JaeyoungLee,Ph.D.,MohamedAbdel-Aty,Ph.D.,andLingWang,Ph.D. 8/20/2016

UtilizingMicroSimulationtoEvaluatetheSafetyandEfficiencyoftheExpresswaySystem

Overview

Thisprojectanalyzedthesafetyofthreeexpresswaysbasedonaveragedailytraffic,averagehourlytraffic,andmicroscopictrafficdataatfive-minuteintervals.Themodelingresultsshowedthatweavingsegmentshadexperiencedmorecrashesthanothersegmenttypes.

Thecrashmechanismsofweavingsegmentswereexploredusingreal-timecrashanalysis.Then,activetrafficmanagement(ATM)strategies,

rampmetering(RM)andvariablespeedlimit(VSL),wereidentifiedtobepotentialcountermeasurestoimprovethesafetyofweavingsegments.Subsequently,awell-calibratedandvalidatedmicroscopicsimulationnetworkwasbuiltforacongestedweavingsegment.ThesimulationresultsverifiedthatATMcansignificantlyimprovethetrafficsafetyofthestudiedweavingsegments.

Figure1.Averagecrashrateforthreestudiedexpressways

(crashesperhourspersegment)

Figure2.StudysubjectofVISSIMsimulation

JaeyoungLee,Ph.D.,MohamedAbdel-Aty,Ph.D.,andLingWang,Ph.D.

StudyTasks

1) IdentifyingthemostdangerousexpresswaysegmenttypebasedonsafetyanalysesusingADT,AHT,andmicroscopictrafficdata;2) Exploringthecrashmechanismofthemostdangerousexpresswaysegmenttypeusingthereal-timesafetyanalysis;3) Buildingawell-calibratedandvalidatedVISSIMnetworkforanexpresswaysegmentthathashighcrashpotential;and4) TestingtheimpactofATMonthesafetyoftheexpresswaysegmentidentifiedbyTask3.ConclusionsandRecommendations

1) InADT-based,AHT-based,andmicroscopic-traffic-basedsafetystudies,allresultsillustratedthattheexistenceofaweavingsegmentcouldincreasecrashpotential;2) Themicroscopictraffic(five-minuteintervals)dataisthemostsuitabletrafficdataifATMisusedtoimprovethesafetyofasegmentinrealtime;3) Themaincrashcontributingfactorsforweavingsegmentsarespeeddifferencebetweenthebeginningandendofweavingsegmentsandweavinginfluencelength.Bothfactorshavepositiveimpactoncrashrisk;4) Throughmicroscopicsimulation,ATMstrategiesimprovedthesafetyofacongestedweavingsegmentbyreducingcrashoddsratiobecausetheyreducedthespeeddifferenceorweavinginfluencelengthorboth;5) TheproposednewRM,whichtookbothtrafficoperationandsafetyintoconsideration,wasbetterthantraditionalRMbecauseitprovidedsafertraffic;and6) Theintegratedstrategy(RM-VSL)producedlowerconflictnumbersthanRMalonewhenon-rampqueuelengthwascontrolled.

“Oncecrashmechanismshavebeenidentifiedusingreal-timesafetyanalyses,microscopicsimulationcanbeusedtotestandverifytheimpactofactivetrafficmanagementonthesafetyofexpresswaysegments.”

Figure3.Weavingsegmentmicrosimulationnetwork