanes

pavement markings edge line

pavement markings centreline

pedestrian treatments

2Engineering research priorities were identified in a previous project (Austroads 2009) via a survey of Austroads Road

Design Review Panel and Traffic Management Review Panel members.


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signs advisory

street lighting

In 2011/12:

superelevation signs regulatory

delineation continuity lines, marking in wet conditions

channelisation at intersections splitter and median islands

impact attenuators

intersection right-turn lane provision

intersection extend right-turn lane

intersection left-turn lane provision

intersection signal visibility line marking profile edge lines

street closure

traffic signals.

It should be noted that some other treatments were identified that had a higher priority than theones identified above (e.g. clear zones and vegetation). However, since extensive research iscurrently being conducted on them within Australasia, these topics were not reviewed as part ofthis project. The crash effectiveness for these will be updated once this work is complete.

The treatments assessed as part of this project (listed above) complimented previous work whichsummarised research from 2004 to 2009 (Austroads 2010a, Road Safety Engineering RiskAssessment: Part 6: Crash Reduction Factors).

2.4 Determining Treatment Effect iveness

A literature review was conducted for each of the topics listed above. Given the large number oftopics, and the limited time and budget available for this task, each review was limited in scope andcould not be considered exhaustive. The main focus was on recent research since 1999, and onresearch conducted in Australia and New Zealand. However, other key references have also beenassessed and included where relevant. Only research that contained information about the crashreduction benefit from treatments was included in the review, and this greatly reduced the numberof relevant publications.

Much of the research presented crash reductions for all crash severities (including propertydamage only). In many cases, treatment effectiveness for casualty crashes was also available.Where information was available, effectiveness values were based on casualty crashes.

Often for any one issue, a variety of treatment effectiveness values were identified. In general, anaverage crash reduction value was taken across all studies that were considered methodologicallyrobust. It would have been preferable to use a weighted average based on robustness (suchprocedures exist), however due to limited budget a more simplistic approach was taken. Outlierswere often excluded, however they were considered on a case by case basis. In some cases,logic checks were used to help refine a figure.


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Given the limited budget available for this work, a qualitative indication on the level of confidencefor each of the factors provided was estimated. This was based on the number of studies thatprovide crash reduction information, the consistency of the results, methodological robustness, theage of the research, and the country in which the research was conducted. For instance, where

four or more studies were available, each of which provided reasonably consistent results and hadrobust methodologies, a high level of confidence was assumed. This same approach was used inAustroads (2010a).

Section 3 provides a summary of the results from a review of literature on each of the topics listedas high priority.


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3 REVIEW OF LITERATURE ON CRASH TREATMENTEFFECTIVENESS

Table 3.1presents a consolidated summary of treatment effectiveness for a range of treatments,expressed as Crash Reduction Factors (CRFs) and Crash Modification Factors (CMFs). Eachfactor has been rounded (to the nearest 5%). The results have been collated from previous work(Austroads 2010a, which summarised research from 2004 to 2009) as well as this current project(2010/11 and 2011/12). Appendix B provides a summary of treatment effectiveness values thathave been updated since the completion ofRoad Safety Engineering Risk Assessment: Part 6:Crash Reduction Factors (Austroads 2010a). Details of the research conducted in 2010/11 and2011/12, including the literature assessed can be found in Appendix C. Details of research fromearlier work (up to 2008/09) can be found in the appendices to Austroads (2010a).

It is recognised that the effectiveness of treatments on different levels of severity is also of interest.This is particularly relevant in the Safe System context where there is a focus on reduction in fatal

and serious injury crash outcomes. There is also interest in quantifying the effect of treatments ondifferent crash types (e.g. head-on). Where this information is available, this is also presented inAppendix C, and in some cases, where the information is robust enough, also in Table 3.1.However, much of the research does not provide a breakdown by severity or crash type, andwhere information does exist it is often based on very small sample sizes and so is quite variable.In addition, some research (e.g. Hauer 2006 & 2009) indicates that it is not technically possible toaccurately determine changes in severity due to the frequency-severity indeterminacy. Thisstates that due to under-reporting of crashes it is not possible to determine whether the frequencyof crashes has reduced, or whether there has been a transference to higher or lower levels ofseverity.

Table 3.1also provides a measure of confidence in the factors provided. As discussed in

Section 2.3, this is a qualitative measure that is based on the number of studies that provide crashreduction information, the consistency of the results, methodological robustness, the age of theresearch, and the country in which the research was conducted.

An indication of the year in which a treatment type was assessed is also provided in Table 3.1.This is of interest as the amount of research on crash effectiveness has increased in recent years.In some cases, new research merely validates that of older studies on the same topic. In othercases, the new research can significantly change the expected crash reduction effectiveness(especially when there was previously a high degree of uncertainty). This information will alsoassist with planning and prioritisation of tasks for investigation in the future.

Note that the crash reduction figures provided for pedestrian treatments are given for changes in

pedestrian casualties only. Little information exists for these treatments on changes to all casualtycrashes. Similarly, reductions for street lighting relate only to changes in night-time casualties.Some information does exist on the effect of street lighting at all times of the day, but this was notcomprehensive enough to produce a separate factor.

Although this report is primarily concerned with road safety engineering treatments, someinformation is provided on the safety implications of changing road design elements (e.g.superelevation). Further information on the safety implications of road design can be found in aseparate report (Austroads 2010b).


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For a number of treatments that were reviewed, treatment effectiveness was unable to bedetermined. These included:

Delineation treatments: continuity lines, provision of wide edge lines, marking in wetconditions, provision of word and symbol pavement markings, transverse rumble strips (at

curves, railway level crossings and intersection approaches). Intersection treatments: extending right-turn lanes.

Pedestrian treatments: installation of pedestrian signals, installation of a marked pedestriancrossing, converting marked pedestrian crossing to signals.

Traffic management treatments: closing a street.

The review identified some evidence for a number of additional treatments. Although thisinformation is of interest (and summarised in Appendix C), there was insufficient evidence todetermine the extent of treatment effectiveness (e.g. provision of edge lines at curves, addition ofyellow reflective tape to signal heads, and channelisation in rural environments). In such cases,

the relevant appendix often includes a discussion indicating that safety benefits are likely to beassociated with such treatments, although there was insufficient evidence to gauge treatmenteffectiveness during this project.

