by MR Parker Jr · 1989 · Cited by 155 — If the observer was on the north approach and the southbound driver took evasive action to avoid a collision with the left–turning vehicle, the event would be
42 pages
263 KB – 42 Pages
PAGE – 1 ============
TrafficConflictTechniquesforSafetyandOperations–ObserversManualPublicationNo.FHWA-IP-88-027January1989U.S.DepartmentofTransportationFederalHighwayAdministrationResearch,Development,andTechnologyTurner-FairbankHighwayResearchCenter6300GeorgetownPikeMcLean,Virginia22101-2296
PAGE – 2 ============
Thisobserver™smanualprovidesbasicbackgroundinformationforpersonswhoareassignedtoobservetrafficconflictsinthefield.Themanualcon-tainsdefinitionsoftrafficconflictswhichtypicallyoccuratintersectionsaswellasstep-by-stepinstructionsforconductingthesurvey.Experiencedobserversandengineerswillfindthemanualtobeahandyreferencesourceandanaidintrainingnewpersonnel.Personswhohavenotpreviouslyconductedatrafficconflictsurveyshouldreadthismanualcare-fullyasafirststepinlearninghowtoaccuratelyobserveandrecordtrafficconflicts.Stanley™R.Byington,DirectorOfficeofImplementationNOTICEThisdocumentisdisseminatedunderthesponsorshipoftheDepartmentofTransportationintheinterestofinformationexchange.TheUnitedStatesGovernmentassumesnoliabilityforitscontentsorusethereof.Thecontentsofthisreportreflecttheviewsofthecontractorwhoisresponsibleforthefactsandtheaccuracyofthedatapresentedherein.ThecontentsdonotnecessarilyreflecttheofficialviewsorpolicyoftheDepartmentofTransportation.Thisreportdoesnotconstituteastandard,specification,orregulation.TheUnitedStatesGovernmentdoesnotendorseproductsormanufacturers.Tradeormanufacturers™namesappearhereinonlybecausetheyareconsideredessentialtotheobjectofthisdocument.
PAGE – 3 ============
TechnicalReporfDocumentationPage1.ReportNo.2,GovernmentAccessionNo.3.Recip,ent™sCa+alogNCI.FHMA-IP-88-0274.TitleandSfibt,tle5.ReportDafeTRAFFICCONFLICTTECHNIQUESFORIawv~989SAFETYANDOPERATIONS6,PerformingOrgon,za?ionCodeObserversManual8.‚Per{orm,ngOrganizationResortNo.7.Author(s)M.R.Parker,Jr.andflC.V.Zegeer9.PerformingOrgonizotionNameandAddress10.WorkUn,tNo.(TRAIS)MartinR.ParkerandAssociates,Inc.NCP3A9CO09338549LaurenwoodDrive11,ContractorGrantNo.Wayne,Michigan48184-1073DTFH61-86-C-0012313.TypeofReportandP,:riodCovered12.SponsoringAgencyNameandAddress,ManualOfficeofImplementation(HRT-20)October1986-June1988FederalHighwayAdministration6300GeorgetownPike,T-30414.SpoflsoriflgAgencyCodeMcLean,Virginia2210115.SupplementaryNotesFHWAContractManager:PeterJ.Hatzi(HRT-20)16.AbstractThismanualprovidesbasicbackgroundinformationandstep-byŒstepproceduresforconductingtrafficconflictsurveysatsignalizedandunsignalizedintersections.Themanualwaspreparedasatraininga~dandreferencesourceforpersonswhoareassignedtheresponsibilityofconductingtrafficconflictobservationsatintersections.Basedonpreviousresearchandexperiences,thesur~eytechniquesdescribedinthismanualprovideastandard,cost-effectivemethod[oraccuratelyobservingandrecordingtrafficconfllcts.Themanualcontainsdefinitionswithillustrationsandex.arnp~esofcon.flic~tyl)es,andinstructionsforconductingthefieldactlv~tles,lncludlngtimeschedules$forms,andotherdetails.Theresultsoftrafficconflictobservationsareusedtodiagnosesafetyandoperationalproblemsandtoevaluatetheeffectivenessoftreatments*Observertrainingtechniques,aswellasproceduresforanalyzingandinter–pretingtheresultsofconflictsurveys,arepresentedintheengineerIsguide(FHWA-Ip-88-026)e17.KeyWords18.DistributionStatementTrafficconflicts,Accidents?Norestrictions.ThisdocumentIntersections,Manualobservations,isavailablethroughtheNationalAccidentsurrogates,Train~ng~TechnicalI}~formationService,Evasivemaneuvers,PedestriansSpringfield,Virginia22fl161.19.SecurityClassif.(ofthisreport)Š~fi20.SecurityClassif.(ofthispage)UnclassifiedUnclassified1IIIFormDOTF1700.7(8-72)Reproductionofcompletedpageoutborized
