nchrp 03-115 - uninterrupted flow - wp 4 - freeway method integration - 20140415

CopyNo._____

NCHRPProject03115ProductionofaMajorUpdatetothe

HighwayCapacityManual2010

UninterruptedFlowWorkingPaper#4FreewayMethodologyIntegrationPlan

Preparedby:

BastianSchroeder,NaguiRouphail,BehzadAghdashi,andAliHajbabaieITREatN.C.StateUniversity

Preparedfor:NationalCooperativeHighwayResearchProgram

TransportationResearchBoardNationalResearchCouncil

TransportationResearchBoard

NASNRCLIMITEDUSEDOCUMENT

Thisreport,notreleasedforpublication,isfurnishedonlyfortomembersof,orparticipantsintheworkof,theNational

CooperativeHighwayResearchProgram.Itistoberegardedasfullyprivileged,anddisseminationoftheinformationincludedhereinmustbeapprovedbytheNCHRP.

April2014

Kittelson&Associates,Inc.

ITREatNorthCarolinaStateUniversityMcTransCenterUniversityofFlorida

Dr.RogerRoessStrongConceptsWriteRhetoric

NCHRP03115:ProductionofaMajorUpdatetotheHighwayCapacityManual2010UninterruptedFlowWorkingPaper#4:FreewayMethodologyIntegrationPlan TableofContents

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TableofContents

TableofContents.......................................................................................................................................ii1. Introduction...................................................................................................................................................12. ReviewofExistingMethodologies.......................................................................................................13. MethodologyFramework.........................................................................................................................24. ProposedMethodologyFlowCharts....................................................................................................35. PartA:CoreFreewayFacilityAnalysisComputationalSteps...............................................66. PartB:ComprehensiveReliabilityAnalysisComputationalSteps......................................97. PartC:ReliabilityStrategyAssessment(ATDMEffect)ComputationalSteps...........11

AppendixExistingMethodologyFlowCharts............................................................................13

NCHRP03115:ProductionofaMajorUpdatetotheHighwayCapacityManual2010UninterruptedFlowWorkingPaper#3:FreewayMethodologyIntegrationPlanTableofContents

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1. INTRODUCTIONThisworkingpaperdescribesaproposedintegratedmethodologyforfreewayfacilityevaluationintheHCM2010MajorUpdatetobepreparedundertheauspicesofNCHRP03115.Aspartofthatproject,thecorefreewayfacilitiesmethodology(HCM2010Chapter10)isenhancedthroughthreeprincipalresearchactivities:

1. FreewayFacilitywithManagedLanesAnalysis(NCHRP396),2. FreewayFacilityReliabilityAnalysis(SHRP2L08),and3. FreewayFacilitywithActiveTrafficandDemandManagement(ATDM,FHWA).

Inadditiontothesethreecoreenhancements,additionalresearchonworkzoneeffects,truckimpacts,andothersenhancementsneedtobeintegratedinthecoremethodology.Thefocusofthispaperisonthemethodologyitself,andnotthespecificorganizationofthematerialwithintheHCM2010MajorUpdate.Aseparatedworkingpaperwilldescribeproposedoutlinesandoptionsforthefreewayfacilitieschapter(s).

2. REVIEWOFEXISTINGMETHODOLOGIESTheteamcarefullyreviewedtheexistingmethodologiesofthevarioussourcesmentionedabove,whicharealsoprovidedintheappendixofthisworkingpaper.Severalobservationsaremade:

ThemanagedlanemethodologydevelopedunderNCHRP396assumesintegrationwithinthecurrentChapter10freewayfacilitiesmethodology;

ThereliabilityandATDMmethodologiesaredesignedtobuildupontheexistingHCM2010Chapter10,andtreatthecurrentmethodasthecomputationalcore;

BothreliabilityandATDMmethodsrelyontheconceptofscenariogenerationtoconsiderimpactofweather,incidents,demandvariability,etc.onthefacility.Thetwomethodsdifferintheirapproachtoscenariogeneration,andaconsistentapproachishighlydesirabletoachieveintegrationinHCM2010MajorUpdate;