Table 3.1: Summary of treatment effectiveness

Treatment Environmenttype

Crash r eductionfactor

Crashmodification

factor

Confidence Year mostrecently

assessed

Referencelocation

Delineation treatments

Install guide posts All 5% 0.95 Low 2010/11 Appendix C.1

Install RaisedReflective

PavementMarkers (RRPMs)

All 5% 0.95 Medium 2008/09 Austroads 2010a

Install chevronalignmentmarkers

Horizontal curves 25% 0.75 Low 2010/11 Appendix C.2

Pavementmarkings

Provide edge line 10% 0.9 Low 2010/11 Appendix C.3.1

Provide centreline 20% 0.8 Low 2010/11 Appendix C.3.2

Provide combinededge andcentreline

30% 0.7 Low 2010/11 Appendix C.3.3

Provide paintedspeed limits

0% 1.0 Low 2008/09 Austroads 2010a

Profile linemarking

Provide profileedge lines

20% (all) 0.80 (all) Medium 2011/12 Appendix C.4.1

40%(run-off-road)

0.6 (run-off-road) Low

Provide profilecentreline

15% (all) 0.85 (all) Medium 2011/12 Appendix C.4.2

30% (head-on) 0.70 (head-on) Low


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Crashmodification

factor


assessed

Referencelocation

Intersection treatments

Signs regulatory Install stop sign atT-intersection

15% 0.85 Low 2011/12 Appendix C.5.2

Install stop sign atX-intersection

30% 0.7 Medium 2011/12 Appendix C.5.3

Install four-waystop sign atX-intersection

60% 0.40 Low 2011/12 Appendix C.5.4

Install give-waysign allintersections

25% 0.75 Low 2011/12 Appendix C.5.5

Install right-turnban, or U-turnand right-turn ban


Traffic signals Install trafficsignals

30% 0.7 Low 2011/12 Appendix C.6.1

Provision of fullycontrolled right-turns

35% (all casualty) 0.65 Medium 2011/12 Appendix C.6.2

60% (rightthrough)

0.40 Low

45% (adjacentdirection)

0.55 Low

Provision ofpartially controlledright-turns

10% 0.9 Low 2011/12 Appendix C.6.2

Change partialcontrol to fully

controlledright-turns

70% 0.3 Low 2011/12 Appendix C.6.2

Linked signals Linking of existingsignals

15% 0.85 Medium 2008/09 Austroads 2010a

Signal visibility Replace apedestal mountwith mast armmount signal

35% 0.65 Low 2011/12 Appendix C.7

Increase lens sizeto twelve inches

5% 0.95 Low 2011/12 Appendix C.7

Provide additionalsignal head

20% 0.8 Medium 2011/12 Appendix C.7

Roundabouts Install roundabout rural

70% 0.3 High

2008/09

Austroads 2010a

Install roundabout urban

55% 0.45 Medium Austroads 2010a

Install roundabout allenvironments

70% (all) 0.3 (all) High Austroads 2010a

60%(pedestrians)

0.4 (pedestrians) Low 2010/11 Appendix C.18.7


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Crashmodification

factor


assessed

Referencelocation

Roundabout single versus

multilane

All roundabouts lower risk for

single lanecompared withmultilane (notethis decision isusually not madebased on safety,but rather oncapacity)


Channelisation atintersections splitter andmedian islands

Install generalchannelisation

30% 0.70 Low 2011/12 Appendix C.8.1

Install splitterislands general


Install splitter

islands urban


Install mountablemedian

15% 0.85 Low 2011/12 Appendix C.8.3

Installnon-mountablemedian

25% 0.75 Low 2011/12 Appendix C.8.3

Grade separationof intersections

X-intersection 55% 0.45 High 2010/11 Appendix C.9

Y-intersection 20% 0.8 Medium 2010/11 Appendix C.9

Install right-turnlane

Install right-turnlane general


Install right-turnlane signalised

intersection


Install right-turnlane unsignalisedintersection


Install right-turnlane ruralunsignalisedT-intersections

40% 0.6 Low 2011/12 Appendix C.10.4

Install right-turnlane ruralunsignalisedX-intersections


Install right-turnlane urban:general

30% 0.7 Low 2011/12 Appendix C.10.5

Install right-turnlane urbanunsignalisedT-intersections

35% 0.65 Low 2011/12 Appendix C.10.5

Install right-turnlane urbansignalisedT-intersections

5% 0.95 Low 2011/12 Appendix C.10.5


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Crashmodification

factor


assessed

Referencelocation

Install right-turnlane (continued)

Install right-turnlane urban

unsignalisedX-intersections

30% 0.7 Low 2011/12 Appendix C.10.5

Install right-turnlane urbansignalisedX-intersections

10% 0.9 Low 2011/12 Appendix C.10.5

Install right-turnlane painted

30% 0.70 High 2011/12 Appendix C.10.6

Install right-turnlane physical

35% 0.65 Low 2011/12 Appendix C.10.6

Install left-turn lane All 20% 0.80 Low 2011/12 Appendix C.12

Staggered

junctions

With minor road

traffic < 15% ofmain road

35% 0.65 Low 2008/09 Austroads 2010a

With minor roadtraffic 1530% ofmain road

25% 0.75 Low Austroads 2010a

With minor roadtraffic > 30% ofmain road

35% 0.65 Low Austroads 2010a

Railway level crossing treatments

From nothing tosignage

All 25% 0.75 Low 2008/09 Austroads 2010a

From signage to

lights and bells


From lights andbells to barriers


From signage tobarriers


Improve sightdistance


Road g eometry and design treatments

Overtaking lanes All 25% 0.75 Medium 2010/11 Appendix C.14

Road resurfacingto improve skidresistance

All 35% 0.65 High 2008/09 Austroads 2010a

Sight distanceimprovements

Ruralenvironments andintersections


Improving/correctingsuperelevation

AllSD* CMFunction

< 0.01 1.00

0.01 to

< 0.02

(1.00 + 6(SD 0.01)

0.02 (1.00 + 3(SD 0.02)

