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AccidentAnalysisandPreventionThispaperdescribesaprojectundertakentoestablishaself-explainingroads(SER)designprogrammeonexistingstreetsinanurbanarea.Themethodologyfocussedondevelopingaprocesstoidentifyfunctionalroadcategoriesanddesignsbasedonendemicroadcharacteristicstakenfromfunctionalexemplarsinthestudyarea.Thestudyareawasdividedintotwosections,onetoreceiveSERtreatmentsdesignedtomaximisevisualdifferencesbetweenroadcategories,andamatchedcontrolareatoremainuntreatedforpurposesofcomparison.TheSERdesignforlocalroadsincludedincreasedlandscapingandcommunityislandstolimitforwardvisibility,andremovalofroadmarkingstocreateavisuallydistinctroadenvironment.Incomparison,roadscategorisedascollectorsreceivedincreaseddelineation,additionofcyclelanes,andimprovedamenityforpedestrians.Speeddatacollected3monthsafterimplementationshowedasignificantreductioninvehiclespeedsonlocalroadsandincreasedhomogeneityofspeedsonbothlocalandcollectorroads.Theobjectivespeeddata,combinedwithresidents’speedchoiceratings,indicatedthattheprojectwassuccessfulincreatingtwodiscriminablydifferentroadcategories.2010ElsevierLtd.Allrightsreserved.AccidentAnalysisandPreventionThispaperdescribesaprojectundertakentoestablishaself-explainingroads(SER)designprogrammeonexistingstreetsinanurbanarea.Themethodologyfocussedondevelopingaprocesstoidentifyfunctionalroadcategoriesanddesignsbasedonendemicroadcharacteristicstakenfromfunctionalexemplarsinthestudyarea.Thestudyareawasdividedintotwosections,onetoreceiveSERtreatmentsdesignedtomaximisevisualdifferencesbetweenroadcategories,andamatchedcontrolareatoremainuntreatedforpurposesofcomparison.TheSERdesignforlocalroadsincludedincreasedlandscapingandcommunityislandstolimitforwardvisibility,andremovalofroadmarkingstocreateavisuallydistinctroadenvironment.Incomparison,roadscategorisedascollectorsreceivedincreaseddelineation,additionofcyclelanes,andimprovedamenityforpedestrians.Speeddatacollected3monthsafterimplementationshowedasignificantreductioninvehiclespeedsonlocalroadsandincreasedhomogeneityofspeedsonbothlocalandcollectorroads.Theobjectivespeeddata,combinedwithresidents’speedchoiceratings,indicatedthattheprojectwassuccessfulincreatingtwodiscriminablydifferentroadcategories.2010ElsevierLtd.Allrightsreserved.1.Introduction1.1.BackgroundChangingthevisualcharacteristicsofroadstoinfluencedriverbehaviourhascometobecalledtheself-explainingroads(SER)approach(Theeuwes,1998;TheeuwesandGodthelp,1995;Rothengatter,1999).Sometimesreferredtoassustainablesafety,asappliedintheNetherlands,thelogicbehindtheapproachistheuseofroaddesignsthatevokecorrectexpectationsanddrivingbehavioursfromroadusers(Wegmanetal.,2005;Welleretal.,2008).TheSERapproachfocusesonthethreekeyprinciplesoffunctionality,homogeneity,andpredictability(vanVlietandSchermers,2000).Inpractice,functionalityrequiresthecreationofafewwell-definedroadcategories(e.g.,throughroads,distributorroads,andaccessroads)andensuringthattheuseofaparticularroadmatchesitsintendedfunction.Multifunctionalroadsleadtocontradictorydesignrequirements,confusioninthemindsofdrivers,andincorrectexpectationsandinappropriatedrivingbehaviour.Clearlydefinedroadcategoriespromotehomogeneityintheiruseandpreventlargedifferencesinvehiclespeed,direction,andmass.Finally,predictability,orrecognisability,meanskeepingtheroaddesignandlayoutwithineachcategoryasuniformaspossibleandclearlydifferentiatedfromothercategoriessothatthefunctionofaroadiseasilyrecognisedandwillelicitthecorrectbehaviourfromroadusers.TheSERapproachhasbeenpursuedtothelargestextentintheNetherlandsandtheUnitedKingdombutithasalsobeenofsomeinterestinNewZealand.In2004,theNationalRoadSafetyCommitteeandtheMinistryofTransportarticulatedanewNationalSpeedManagementInitiativewhichstated“Theemphasisisnotjustonspeedlimitenforcement,itincludesperceptualmeasuresthatinfluencethespeedthatadriverfeelsisappropriateforthesectionofroaduponwhichtheyaredriving–ineffectthe‘selfexplainingroad”’(NewZealandMinistryofTransport,2004).Incognitivepsychologicalterms,theSERapproachattemptstoimproveroadsafetyviatwocomplementaryavenues.Thefirstistoidentifyanduseroaddesignsthatafforddesirabledriverbehaviour.Perceptualpropertiessuchasroadmarkings,delineatedlanewidth,androadsideobjectscanfunctionasaffordancesthatserveasbuiltininstructionsandguidedriverbehaviour,eitherimplicitlyorexplicitly(Charlton,2007a;Elliottetal.,2003;Welleretal.,2008).Thisworkismoreorlessadirectdevelopmentofworkonperceptualcountermeasures,perceptualcuesintheroadingenvironmentthatimplyorsuggestaparticularspeedorlaneposition,eitherattentionallyorperceptually(Charlton,2004,2007b;Godleyetal.,1999).AsecondaspectoftheSERapproachistoestablishmentalschemataandscripts,memoryrepresentationsthatwillallowroaduserstoeasilycategorisethetypeofroadonwhichtheyare.1.2.LocalisedspeedmanagementThetraditionalapproachestoimprovingspeedmanagement,trafficcalmingandlocalareatrafficmanagement(LATM)havefocussedontreatingspecificproblemlocationsor“blackspots”inresponsetocrashoccurrencesorcomplaintsfromthepublic(Ewing,1999).Apotentialdi