TheATDMmethodcouldbeconsideredasbuildinguponthereliabilitymethodology,wheretheATDMbeforeanalysisisconceptuallysimilartothewholeyearanalysisperformedinthereliabilityprojectalbeitwithsomedifferencesinscenariogenerationasdiscussedinthepreviousbullet;

Allexistingmethodologiescouldbeconsideredhighlevel,whereimportantindividualstepsthatcouldhelpuserunderstandingareleftout;

Allmethodologiesrelyontheuseofcomputationalengines(variousformsofFREEVAL),butinthemethodologyitisunclear,whichstepsareperformedmanuallybytheuser,andwhichareautomatedintheengine;

Noneofthemethodologiesincludedesignatedstepsoncalibrationandvalidation,whichhavebeenidentifiedbytheprojectpanel,AHB40,andtheusercommunityasbeinghighlydesirable;


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Thecoremethodologyforthefreewayfacilitymethodologylackssufficientdetailforausertounderstandwhatstepsshouldbeconductedpriortoapplyingthecomputationalengine,andhowtogathervaliddata.MoredetailisdesiredtomeetthepractitionerfocusdesiredforHCM2010MajorUpdate;and

Workzonescantaketheformoflongtermandshorttermworkzones,wherelongtermworkzones(durationofmanymonths,orevenyears)areoftentreatedasentirelyseparatebaseanalysisfiles.Shorttermworkzonesbehavesimilartoincidents(capacityandspeedadjustments),butwiththedifferencethattheyareoftenscheduled.However,someworkzonesaremorerandom,suchaspavementrepairandmaintenancework,whichhappensonanasneededbasiswithoutsignificantadvancescheduling.Thepresenceofworkzoneactivityduringthepeakstudyperioddependsonthetypeoffacility,withmanyagencieslimitingconstructionactivitiestooffpeakperiodsonurbanfreewaysservingcriticalmobilityneeds.

3. METHODOLOGYFRAMEWORKFromtheobservationsabove,theteamproposesaframeworkthatdividestheintegratedfreewayfacilitiesmethodologyintothreedistinctparts:

PartA:CoreFreewayFacilityAnalysis(SingleStudyPeriod)ThisisamodificationoftheexistingHCM2010methodology,withintegratedmanagedlaneanalysisstepsfromNCHRP396,andwithcriticalenhancementstoaiduserunderstanding.Thenumberofstepshasbeenexpandedtoclearlydesignateeachstepinthemethodology,withafocusonassistingpractitionersapplythemethodologycorrectly.Themethodfurtherhasbeenaugmentedwithcalibrationandvalidationsteps,andmoreclearlydistinguishesstepsrequiredtobeperformedmanuallybytheusers,vs.thosetypicallyautomatedinacomputationalengineorsoftware.

PartB:ComprehensiveReliabilityAnalysis(WholeYearAnalysis)ThissecondpartintegratesthereliabilitymethodologyandscenariogenerationprocessfromSHRP2L08.ItbuildsuponthecoremethodologyfromPartA,andprovidesdetailedstepsforconductingareliabilityanalysis.ThecomputationalstepshavebeenexpandedfromtheSHRP2L08methodtointegratescenariogenerationwithintheoverallmethod,aswellasprovidingclearguidancetotheuseroneachstep.SimilartopartA,themethodincludesacalibration/validationstep,andclearlydistinguishesmanualfromautomatedsteps.

PartC:ReliabilityStrategyAssessment(ATDMEffectAnalysis)ThisthirdpartbuildsuponthecompletedreliabilityanalysiswithanassessmentofATDMstrategies.ThepartCmethodologyisconsistentwiththemethodologydevelopedforFHWAonATDMevaluation,withthekeydifferencethatthebeforeATDManalysisissynonymouswithPartBabove.Further,themethodologyhasbeenexpandedtoincludeacalibration/validationstep,todistinguishmanualfromautomatedsteps,andtoprovideconsistencyinterminologywithotherparts.