*SD = Superelevation deficiency

Low 2011/12 Appendix C.15

Sealing shoulders All 30% 0.7 High 2008/09 Austroads 2010a


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Crashmodification

factor


assessed

Referencelocation

Roadside treatments

Install impactattenuators

All 50% (all casualty) 0.5 (all casualty) Medium 2011/12 AppendixC.16

All 70% (fatal) 0.30 (fatal) High

Install guardrail All 40% 0.6 High 2008/09 Austroads 2010a

Access control(note that this is arelative risk thatcompares withthe level of risk ifthere were noaccess points onan undividedroad. It does notprovide a CRF orCMF)

Open road 4-lane Relative Risk = 1+(0.02 xresidential/km+0.10 x

commercial/km+0.20 x minor junctions)x ({0.45 if median-solid or > 3 m}, 1 if

no median)

Medium 2008/09 Austroads 2010a

Open road 2-lane Relative Risk = 1+(0.01 xresidential/km+0.05 x

commercial/km+0.20 x minor junctions)x ({0.45 if median-solid or >3 m}, 1 if no

median)


Built up 4-lane Relative Risk = 1+(0.01 xresidential/km+0.08 x


no median)


Built up 2-lane Relative Risk = 1+(0.02 xresidential/km+0.10 x


no median)


Signage treatments (Advisory)

Install bridgewarning signs


Install curvewarning signs

Horizontal curves 25% 0.75 High 2010/11 Appendix C.17.1

Guidance signs All 15% 0.85 Low 2008/09 Austroads 2010a

Speed advisory All 40% 0.6 Low 2010/11 Appendix C.17.2

Vehicle activatedsigns


Variable messagesigns


Pedestrian treatments

Install fencing andbarriers

All 20%(pedestrians)

0.8 (pedestrians) Medium 2010/11 Appendix C.18.1

Improved lighting All 60% (pedestriansat night)

0.4(pedestrians at

night)

Medium 2010/11 Appendix C.18.2

Add pedestrianphase at signals



Improve signaltiming



Install pedestrianoverpass



Raised (wombat)crossing




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Crashmodification

factor


assessed

Referencelocation

Refuge All 45%(pedestrians)

0.55 (pedestrians) Medium 2010/11 Appendix C.18.6

Rest on red All 50%(pedestrians)

0.5 Low 2008/09 Austroads 2010a

Speed and enforcement treatments

Speed cameras Mobile overt 40% 0.6 Medium 2008/09 Austroads 2010a

Mobile covert urban

20%(1) 0.8 Low 2008/09 Austroads 2010a

Mobile covert rural

20%(1) 0.8 Medium 2008/09 Austroads 2010a

Fixed overt urban


Fixed overt rural 30% 0.7 Low 2008/09 Austroads 2010a

Speed changein speed limit andchange in speed

Decreases inspeed limit

2008/09 Austroads 2010a

From no previousrestriction to anyspeed limit


100 to 80 km/h 15% 0.85 Medium Austroads 2010a



All reductions inspeed limit


Increases in

speed limit2008/09 Austroads 2010a

100 to 110 km/h 25% increase 1.25 Medium Austroads 2010a

< 90 to > 90 km/h 15% increase 1.15 Medium Austroads 2010a

Any increase inspeed limit

15% increase 1.15 Medium Austroads 2010a

Change in

operating speed

and effect on

safety

Where Speeda =speed after, andSpeedb = speed

before

1 2

100%

2


All environments 20% 0.80 Medium 2008/09 Austroads 2010a

Install red lightcamera

Signalisedintersection

5% 0.95 High 2008/09 Austroads 2010a

Provide transverserumble strips

Intersections 25% 0.75 Low 2011/12 Appendix C.19


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Crashmodification

factor


assessed

Referencelocation

Traffic management treatments

Medians Painted median all environments

15%(2) 0.85 Low 2008/09 Austroads 2010a

Built median urban


Built median rural


Mediancrossovers

Convert bi- touni-directionalcrossover


Closebi-directionalcrossover


Mid-block turning

provisions

All environments 35% 0.65 Medium 2008/09 Austroads 2010a

No overtakingmarkings


Parking ban All 20% 0.8 Low 2008/09 Austroads 2010a

Parking convertangle to parallel


Street closure Internal roads 40% 0.6 Medium 2011/12 Appendix C.20

Peripheral roads 5% 0.95 Low 2011/12 Appendix C.20

Street lighting New lighting alllocations

35% (night) 0.65 (night) Medium 2010/11 Appendix C.21.1

New lighting

intersections

50% (night) 0.5 (night) High 2010/11 Appendix C.21.2

New lighting mid-block


New lighting rural intersection

30% (night) 0.7 (night) Medium 2010/11 Appendix C.21.5

New lighting urban

30% (night) 0.7 (night) Low 2010/11 Appendix C.21.6

New lighting urban intersection

30% (night) 0.7 (night) Low 2010/11 Appendix C.21.7

New lighting motorway/ freewayinterchange


New lighting railway levelcrossing


Upgrade lighting 35% (night) 0.65 (night) Medium 2010/11 Appendix C.21.10

Traffic calming All environments 20% 0.8 Medium 2008/09 Austroads 2010a


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Crashmodification

factor


assessed

Referencelocation

Work zones Increase crashrisk with presence

of road works

30% increasecompared with

when no workspresent


Minor treatmentsat work zones(e.g. pavementmarking)

15% improvementover no treatment


Major treatments(e.g. barriers,cones, markings,advancedwarning signs)

45% improvementover no treatment


1 Covert speed camera evaluations are typically conducted on an area-wide basis, so cannot be compared to overt evaluations which are conducted at or nearcamera sites.

2 Austroads 2010a provided a CRF range of 1520% for installation of a painted median. This has been rounded down to 15% to provide a single figure.Notes: Crash Reduction/Crash Modification Factors provided in this table have been rounded to the nearest 5%. Treatments assessed in 2008/09 were evaluated as part of a previous Austroads project, Road safety engineering risk assessment: Part 6: Crash Reduction

Factors (Austroads 2010a). This summarised research conducted between 2004 and 2009. Details on the studies assessed can be found in the appendices toAustroads (2010a).


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4 DISCUSSION AND RECOMMENDATIONS

Based on an extensive review of the relevant literature, crash reduction estimates have beendeveloped for 57 treatment types. In total, 126 crash reduction values have been derived for these

issues, as in some cases, information is available for different environment types (e.g. rural andurban), different crash types (e.g. all crashes and run-off-road) or different crash severities.