PAGE – 4 ============
s(Cz22[Z~026!81L191%1@l$1ElIII016™~91™9‚z‚fiill1™IiIllIll1™1‚lfi!I11111!11111111111111Illlilllillll1111!11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111!111111111111!111Ill!lillllllll111/111111!1,1111Ill/111111111111‚1™/fl1™‚ill™‚1™/™1™‚l™l™l™I™ll™‚l™l™l™‚1™[™[™[lit1111III1/11/11[1Ill1[[Ill,11,,,,,,,,,,,,,,,,,,,,,,,,98&4321™1™1™‚1™/™1™1,fi*.Sv0u0
PAGE – 5 ============
TABLEOFCONTENTSSectionPage,-.CHAPTER1-INTRODUCTIONBackground..0..,.0..e.0e..TrafficConflictSur\/ey.e.<,.CHAPTER2-TRAFFICCONFLICTDEFINITIONS!,.GeneralDefinition..e..,,0OperationalDefinitions..OtherTypesofTrafficEvents.0CHAPTER3-RECOGNIZINGTRAFFICCONFLICTS.Exampless.UnusualIntersectionGeometries..,,CHAPTER4-STARTINGTHETRAFFICCONFLICTSURVEY..e4..oee~e.floflPreparingfortheSurvey<,0..ArrivingattheStudyLocation..CHAPTER5-CONDUCTINGTHESURVEY..0..e..!0..s..eTimeSchedulingoe..a..a.,,44..=.UsingtheCountBoard..s.TheConflictForm4..CollectingOtherData....0.CompletingtheSurveye..e..e.eaee..,,.REFERENCES..$..11444515151518202021242426283035353536iii
PAGE – 6 ============
123456789101112131415 16171819202122232425262728Atrafficconflictwithanoncomingleft-turnvehicle.Atrafficconflictwithacross-streetvehicle..Left-turn,same-directionconflict.s00.O..Right-turn,sameŒdirectionconflict..0e.e.e..Slow-vehicle,same-directionconflict.0Lane-changeconflictOOpposingleft-turnconflict8..0a.e..00.Right-turn,crossŒtrafficŒfromŒrightconflictLeft-turn,cross-traffic-from-rightconflict.Through,cross-traffic-from-rightconflictRight-turn,cross-trafficŒfromŒleftconflict..oo.o..oOLeft-turn,cross-traffic-from-leftconflict..Through,cross-traffic-from-leftconflict.Opposingright-turn-on-redconflict.m.oPedestrian,far-sideconflict,e..0..Pedestrian,nearŒsideconflict00..OO.OOSlow-vehicle,same-directionsecondaryconflict.Right-turn,crossŒtrafficŒfrom-rightsecondaryconflict..IntersectionlayoutfortheexampletrafficsituationsTypicalintersectiondiagramshowingobserverpositions..ConflictobserverinpickupparkedontheintersectionapproachConflictobserverinchair.0..Sitediagramshowingobservationlocationsandapproachvolume.TrafficTrafficExampleOn-siteTrafficconflictcojntboard.Oconflictrecordingform.0..0ofupdatinganinventoryofexistinghighwayfeatures..observationreport.volumecountrecordingform.0..Page33777789910111111121313141416222223262729313334LISTOFTABLESTablePage1Typicall-hourtimeschedule.0.Q..00..0..00..0m.25iv
PAGE – 8 ============
But,therearemanyproblemswithaccidentdata.Allaccidentsarenotreported.Duetomanpowerandbudgetlimitationsinrecentyears,thereisagrowingtrendnationwidebypoliceagenciesnottoreportpropertydamageonlyaccidents.Forexample,in1982inMaryland,reducedaccidentreportingresultedinalossof40percentofthetotalnumberofaccidentspreviouslyreported.