ANALYSIS OF INJURY AND NON-INJURY CRASHES IN CALIF

PAPERNO:991438PREPRINTDuplicationofthispreprintforpublicationorsaleisstrictlyprohibitedwithoutpriorwrittenpermissionoftheTransportationResearchBoardANALYSISOFINJURYANDNON-INJURYCRASHESINCALIFORNIAWORKZONESAsadJ.KhattakDepartmentofCityandRegionalPlanning3140NewEastBuildingUniversityofNorthCarolinaChapelHill,NC27599Tel[phone],Fax[phone],[e-mail]~khattak/res951.htmAemalJ.KhattakDepartmentofCivilEngineeringNorthCarolinaStateUniversityRaleigh,NC27695Email:[e-mail]:[e-mail]15,1998TransportationResearchBoard78thAnnualMeetingJanuary10-14,1999Washington,D.C.Khattak,Khattak,&Council1ABSTRACTThereisconcernovertherisingworkzonecrashesandfatalitiesintheUnitedStates.Annually,thereareapproximately700-800fatalities,24,000injurycrashes,and52,000property-damage-onlycrashesinworkzones,costingseveralbillionsofdollarsindamages.Fromthemotorists'perspective,workzonesrepresenthazardousandhighriskdrivingconditions.Meanwhile,workzonesarelikelytoincreaseinnumber,duration,andlengthbecauseoffuturehighwayreconstructionneeds.Thisstudyexploresbothinjuryandnon-injurycrashratesonlimited-accessroadwaysinCaliforniabeforeandduringthetimethattheywereworkzones.The1992-1993HighwaySafetyInformationSystem(HSIS)crashandinventorydatamergedwithworkzonedurationandlengthdataareanalyzed.Thesampleconsistsof“before”and“during”dataon36freewayworkzones.Thecrashrateduringtheworkzoneperiodishigher(+21.5%)thanthebeforeworkzoneperiod.Inboththebeforeandduringworkzoneperiods,thenon-injurycrashratesarehigherthantheinjurycrashrates.Moreover,injuryandnon-injurycrashratesintheduringworkzoneperiodarehigher(+17.4%and+23.8%)thantherespectiveratesinthebeforeworkzoneperiod.Workzonesanalyzedinthisstudyincreasednon-injurycrashesrelativelymorethaninjurycrashes.NegativebinomialregressionmodelsofbeforeandduringworkzonesindicatethatcrashfrequenciesincreasewithincreaseinADT,duration,andlength.Theimportantfindingisthat,aftercontrollingforexposure,longerworkzonedurationsignificantlyincreasesbothinjuryandproperty-damage-onlycrashfrequencies.Theresearchfindingsstrengthenthepriorityofcurrentpolicy,research,andtechnologicalactivitiesconcerningshorteningofworkzoneduration.KEYWORDS:WorkZones,CrashRates,NegativeBinomialModel,CaliforniaKhattak,Khattak,&Council2INTRODUCTIONHighwayworkzonespresentanabnormalhighwayenvironmenttodrivers.Thepresenceofworkers,constructionmachinery,roadsideconstructionbarriers,andotherparaphernaliaassociatedwithworkzonescreateahighdegreeofconflictthatleadstohazardousconditions.AccordingtotheFatalAccidentReportingSystem(FARS),onaveragemorethan700fatalitiesoccurinworkzonesacrosstheUnitedStateseachyear.Figure1presentsworkzonefatalitiesintheUnitedStatesfrom1983to1996.Althoughtherecenttrendinfatalitiesisdecreasing,judgingfrompasttrendsitisdifficulttosaythatthiswillcontinue.Furthermore,thereareapproximately24,000injurycrashesand52,000PropertyDamageOnly(PDO)crashescostingbillionsofdollarsindamagesannually.Workzonesarelikelytoincreaseinnumber,duration,andlengthduetoemphasisonrepairandhighwayreconstruction—asignificantportionofallfederal-aidhighwayfundsarenowgearedtowardhighwayrehabilitation.Ingeneral,highwayagenciesuseseveralstrategiestominimizetheadverseeffectsofworkzones.Forexample,thedurationofworkzonesisanimportantpolicy-sensitivevariablethatisoftenusedtominimizeroaduserandworkzoneworkerexposure.Agenciesmayalsocontrolworkzonelengthtoreduceexposurebyundertakingtheworkinincrements.Anotherstrategyistodisseminateinformationabouttheexistenceoftheworkzonetothepublic.Thiscanreducetrafficonthesectionwhileitisaworkzone.Furthermore,onheavilytraveledhighways,workzoneactivitiesandclosuresareundertakenduringlowtrafficconditions.Ofthedifferentstrategiesavailable,thisstudyfocusesontheeffectsofworkzonelength,workzonedurationandtrafficoncrashfrequency.Anin-depthknowledgeofhowthesevariablesaffectcrashesinworkzonescanallowagenciestousethemmoreeffectivelyandperhaps,tradeoffoneagainsttheother.Theobjectivesofthisstudyareto:•Investigatecrashratesonlimited-accesshighwaysections“before”and“during”thetimethattheywereworkzones.•Empiricallyestimateandcomparetheeffectsofduration,length,andtrafficaswellastheirinteractiononinjuryandnon-injurycrashesinthebeforeandduringworkzoneperiods.Aliteraturereviewfollowsthisintroduction.Asectiondescribingtheresearchapproachfollowstheliteraturereview.Thenextsectionprovidessampledescriptionandcrashratecomparisonsbetweenthebeforeworkzoneandduringworkzoneperiods.Thenextsectiondescribesthemodelspecificationanddiscussesthenegativebinomialmodelingresults.Thelastsectionprovidestheconclusionsandimplicationsofthefindings.LITERATUREREVIEWTheliteratureprovidessignificantinformationondifferentaspectsofcrashesinworkzones.Withrespecttothesizeoftheproblem,Stammer(1988)reportedthattheannualfatalitiesinworkzonesacrosstheUSincreasedfrom