Despite the extensive body of research on treatment effectiveness, there is still a lack of reliableinformation on many of the safety treatments assessed in this study. However, out of the 126crash reduction values, 52% had a high or medium level of confidence. The additional workconducted through this study has increased the level of confidence in the treatment effectivenesscompared to the results obtained in an earlier study on this topic (Austroads 2010a, where 40% ofthe results had medium or high levels of confidence).

Further research is recommended for those crash reduction values that have a low level ofconfidence, or where there is no existing information. Such research will provide a higher level of

confidence in the crash reduction estimates. As identified in this report, the most cost-effectiveapproach is to conduct further reviews of literature, although it may be several years beforeadequate information exists. Alternatively, experimentation, or analysis from existing data sources(for instance, crash monitoring databases) will be required. A recommended approach toconducting evaluations using these approaches is provided in Austroads (2012). This guide alsoprovides information to help determine the robustness of evaluations already undertaken, and themethodologies that they employ.

Combinations of treatments are commonly used to address high risk sites. Very little information isavailable on the combined benefit from using more than one treatment. Previous Austroadsresearch has identified the need to assess the benefits of groups of treatments (Austroads 2012).There is a need to prioritise the most commonly used treatment combinations, and then assess the

effectiveness of these.

In addition, ARRB in association with FHWA in the United States, initiated an internationalcollaboration on the development of crash reduction values through the OECD J oint TransportResearch Centre. Involvement in the OECD collaboration has provided access to an internationalpanel of experts with extensive experience in the development of crash reduction values, andaccess to the information that they currently hold. In the longer term this will lead to astrengthened international collaboration on this topic, including the potential for joint projects to fillexisting gaps in knowledge.

Although confidence in some of the crash reductions provided is not high, these are still the bestestimates available for each type of treatment. In the absence of additional information on crashreduction based on total casualty crashes it is recommended that these figures be considered foruse by jurisdictions when calculating the expected benefits from treatments.

It is important to continue collaboration with local and international research partners, as well asupdating of information when relevant research is complete (such as current research on clearzones) to develop guidance on the effectiveness of further treatment types, as well as improvingconfidence in the values presented in this report.


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REFERENCES

Austroads 2009, Design, feasibility and application of an instrumented vehicle, AP-T145-09, Austroads,Sydney, NSW.

Austroads 2010a, Road safety engineering risk assessment: Part 6: Crash Reduction Factors, AP-T151-10,Austroads, Sydney, NSW.

Austroads 2010b, Road safety engineering risk assessment: part 1: relationships between crash risk and thestandards of geometric design elements, AP-T146/10, Austroads, Sydney, NSW.

Austroads 2012,An Introductory Guide for Evaluating Effectiveness of Road Safety Treatments,AP-R421-12, Austroads, Sydney, NSW.

Elvik, R, Hye, A, Vaa, T & Srensen, M 2009, The handbook of road safety measures, 2nd edn, EmeraldPublishing, Bingley, UK.

Hauer, E 2006, The frequency-severity indeterminacy [unreported crashes],Accident Analysis andPrevention, vol. 38, no. 1, pp.78-83.

Hauer, E 2007, Kinds of safety evaluation study, Issues in road safety evaluation workshop, 28-29 March2007, Romsey, Victoria, Monash University Accident Research Centre, Clayton, Vic.

Hauer, E 2009, Speed and safety, Transportation Research Record, no. 2103, pp.10-7.

Ogden, KW 1996, Safer roads: a guide to road safety engineering, Avebury Technical, Aldershot, UK.


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APPENDIX A PRIORITISING GAPS IN KNOWLEDGE

During the first stage of this project, a number of treatments or road safety features were identifiedwhere knowledge of effectiveness in reducing crashes was not adequate. This assessment was

based on literature reviews (Austroads 2010a, 2010b) as well as stakeholder priorities(Austroads 2009). For each of these issues it was identified that there was a lack of sufficientresearch on the crash reduction effect, or that the research which did exist was not considered ofsuitable quality.

A simple matrix was developed to help prioritise the identified gaps in knowledge, with each issuesubjectively assessed by the project team against the following criteria:

Frequency (F) How often the treatment is likely to be used: When prioritising the identifiedgaps in knowledge, common treatments were given a higher priority (for example, signs).

Cost (C) The typical cost of the treatment: It was considered that for high cost treatments,there is generally a greater need to be more certain about the safety benefit compared to a

low cost treatment. In some cases low cost treatments tend to be very widely used, forexample signs. Although the individual cost of this treatment is relatively low, the sheernumber of signs installed and maintained means that there is a high total cost from the use ofthis treatment.

Uncertainty (U) The level of uncertainty associated with the known crash reductioneffectiveness of the treatment: Hauer (2007) suggests that there are costs associated withmaking incorrect assumptions about the treatment effectiveness. The likelihood of this errorcan be calculated given the standard error and expected crash reduction.

For each of these factors a one to five scale was adopted, with one indicating a low value, and fiveindicating a high value. A qualitative approach was taken in the prioritisation of gaps in knowledge,

based on subjective assessment of each of the above factors. It was noted that a quantitativeapproach could have been adopted (involving development of a benefit-cost ratio for each of thetreatment types, allowing direct comparison between them). However, it was decided that such aquantitative approach would require a number of assumptions, and that therefore the additionalanalysis required was unlikely to produce a more robust result than the qualitative approach.

The ratings for each were then multiplied to give a total score3. Table A 1 provides the results ofthis assessment.

Table A 1: Gaps in knowledge priority matrix

Treatment Frequency (F) Cost (C) Uncertainty (U) Comments FxCxU

Channelisation at intersections splitter and median islands 2 3 4 Splitter islands mainly from one NZstudy. Median islands based on one USstudy.

24

Clear zones 5 5 5 Very high priority, but being addressedthrough ST1427.

125

Delineation continuity lines,marking in wet conditions

4 2 5 No information available. 40

Grade separation of intersections 2 5 5 Based on one study only (Elvik et al.2009). No Australasian figure available.

50

3An alternative prioritisation method was also applied whereby frequency and cost are added together before being

multiplied by uncertainty. However, the outcome from this analysis was similar to a straight multiplication of each

element hence the method was not included in this report.


