Clear Zone Effectiveness and Crash Risk - Midson …

1 1 Keith MidsonClear Zone Effectiv eness and Crash RiskClear Zone Effectiveness and Crash RiskAuthorKeith MidsonBE MTraffic MTransport MITE MIEAust C PEngManager Transportation, TasmaniaGHD Pty Ltd2 Salamanca SquareHobart T AS +61 3 6210 06492 Keith MidsonClear Zone Effectiv eness and Crash RiskAbstractT he provision of an adequate Clear zone width is an integral consideration of any road design. There area number of references that are used to determine the appropriate Clear zone width for a given set ofcircumstances in both Australia and overseas. This paper provides an overview and comparisonbetween various key references on Clear zones , as well as providing a background on some of thefundamental principles and theories behind Clear zone undertook a study for VicRoads that reviewed over 30 road links acro ss metropolitan Melbournewith varying functional classifications, speed limits and Clear zone widths.

2 T he run-off-road Crash rateswere asse ssed for each road link and the resultscompared across several road categories. T hevariance from the VicRoads Clear zone guidelines was compared to the actual Clear zone provision andthe road safety performance was critically asse ssed. T his paper presents the key findings from the AuthorsKeith MidsonKeith is a traffic engineer and transport planner with thirteen years experience in local government andconsulting. He is currently Manager T ransportation with GHD in the Tasmanian Operating Centre. Keithis also an Honorary Associate with the University of T asmania and lectures T ransportation Engineeringon a part-time basis. He has a Master of T raffic and Master of T ransport with Monash University and hasworked on large and small scale projects throughout Australia and the Middle East. He is currently theSecretary on the Executive Board of the Institute of T ransportation Engineers, Australia/ New has a strong background in road safety, and has been involved in numerous projects including roadsafety strategies, road safety audits, counter-measure design, road safety investigations, road safetyresearch, Crash analysis, Crash investigation expert witness and transport studies involving a high degreeof road safety GregorDaniel is anexperienced T raffic Engineer and T ransport Planner who has worked in consulting, localgovernment and secondments at public transport operators and government land developers, where hegained practical and technical expertise in this field.

3 Daniel s key areas of interest include road safety,su stainable mobility planning and general traffic has a strong road safety background, with qualifications in road safety auditing and involvement inschemes such as traffic management for large infrastructure projects; implementation of reduced urbanspeed limits; pedestrianisation within activity centres, and a variety of road safety GuyNicole recently started with GHD as a graduate, where she has worked on a variety of transport planningand road safety projects. On this project, Nicole assisted with much of the data collection, analysis MidsonClear Zone Effectiv eness and Crash were engaged by VicRoads to investigate an outcome-based approach to determining appropriateclear zones on a case-by-case basis, for use in Victoria. T his study was commissioned in conjunctionwith three similar studies undertaken by Hyder, Monash University Accident Research Centre (MUARC)and ARRB Group, although it is noted that vastly alternative approaches were adopted by eachconsulting firm.

4 The various studies were to investigate an approach to determining Outcome BasedClear Zone Requirements , with a view to further develop a preferred he project originated following recommendations to investigate the traditional approach of theapplication of Clear zones following a Coronial Inquest. It is understood that the Parliamentary RoadSafety Committee (PRSC) supports a more conservative safety approach than that accepted for manyyears through the application of the various hrough this project,GHD have defined Outcome-based Clear Zone Guidelines as defining apotential Crash risk for a provided Clear zone on a given road classification and speed from the traditional chart based approach where a recommended Clear zone is defined byrelevant guidelines that are not always achievable for various reasons. In this way, a more educatedunderstanding of the type of Clear zone that should be provided for a given set ofparameters such asroad classification, speed limit and terrain can be obtained that provides a defined Crash risk tested a general approach to investigating the application of Clear zones , but it must beemphasised that the findings of thisstudy were not conclusive, but suggested that an alternativeapproach may be s approach to the study involved the application of an evidence based approach to investigating theeffect of Clear zone widths on run-off-the-road single vehicle Crash rates, along with a comprehensivereview of current Clear zone guidelines currently in practice in Australia and he key findings of this report were as follows: Overview of Clear zone guidelines literature review; Run-off-the-road Crash risk increases with increasing traffic volume (exposure measure).

5 Run-off-the-road Crash risk increases with decreasing Clear zone width (except for Activity Centres);and An outcome-based Clear zone approach is possible, by categorising risk profiles for road types andspeed limits. It is possible to obtain an understanding of run-off-the-road Crash risk by definingclear zone width. Then an assessment of the road design (or existing road profile) will determinethe likelihood of a his report recommends that further investigation be undertaken, including to determine the Crash risk forhigher speed roads (100km/h and 110km/h) with a higher sample rate of Victorian , the approach adopted as part of this investigation has the potentialto be very insightful, howeverit is recognised that a much larger sample of road lengths is required to produce findings of MidsonClear Zone Effectiv eness and Crash ApproachIn order to have an evidence based approach to the application of Clear zone widths for a rangeof roadtypes, the Crash history for a selection of roads with varying Clear zone widths, road classification, speedzones and other factors have been investigated to determine their significance in single vehicle run-off-the-road Crash , the approach that has been adopted by GHD includes the following key steps: Review of existing available literature and research; Based on the review of available literature and research, establish suitable objectives for thedevelopment of Outcome-based Clear Zone Guidelines.