[zlIncompleteaccidentdatamakestheidentificationofroadwayhazardslessaccurate.Sometimesdataerrorsandincompleteinformationarefoundinaccidentrecords.Also,accidentsarefairlyinfrequentandhappensporadically,soalongtimeisneededtocollectenoughaccidentdatatobeuseful.Forexample>thenumbersofaccidentsatoneintersectionfromyeartoyearare10,24,12,20,18,14,20,10,14.Ifonelookedatonlyoneortwoyears,onewouldnotknowwhatistypical.Isit10to14peryear,orisit14t020peryear?Thisisastatisticalproblemthatmanypeopledonotappre-ciate.Peopleoftenoverreacttoarashofaccidentsorasevereaccidentthatmaybejustanormalstatisticalfluctuation.Additionally,accidentrecordssometimesarenothelpfulinpinpointingspecifichazards.Forthesereasons,othertrafficindicatorsareuseful.TheTrafficConflictTechniqueisoneimportantwaytomeasuretheaccidentpotentialofhighwayintersectionswithouthavingtowaitforaccidentstohappen.Formanyyearstrafficengineershavemadeobservationsoftrafficoperationstoobtaincluesthatareusefulinidentifyingunsafeconditionsandoperationalproblems>buttheprocedureswerebasedonopinionandjudg-ment.In1967,tworesearcherswiththeGeneralMotorsResearchLaboratoriesdevelopedasetofformaldefinitionsandproceduresforobservingtrafficconflictsatintersections.[3JTheresearchersidentifiedtrafficconflictpatternsforover20correspondingaccidentpatternsatintersections.TheprocedurebecameknownastheTrafficConflictTechnique.Becauseeachtrafficconflictwasbasedonaparticularaccidenttype,thetechniquewasconsideredtobeameasureofaccidentpotential.Conflictsweredefinedastheoccurrenceofevasivevehicularactionsandwererecognizablebybrakingand/orweavingmaneuvers.Figures1and2showtwotrafficconflicts.Infigure1,thedriverinthepickupismakingaleftturnontothecrossstreetcausingthedriverofthethroughcartobraketoavoidcollision.Infigure2,thedriverinthepickuponthecrossstreetismakingarightturnontothemainstreetcausingthedriverofthecartoweavetothelefttoavoidacollision.Thesearejusttwoexamples,buttheyshowthattrafficconflictsaresituationswhereadriverbrakesorswervestoavoidacollision.In1979additionalextensivefieldtestingwasconductedtodevelopstandarddefinitionsandrefinethedatacollection~roceduretoensurethattrainedobserverscouldprovideaccurateresults.[41Thedefinitionsandprocedurespresentedinthismanualweretakenfromthatresearchstudy.Anothermajorstudy,completedin1985~providedproofthatsometrafficconflictsandaccidentsatintersectionswererelated.[51Infact,theresearchersfoundthattrafficconflictsaregoodsurrogatesforaccidents.Thismeansthatconflictdatamaybeusedasasubstituteforaccidentdata.2
PAGE – 10 ============
TrafficconflictsurveyAtrafficconflictstudyisusuallyconductedunderthedirectionofatrafficengineerwhodeterminesthatthestudyisneeded,schedulestheactivities,supervisesdatacollection?andperformsorsupervisestheanalysis.Theengineeralsointerpretsthefindingsandmakesdecisionsandrecommendationsconcerningintersectionimprovements.Fielddatacollectionisnormallythefunctionoftraffictechniciansand/orplanningpersonnel.Anengineer™sguideisavailablefortheengineerwhowillmakethedecisionsaboutwhereandwhentoconductaconflictstudy,andhowtoanalyzeandinterprettheresults.[1]Atrafficconflictsurveyusuallytakesfromseveralhourstoseveraldaysofcarefulmanualobservationoftrafficatanintersection.Specificproceduresareusedtoassureuniformdatacollectionsothatvalidcom-parisonsandjudgmentscanbemade.Asurveyrequiresoneormoreobserverswhofollowasetscheduleandperformanumberofseparatebutrelatedtasks.Thesetasksincluderecordingdimensionsandotherdetailsabouttheinter-sectionsuchasthetypeoftrafficcontroldevicesinplace.Theobserverisalsorequiredtomakejudgmentsaboutthetrafficflowproblemsandtheircauses~andmostimportantly,toobserveandrecordtrafficevents.Nosophisticatedequipmentisneededtomakeaconflictsurvey.InthepastsomeagencieshaveusedmotionpictureorvideoequipmenttorecordconflictdataYhowever,toimproveaccuracyandreducedatacollectioncosts,manualobservationsofconflictsinthefieldarerecommended.Chapter2ofthismanualprovidesdetaileddefinitionsofthetypesoftrafficconflictsthatareobservedandrecordedinaconflictsurvey.Inchapter3,examplesofseveraltrafficsituationsaregivenalongwithaninterpretationofhowtheseeventsshouldbehandledusingthetrafficconŒflictdefinitions.Chapter4describeshowtoprepareforatrafficconflictsurvey,includinginstructionsandsuggestionsforgettingstarted.Chapter5tellshowtoconductthesurvey,andincludestimeschedules$formstobecompleted,andotherdetails.Inthissectionthegeneralconceptofatrafficconflictisdiscussedfollowedbythedefinitionsofspecifictypesofconflictsforintersections.GeneralDefinitionAtrafficconflictisaneventinvolvingtwoormoreroadusers,inwhichtheactionofoneusercausestheotherusertomakeanevasivemaneuvertoavoidacollision.Generally,theroadusersaremotorists,butthedefinitionalsoincludespedestriansandcyclists.Theactionofthefirstuserincludesavarietyofmaneuverssuchasturningleftacrossthepathofathroughvehiclejustasthethroughvehicleisenteringtheintersectionarea;turningfromthecrossstreetintothepathofathroughvehicle;andslowingtoturnatthecrossstreetplacingafollowingvehicleindangerofarear-endcollision.The4
PAGE – 11 ============
generaldefinition,however,doesruleoutactionsthatnearlyalldriverstakeunderthesameconditionssuchasnormalstoppingforaSTOPsignorredtrafficsignal.Conflictsarevehicleinteractionswhichcanleadtoaccidents.ForIaconflicttooccur,theroadusersmustbeonacollisioncourse;i.e.,theusersmustbeattemptingtooccupythesamespaceatthesametime.Th~aprimaryrequirementofatrafficconflictisthattheactionofthefirstuserplacestheotheruseronacollisionpathunlessevasiveactionistakenbytheotherusertoavoidtheaccident.Sometimestheotheruseriseitherunawareofthecollisionpotentialorhaspoorjudgmentinestimatingtiresintervalsandclearancesanddoesnotmakeanevasivemaneuver.Collisionsandnearmisssituationsthatoccurwithoutevasivemaneuvers,orwhenthsevasiveactionisinadequateorinappropriateforconditions,arealsorecordedasconflictsunderthegeneraldefinition.Anintersectiontrafficconflictisdescribedasaneventinvolvingthefollowingstages.Stage1.Thefirstvehiclemakesamaneuver;e.g.,pullingoutfromthecrossstreet.Stage2.Asecondvehicleisplacedindangerofacollision.Stage3.Thedriverofthesecondvehiclereactsbybrakingorswerving.Stage4.Thesecondvehiclethencontinuestoproceedthroughtheintersectionarea.Thelaststageisnecessarytoconvincetheobserverthattheseco~ldvehiclewasactuallyrespondingtotheman~:~verofthefirstvehicleandnot,forexamplejtoatrafficcontroldeviceornearbydrivewayormedianopening.Theevasivemaneuvertakenbythesecondvehicleisevidencedbyobviousbrakingorswerving.BrakingisusuallyobservedasbrakeŒlightindications,however,somevehiclesaredrivenwithinoperativebrakelights.Anoticeabledivingofthevehicleorsquealingoftiresintheabsenceofbrakelightsisacceptableevidenceofanevasivemaneuver.OperationalDefinitionsWithinthisgeneralframework,abasicsetofconflictdefinitionsweredevelopedforintersections,correspondingtothedifferenttypesofmaneuversandrelatedaccidentpatterns.Similartothsmannerinwhichaccidentsaregroupedbytypeofcollision,trafficconflictsarecategorizedbytypec]fmaneuver.Theprimarytypesofintersectionconflictsare:eSamedirection.eOpposingleftturn.eCrosstraffic.eRight-turnŒon-red.aPedestrian.eSecondary.
263 KB – 42 Pages