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Guide posts 5 2 3 Five studies, with one from Australiaand one from NZ. Gap relates toeffectiveness on curves versusstraights.

30

Impact attenuators 3 3 3 Two US studies available, butrobustness uncertain. One Australianfigure available, but cannot trace originof this, and so therefore cannot use.

27

Intersection extend right-turn lane 2 3 4 Based on two US studies. 24

Intersection left-turn provision 3 3 3 Three studies, one from Australia. 27

Intersection red light camera 3 3 1 Delete from list adequate informationon this.

9

Intersection right-turn lane 3 3 2 Many studies on this topic, and theoverall CRF is quite reliable. Gaps inknowledge regarding different types ofintersection.

18

Intersection signal visibility 3 2 4 Only one US study available. 24

Lane width tunnels 2 4 5 No information on this topic. 40

Line marking profile edge lines 2 2 4 Gap in knowledge actually relates tocentreline markings. Only one Canadianstudy available as part of originalreview. There is now more recentliterature on this.

16

No overtaking markings 3 2 2 Four US studies available, noAustralasian study. Robustness of USstudies uncertain.

12

Overtaking lanes 3 4 3 Adequate information regardingovertaking lane provision. Gaps appear

when looking at specific lane types.

36

Parking ban 2 2 2 Seven studies assessed, but many withlow robustness. No studies fromAustralasia.

8

Parking convert angle to parallel 1 2 3 Three estimates provided (two US, Elviket al.). Estimates vary substantiallyleading to low confidence. No estimatesfrom Australasia.

6

Pavement markings centreline 5 2 3 Based on six studies, but none fromAustralasia. Also, no information on useat curves.

30

Pavement markings edge line 5 2 3 Gap in knowledge relates to provision atcurves.

30

Pavement markings words andsymbols

1 1 4 Several marking types; no Australasianstudies.

4

Pavement markings paintedspeed limits

1 1 3 Four studies, two from Australia. 3

Pedestrian crossings 5 3 5 75

Pedestrian treatment rest on red 1 1 4 One Australian study. 4

Railway crossing treatments 2 4 3 Three studies Elvik et al. and two fromAustralia. However, Australian studiesdo not provide source.

24

Signs advisory 5 3 4 Gaps in speed advisory signs, curvewarning, chevrons, animal warning.

60


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Signs regulatory 5 3 4 Gaps relating to installation of stop andgive-way signs. Although there are anumber of studies, each gives vastlydifferent results.

60

Staggered junctions 2 4 2 Currently based on Elvik et al.Australian data has been identified.

16

Street closure 1 3 5 Ogden (1996) provides an estimate, butbasis of this uncertain.

15

Street lighting 4 4 2 Gap in knowledge only appears whenlooking at very specific environments.

32

Superelevation 4 3 5 Several studies found, but none thoughtto be reliable.

60

Traffic signals 5 3 2 There are several studies on this topic,two significant ones from Australia. Onlyreally low confidence because CRFsare broken down by different types of

signal installations.

30

U-turn bans 2 1 5 One US study plus the Austroads guidewhich makes an estimate.

10

Vegetation 4 4 5 Currently being addressed in clear zoneresearch.

80

Work zones 3 3 3 Seven studies on increased risk at workzones, and results are consistent. Gapin knowledge lies in severity outcomesfrom different treatments.

27


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APPENDIX B REVISIONS TO TREATMENT EFFECTIVENESS FIGURES

Table B 1provides a comparison summary of treatment effectiveness values that have been updated since the completion ofRoad SafetyEngineering Risk Assessment: Part 6: Crash Reduction Factors (Austroads 2010a). Austroads 2010a followed the same methodology as the currentproject, and involved literature reviews of 47 treatment types for which 104 treatment effectiveness values were determined. For these, 40% of theresults had medium or high levels of confidence attributed. (Comparatively, for the current project, 126 crash reduction values were derived for 57treatment types, for which 52% had a high or medium level of confidence.)

Table B 1: Updated treatment effectiveness values

Original Crash Reduction Factors identified in Road safety engineering risk assessment: Part 6:Crash Reduction Factors(Austroads 2010a)

Revised descriptions or reductions identified in current project

Issue Environm ent type % Reduction Confidenc e Treatment type Environ ment type % Reduction Confidence

Channelisation atintersections

splitter and medianislands

Splitter island all environments 40% Low Channelisation atintersections splitterand median islands

Install general channelisation 30% Low

Install splitter islands general 30% Medium

Splitter island rural 35% Low Install splitter islands urban 35% Medium

Splitter island urban 40% Low Install mountable median 15% Low

Splitter island T-intersection 45% Low Install non-mountable median 25% Low

Splitter island X-intersection 40% Low

Median island mountable 15% Low

Median island non-mountable 25% Low

Grade separation ofintersections

All environments, grade separationof intersection

50% (all severities) Low Grade separation ofintersections

X-intersection 55% High

Y-intersection 20% Medium

Guide posts Rural 28% (night) Low Install guide posts All 5% Low

Impact attenuators All 60% Low Install impact attenuators All 50% (all casualty) Medium

All 70% (fatal) High


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Intersection right-turnlane

All environments 35% Medium Install right-turn lane Install right-turn lane general 35% Medium

At signalised intersections 35% Low Install right-turn lane signalisedintersection

30% Medium

At unsignalised intersections 35% Low Install right-turn lane unsignalisedintersection

35% Medium

Urban 30% Low Install right-turn lane rural

unsignalised T-intersections

40% Low

Rural 35% Low Install right-turn lane ruralunsignalised X-intersections

30% Medium

Painted 30% Low Install right-turn lane urbangeneral

30% Low

Protected 35% Low Install right-turn lane urbanunsignalised T-intersections

35% Low

Install right-turn lane urbansignalised T-intersections

5% Low

Install right-turn lane urbanunsignalised X-intersections

30% Low

Install right-turn lane urbansignalised X-intersections

10% Low

Install right-turn lane painted 30% High

Install right-turn lane physical 35% Low

Intersection extend

right-turn lane

All environments 15% Low Intersection extend

right-turn lane

Unknown Unknown n/a

Intersection left-turnprovision

All environments 30% Low Install left-turn lane All 20% Low


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Intersection signalvisibility