6 Based on the project team s experience, identify features that are key factors in run-off-the-roadtype crashes; Select a small sample of road lengths in metropolitan Melbourne to test for key factors in run-off-the-road crashes and to verify an evidence based approach to identifying outcome-based clearzone guidelines; Visit each selected road length to establish existing conditions; Undertake Crash analysis for each road length (using CrashStats) to identify Crash trends for allcrash types and specifically run-off-the-road crashes; Report on the findings of the approach adopted and its suitability to identify Outcome-based ClearZone total, 25 road lengths from across Melbourne with varying features were selected, with at least fourroad lengths in each category. Each site selected was visited to record the typical and minimum offset(in metres) to any existing roadside hazards along the length as well as other information such as speedzone, kerb type, adjoining land use, road surface, horizontal geometry, etc.

7 T wo-way traffic volume datafor each road length was estimated from the strategic Melbourne Integrates T ransport Model (MITM),and accordingly, the traffic volume data is a broad estimate road sections and theirassociated he road lengths selected in this study are not considered to be fully representative of all VictorianRoads. Given the preliminary nature of this investigation project and the limited resources available toundertake site inspections, only sites within Melbourne have been selected for analysis. Accordingly, Rural Highways or Rural Roads have not been asse ssed as part of this investigation. It isrecommended that this form part of a future piece of work, however it is acknowledged that the existingclear zone guidelines are more likely to be applicable in rural highway MidsonClear Zone Effectiv eness and Crash ReviewT o enable a greater understanding of Clear - zones and theapplication of Clear zone widths for variousfunctional road designs used within other states of Australia and other countries around the world aliterature review was he Literature review included the following documents: VicRoads Guidelines Road Design Guidelines; Austroads Guidelines; Austroads Rural Road Design Guide; Austroads Urban Road Design Guide.

8 Note The Austroads Guide to Road Design Part 6 is currently in preparation, this guide is believedto cover Road Safety and contain a section on Clear zones , this may update the Clear zoneguidelines within both the Urban and Rural Road Design Guides Interstate Practice; Road Design Guidelines, Section 3: Road Cross Section (NSW); Main Roads Western Australia: Asse ssment of Roadside Hazards (WA); Chapter 8 Safety Barriers and Roadside Furniture (Department of Main Roads Road Planning andDesign Manual, QLD); Road Hazard Management Guide (Department of Infrastructure, Energy and Resources, TAS); Overseas Practice/Research; United States AASHT O; British Columbia Ministry of T ransportation and Highways T echnical Bulletin: Clear ZoneStandards; New Zealand T ransit New Zealand: State Highway Geometric Design Manual, Section 6: CrossSection; Europe European Best Practice for Roadside Design: Guidelines for Roadside Infrastructure onNew and Existing Roads (RISER);T he regions (Australian states and other countries) incorporated within the literature review revealed thatthe Clear zone guidelines for the regions were based upon either theAustroads Urban and Rural DesignGuidelines or AASHT O, or RT A NSW Road Design able1summarises the guidelines thateach region bases the Clear zone widths upon and the document that this is outlined for each state MidsonClear Zone Effectiv eness and Crash RiskTable1 Summary of Guidelines Used and Document NameState/CountryGuidelines Usedfor Clear zonesGuidelinesUsed forSafetyBarriersDocument NameDocument DateVictoriaAustRoadsAustRoadsVicRoads RoadDesignGuidelines CrossSection; zones & SafetyBarriers2002 New South WalesNSW RT ART A NSW RoadDesignGuidelines,Section 3 RoadCross Section.

9 Clear Zones1999 South AustraliaAustroads Ruraland Urban DesignGuidesAustroadsRural andUrban DesignGuides andGovernment ofSouthAustralia-Department ofT ransport,Energy andInfrastructureGuide toselection ofsafety AustraliaAustRoadsAustRoadsMain RoadsWesternAustralia:Assessment ofRoadsideHazards2007 QueenslandAASHT OAS/NZS3845:1999 Road SafetyBarrierSystems andthe NationalCooperativeHighwayResearchProgra mDepartment ofMain RoadsRoad Planningand DesignManual: Chapter8 Safety barriersand roadsidefurniture20057 Keith MidsonClear Zone Effectiv eness and Crash RiskState/CountryGuidelines Usedfor Clear zonesGuidelinesUsed forSafetyBarriersDocument NameDocument DateT asmaniaAustRoadsAS/NZS3845:1999 Road SafetyBarrierSystemsRoad HazardManagementGuideunknownNorthern TerritoryAustRoads-No responsereceived-United StatesAASHT O---British ColumbiaBased uponAASHT O but theactual Clear zonewidths are slightlydifferent-Ministry ofT ransportationand HighwaysT echnicalBulletin: ClearZone Standards1996 New ZealandAASHT O-T ransit NewZealand: StateHighwaygeometric designmanual, section6-Cross section2002 Europe--European BestPractice forRoadside Design.

10 Guidelines forRoadsideInfrastructure onNew and ExistingRoads20058 Keith MidsonClear Zone Effectiv eness and Crash RiskT he main objectives that have been identified within a number of the guidelines reviewed are ObjectivesName ofDocumentDateOrganisationObjectivesUrba n / RuralRoad DesignGuide2003 AustRoadsThe Clear zone is a compromise between the recoveryarea for every errant vehicle, the cost of providing thatarea and the probability of an errant vehicleencountering ahazard. Ideally the Clear zone should bekept free from non-frangible hazards where economicallypossible; alternatively, vehicles should be protected fromhazards within the Clear forSafer EuropeanRoads (RISER)Dupre G &Bisson D2003 RISERIf the goal of the safety zone is to eliminate impacts withobjects for impact speeds above 40 km/h, then thelateral distance of the safety zone must accommodatethe motions of the vehicles until this speed is HighwayGeometricDesign Manual,Section 6T ransit NewZealandAbout 80 percent of vehicles that run-off-the-road toregain control with minimum da mage to both vehiclesand occupantsShoulder, verge and batter design must ensure a clearzone, which will allow an errant vehicle to traverse thisarea with minimum damage to itself and ORoadsideDesign AASHT ORoadside designGuide.