All environments 25% Low Signal visibility Replace a pedestal mount withmast arm mount signal

35% Low

Increase lens size to twelve inches 5% Low

Provide additional signal head 20% Medium

Line markings profileedge lines

Shoulder 23% Medium Profile line marking Provide profile edge lines 20% (all) Medium

40% (run-off-road) Low

Centreline 15% Low Provide profile centreline 15% (all) Medium

30% (head-on) Low

Line markings profileedge lines

Transverse Unknown n.a. Provide transverserumble strips

Intersections 25% Low

Overtaking lanes All environments 23% Medium Overtaking lanes All 25% Medium

Tack-on lane 5% Low

New alignment and passing lane 54% Low

Pavement markings Centreline 30% Low Pavement markings Provide edge line 10% Low

Edge line 20% Low Provide centreline 20% Low

Words and symbols Unknown n.a. Provide combined edge andcentreline

30% Low

Painted speed limits 0% Low Provide painted speed limits 0% Low


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Pedestrian crossings No reliable reductions determinedfor this issue

Unknown n.a. Pedestrian treatments Install fencing and barriers 20% (pedestrians) Medium

Improved lighting 60%(pedestrians at night)

Medium

Add pedestrian phase at signals 50% (pedestrians) Low

Improve signal timing 35% (pedestrians) Low

Pedestrian treatment rest on red

All 50% Low Install pedestrian overpass 85% (pedestrians) Low

Raised (wombat) crossing 20% (pedestrians) Low

Refuge 45% (pedestrians) Medium

Rest on red 50% (pedestrians) Low

Install roundabout allenvironments

60% (pedestrians) Low

Signs regulatory(intersection)

Install stop sign at T-intersection 20% Medium Signs regulatory Install stop sign at T-intersection 15% Low

Install stop sign at X-intersection 30% Medium

Install stop sign at X-intersection 35% Medium Install four-waystop sign atX-intersection

60% Low

Install give-way sign allintersections

15% Low Install give-way sign allintersections

25% Low

U-turn bans No reliable reductions determinedfor this issue

Unknown n.a. Install right-turn ban, or U-turn andright-turn ban

60% Medium

Signs regulatory(midblock)

All environments 25% Low Treatment type omitted, as not considered useful

Signs advisory Chevron warning signs allenvironments

30% Low Delineation treatments install chevrons

Horizontal curves 25% Low


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Signs advisory Advisory speed signs allenvironments

25% Low Advisory signagetreatments

Install curve warning signs 25% High

Curve warning signs allenvironments

25% Low Speed advisory 40% Low

Street closure No reliable reductions determinedfor this issue

unknown n.a. Street closure Internal roads 40% Medium

Peripheral roads 5% Low

Street lighting Install lighting midblock 40% (night) Medium Street lighting New lighting all locations 35% (night) Medium

New lighting intersections 50% (night) High

Install lighting rural 30% (night) Low New lighting mid-block 40% (night) High

New lighting rural intersection 30% (night) Medium

Install lighting rural intersection 40% (night) Medium New lighting urban 30% (night) Low

New lighting urban intersection 30% (night) Low

Install lighting urban 30% (night) Low New lighting motorway/freewayinterchange

50% (night) High

Install lighting urban intersection 20% (night) Low New lighting railway levelcrossing

60% (night) High

Upgrade lighting 35% (night) Medium

Superelevation No reliable reductions determinedfor this issue

Unknown n.a. Improving/correctingsuperelevation

All 10% Low


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Traffic signals New signals, no turn arrows metro

45% Low Traffic signals Install traffic signals 30% Low

New signals, with turn arrows metro

40% Low Provision of fully controlled right-turns

35% (all casualty) Medium

New signals, no turn arrows regional

75% Low 60% (right through) Low

45% (adjacent

direction)

Low

New signals, with turn arrows regional

35% Low Provision of partially controlledright-turns

10% Low

Change partial control to fullycontrolled right-turns

70% Low

Vegetation No reliable reductions determinedfor this issue

Unknown n.a. Treatment type omitted (topic is being covered as part of other current research)

Weather Dry weather, reduction from crashrisk in wet weather

20% Low Treatment type omitted (topic is being covered as part of other current research)


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APPENDIX C SUMMARY OF RESEARCH FOR PRIORITYTREATMENTS

This appendix presents details of the research conducted in 2010/11 and 2011/12. Each appendixincludes a tabulated summary of treatment effectiveness (generally reductions) found in theresearch. Where available, effectiveness for different levels of severity or crash types wereincluded. The main focus for the review was on recent research although in some cases olderresearch is also included. There was also a focus on research conducted in Australia and NewZealand. However, other key references have also been assessed and included where relevant.Only research that contained information about the crash reduction benefit from treatments wasincluded, which greatly reduced the number of relevant publications.

Note that throughout this appendix many of the references assessed did not contribute anyinformation to the final crash reduction factor. The references are provided for completeness, butmay also provide a useful source of additional information on each treatment type.

A discussion is included for each which presents the rationale for the treatment effectivenessvalues presented in Table 3.1. The review identified some evidence for a number of additionaltreatments (than those presented in Table 3.1) for which there was insufficient evidence todetermine the extent of treatment effectiveness (e.g. provision of edge lines at curves, addition ofyellow reflective tape to signal heads, and channelisation in rural environments). In such cases,the relevant appendix generally includes a discussion indicating that safety benefits are likely to beassociated with such treatments, although there was insufficient evidence to gauge treatmenteffectiveness during this project.


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C.1 Guide Posts

Summary of research

Study Year Country Environment/Treatment Reduction

Vincent 1978 Australia Open Corner cube showed 60% reduction in night,only 21% reduction at control

Bali et al. 1978 USA General (all sites) No treatment: 3.2943(standard error 0.511)

With centreline: 2.3473(standard error 0.114)

With centreline & post: 1.3285(standard error 0.080)

Bali et al. 1978 USA Straight sites No treatment: 3.7740(standard error 0)

With centreline: 2.2375(standard error 0.169)

With centreline & post: 1.1323

(standard error 0.071)

Bali et al. 1978 USA Curves Centreline and edge line: 2.4925(standard error 0.261)

Centreline and edge line and post: 1.9306(standard error 0)

Sanderson & Fildes 1984 Australia(Victoria)

Open Corner cube 15% decrease at night, but 21%decrease at control sites

Creasey & Agent 1985 USA Post delineators 20% reduction

LTSA 1992 NZ 3267% reduction on curves, 1518% onwhole route

Cairney 1993 Australia(Victoria)

Open Corner cube delineators (17 before, 6 after)

65% reduction

Agent, Stamatiadis &Jones

1996 USA Recommended 30% reduction in night-time


1996 USA Reported post delineators at curves 23%reduction in all; 30% at night


1996 USA Reported post delineators at tangent1628% reduction in all; 30% reduction in night


1996 USA Reported flexible delineator post 40% reductionin all

Corben et al. 1997 Australia 27% reduction, but only at one site (notsignificant). Crash costs reduced by 85%, andwere significant.

Douglas 2000 USA Two-lane roads 30% reduction for delineators on curvesDouglas 2000 UK Undivided roads 67% reduction

Douglas 2000 UK Divided roads 30% reduction

Elvik et al. 2009 International All accidents Injury accidents 7% reduction(95% CI -22; +12)

Elvik et al. 2009 International All accidents PDO 3% reduction (95% CI -27; +28)

Elvik et al. 2009 International Combined treatment ofedge line, centreline anddelineator posts

Injury accident 45% reduction(95% CI -56; -32)


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Study Year Country Environment/Treatment Reduction

AASHTO 2010 USA Installing post-mounteddelineators on ruraltwo-lane undivided roads

Injury accidents have a CMF of 1.04(caveat observed variability suggests thistreatment could result in an increase, decreaseor no change)

AASHTO 2010 USA Rural two-lane road Combined treatment

Edge lines, centrelines and guide posts

Injury crashes have a CMF of 0.55 (standarderror 0.1)

Results from older studies have not been used given that new guide post designs now exist andare likely to provide a different benefit. The study by Corben et al. is from Australia, but did notprovide a statistically significant result, although it does provide a useful direction of effect (i.e. apossible positive benefit). The Vincent review is based on older research and was also excluded.

Elvik et al. and the AASHTO provide more recent results. Elvik et al. suggests a 7% CRF for thetreatment while the AASHTO suggests there is a 4% increase in crashes (although it is observedthat due to variability, this treatment could deliver an increase, decrease, or no change in crashes).

It appears from more recent research that the benefits from using guide posts on their own mightnot be substantial (and indeed, the US research indicates a possible increase in crashes, mostlikely due to an increase in speed which has been identified in research). However, additionalassessment by Elvik et al. suggests that when used in combination with other delineationtreatments (specifically an edge and centreline) that the benefit is likely to be substantial (a 45%reduction).

Agent, Stamatiadis and J ones indicate that there is no great difference in the benefit of guide postsat curves versus straights, although the New Zealand research from LTSA indicates that benefits

are substantially greater at curves when compared to whole routes.

Given the variability of the results from the HSM, the Elvik et al. figure of a 7% reduction iscurrently recommended (rounded to 5%). The crash reductions provided by Elvik et al. arespecified as all accidents. Some of the research indicates that benefits at night are greater thanchanges in at all times of day for this treatment type, however there is insufficient information toprovide a figure.

References assessed

AASHTO 2010, Highway safety manual, 1st edn, American Association of State Highway and TransportationOfficials, Washington, DC, USA.

Agent, KR, Stamatiadis, N & J ones, S 1996, Development of accident reduction factors, report KTC-96-13,Kentucky Transportation Centre, University of Kentucky, Lexington, KY, USA.

Bali, S, Potts, R, Fee, J A, Taylor, J I & Glennon, J 1978, Cost effectiveness and safety of alternative roadwaydelineation treatments for rural two-lane highways: vol II: final report, FHWA/RD-78-51, FederalHighway Administration, Washington, DC, USA.

Cairney, P 1993, Current issues in delineation, Road and Transport Research, vol.2, no.2, pp.28-39.

Corben, B, Deery, H, Mullan, N & Dyte, D 1997, The general effectiveness of countermeasures for crashesinto fixed roadside objects, report 111, Monash University Accident Research Centre, Clayton, Vic.


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Creasey, T & Agent, KR 1985, Development of accident reduction factors, research report UKTRP-85-6,Kentucky Transportation Research Program, University of Kentucky, Lexington, KY, USA.

Douglas, J 2000, Making the delineation message clear, Roadmarking Industry Association of Australia andNew Zealand Roadmarkers Federation joint conference, 6th, 2000, Canberra, Australian Capital

Territory, Roadmarking Industry Association of Australia, Rosebud, Vic, 16 pp.

Elvik, R, Hye, A, Vaa, T & Srensen, M 2009, The handbook of road safety measures, 2nd edn, EmeraldPublishing Group, Bingley, UK.

Land Transport Safety Authority 1992, Guidelines for rural road marking and delineation, RTS 5, NewZealand Transport Agency, Wellington, NZ, viewed 14 J uly 2011,.

Montella, A 2005, Safety reviews of existing roads: a quantitative safety assessment methodology,Transportation Research Record, no. 1922, Transportation Research Board, Washington, pp. 65-72.

Sanderson, J T & Fildes, B 1984, Run-off-the-road accidents in rural areas, report TS84/6, Traffic and SafetyDepartment, Royal Automobile Club of Victoria (RACV), Melbourne, Vic.

Vincent, EN 1978, A trial installation of corner cube delineators: Calder Highway, Gisborne to Woodend,Australian Road Research, vol. 8, no. 3, pp. 38-40.


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C.2 Chevron Alignment Markers

Summary of research

Study Year Country Enviro nment/Treatment Reduction

Agent, Stamatiadis andJones

1996 USA Not specified Warning signs chevron30% average reduction all crashes(lit review three papers)

55% average reduction all crashes (statesurvey two states)

Montella 2009 Italy Divided highways, 4 lanestotal

46.3% (95% CI -171.5; 78.8). Not significant

Srinivasan et al. 2009 USA Install chevrons onhorizontal curves rural

all severities, non-intersection CMF 4%

all severities, non-intersection, head-on,run-off-road, side swipe CMF 6%

fatal/serious injury/minor injury,non-intersection CMF 16%

all severities, night, non-intersection CMF25%

all severities, night, non-intersection,head-on, run-off-road, side swipe CMF22%

AASHTO 2010 USA Installing chevron signson horizontal curvesalong urban andsuburban arterials

appears to reduce crashes of all types.However, the magnitude of the crash effect isnot certain at this time. (p 1366)

UK-MoRSE website 2010 UK Rural

Rural but with othersupporting treatments

Any environment, andwhen used with othersupporting treatments

35% reduction (95% CI -1.28; 70.87)

46% reduction (95% CI 21.95; 70.4)

50% reduction (95% CI 34.88; 64.46)

A CRF of 25% was selected based on the limited evidence available. This includes a 30%reduction from Agent, Stamatiadis and J ones, a 4% reduction from Srinivasan et al. and a 35%reduction from the UK MoRSE database. There were also non-significant findings from Montellaand AASHTO that this treatment has a positive benefit. There is a low level of confidence in thisfigure.

References assessed

AASHTO 2010, Highway safety manual, 1st edn, American Association of State Highway and TransportationOfficials, Washington, DC, USA.

Agent, KR, Stamatiadis, N & J ones, S 1996, Development of accident reduction factors, research reportKTC-96-13, Kentucky Transportation Centre, University of Kentucky, Lexington, KY, USA.

Andreassen, DC 1989, Strategies for safety problems, research report ARR 163, Australian Road ResearchBoard, Vermont South, Vic.

Andrew OBrien and Associates 2000, Managing traffic flow on urban freeways: appendix A: literaturereview, Andrew OBrien and Associates, Melbourne, Vic.


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Austroads 2009, Guide to road safety: part 8: treatment of crash locations, AGRS08/09, Austroads, Sydney,NSW.

Bureau of Transport Economics (BTE) 2001, The black spot program 1996-2002: An evaluation of the firstthree years, report no. 104, Bureau of Transport Economics (BTE), Canberra, Australia.

Creasey, T & Agent, KR 1985, Development of accident reduction factors, research report UKTRP-85-6,Kentucky Transportation Research Program, University of Kentucky, Lexington, KY, USA.

Donald, D 1997, Be warned! A review of curve warning signs and curve advisory speeds, research report304, Vermont South, Vic.

Elvik, R, Hye, A, Vaa, T & Srensen, M 2009, The handbook of road safety measures, 2nd edn, EmeraldPublishing Group, Bingley, UK.

Ewing, R 1999, Traffic calming: state of the practice, report FHWA-RD-99-135, Federal HighwayAdministration, Washington, DC, USA.

Kneebone, DC 1964, Advisory speed signs and their effect on traffic,Australian Road Research Boardconference, 2nd, 1964, Melbourne, Victoria, Australian Road Research Board, Vermont South, Vic,vol. 2, no. 1, pp. 524-41.

Kulmala, R 1994, Measuring the safety effect of road measures at junctions,Accident Analysis andPrevention, vol. 26, no. 6, pp. 781-94.

Lamm, R, Zumkeller, K & Beck, A 2001, Traffic safety: the relative effectiveness of a variety of roadmarkings and traffic control devices, Road Safety on Three Continents, 2000, Pretoria, South Africa,VTI Konferens 15A, Swedish National Road and Transport Research Institute, Linkoeping, Sweden,pp. 120-32.

Montella, A 2009, Safety evaluation of curve delineation improvements: empirical Bayes observationalbefore-and-after study, Transportation Research Record, no. 2103, Transportation Research Board,Washington, pp. 6979.

Moses, P 1987, Combating the road toll, National Local Government Engineering conference, 4th, 1987,Perth, Western Australia, Institution of Engineers Australia, Canberra, ACT, pp.70-4.

Srinivasan, R, Baek, J , Carter, D, Persaud, B, Lyon, C, Eccles, K, Gross, F, & Lefler, N 2009, Safetyevaluation of improved curve delineation, report FHWA-HRT-09-045, Federal Highway Administration,Washington, DC, viewed 13 December 2010,.

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C.3 Pavement Markings

Summary of research

C.3.1 Provision of Edge Lines


Jackson in Ogden(1996)

1981 UK 13% to 32% reduction all crashes

37% to 42% reduction night crashes

Willis, Scott and Barnesin Ogden (1996)

1984 UK Rural roads Inconclusive

Creasey & Agent 1985 USA Not specified 15% reduction total crashes

Moses in in Ogden(1996)

1986 Australia Rural highways Wide edge lining:

8% reduction all crashes

34% reduction out-of-control single vehicle

Nairn in Ogden (1996) 1987 Australia Straight roads 15% reduction straight roads

45% reduction curves

Cottrell 1987 USA Not specified 0% no effect for run-off-road crashes

County SurveyorsSociety in Ogden (1996)

1989 UK Only effective at sites that experience loss ofcontrol type crashes

Moses 1990 Australia Curves 25% reduction night time crashes

5% reduction day time crashes for failing tomake the bend crashes through addition ofRRPMs and edge lining on lower speedcurves

VicRoads 1990 Australia Curves 10% reduction delineation(does not specify type)

Miller in in Ogden (1996) 1992 USA 20% reduction (average) all crashes

Tignor in in Ogden(1996)

1993 USA 2% reduction all crashes

25% reduction run-off-road

Miller 1993 USA and others Not specified 2021% reduction average for delineation

Edge lines:

8% reduction USA nationwide

16.5% reduction Kansas

14.5% reduction Kansas

19% reduction Ohio

21% reduction Illinois

16% reduction Idaho

38% reduction Utah

60% reduction Arizona

3% reduction Michigan18% reduction East Sussex

30% reduction South Yorkshire

26% reduction Cornwall

12% reduction Northamptonshire

22% reduction Hertfordshire

27% reduction Lorraine

20% reduction Hesse

25% reduction Lower Saxony

36% reduction Centreline and edge line(where previously none)

8% reduction add edge line where alreadycentreline


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Moses 1994 Australia(Western

Australia)

Not specified 25% reduction fatal out-of-control crashes withprovision of 150 mm edge lines


1996 USA Not specified 20% reduction state survey

15% reduction lit review

15% reduction all crashes recommended

30% reduction off-road crashes

Documents

Effectiveness of Road Safety Engineering Treatments