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ItisassumedthatPartAwouldconstitutethecoremethodology,whilepartsBandCrepresentadaptationsandextensionsofthemethodologyforreliabilityandATDMassessment,respectively.ThemethodfurtherassumesthatlongtermworkzonesaretreatedasastandaloneevaluationforpartsA,B,andC,astheirdurationoftenspansmanymonthsorevenyears(i.e.mostorallofthereliabilityreportingperiod).Assuch,onlyshorttermworkzonesshouldbeincludedinthereliabilityscenariogenerationprocess,usinguserdefinedinputsforfrequency,location,severity,andprobability.Inthescenariogenerationsteps,theseshorttermworkzoneswillthenbeconsideredasasubcategoryofincidents.

4. PROPOSEDMETHODOLOGYFLOWCHARTSTheproposedmethodologyflowchartsforthethreepartsareshownonthenextfewpages,followedbyadiscussionofcomputationalstepsforeachpart.


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Legend*StepautomaticallyexecutedbyComputationalEngine(doubleborder)+StepappliestoManagedLaneAnalysisOnly

LQ=LengthofQueue

LQ=LengthofQueue

ACoreFreewayFacilityAnalysis(SingleStudyPeriod)

StepA1:DefineStudyScopeSpatialExtent, TemporalExtent,Extensions

StepA2:Divide FacilityintoValidationSectionsandSegments

StepA3:GatherInputDataDemand,GeometryDetails, HeavyVehicles,etc.

StepA4:BalanceDemands

StepA5:CodeBaseandManagedLaneFacilityFREEVALComputationalEngine

StepA7:ComputeSegmentCapacities*HCM2010 segmentmethodologies

StepA8:CalibratewithAdjustmentFactorsForinitialrun,CAF=SAF=DAF=1.0forentirefacility

StepA9:MLCrossWeaveAdjustment+(AppliestoManagedLaneAnalysisOnly)

StepA10:ComputeDemandtoCapacityRatios(vd/c)*

vd/c


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Legend*StepautomaticallyexecutedbyEngine(doubleborder)+StepappliestoManagedLaneAnalysisOnly

BComprehensiveReliabilityAnalysis(WholeYearAnalysis)

StepB2:GatherReliabilityInputsDemand,weather,incidents,etc.

CalibratedBaseFilefromSingleScenario Anysis(StepA17)

StepB5:CombineDemand PatternsforSimilarDaysofWeekorMonthsofYears

StepB6:DefineDemandVariabilityperDayandMonthandAssigntoScenarios

StepB7:DefineWeatherProbabilitiesandImpactsandAssigntoScenarios

StepB8:DefineIncidentProbabilitiesandImpactsandAssigntoScenarios

StepB9:DefineShortTermWorkZoneandSpecialEventProbabilitiesandAdjustments

StepB10:GenerateFullScenarioListandScenarioProbabilities*

StepB11:PerformAnalysisforeachScenario*

StepB12:ComputeReliabilityPerformanceMeasures*

StepB13:ValidateAgainstFieldDataorExpertJudgment

Accept.Match?

StepB14:EstimateLOSandReportPerformanceMeasures*

Yes

No

OPTIONAL: Continue toATDMAnalysisStepC1

StepB1:DefineReliabilityReportingPeriod(RRP)andExcludeDays

StepB3:Define orRefineGlobalInputsUserdefinedglobalcalibrationparameters

StepB4:DefineorRedefineNumberofScenariosforReliabilityAnalysis

Figure2:ProposedMethodologyforPartBComprehensiveReliabilityAnalysis(WholeYear

Analysis)


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Legend*StepautomaticallyexecutedbyEngine(doubleborder)+StepappliestoManagedLaneAnalysisOnly

CReliabilityStrategyAssessment(ATDMEffectAnalysis)

StepC1:LimitScenarioList (OptionaltoStreamlineApplicationofATDMStrategies)

StepC2:SelectPoolofATDMStrategies

CalibratedReliabilityAnysis(StepB14)

StepC3:DesignATDMStrategyforFacility

StepC4: ConvertATDMInfotoOperationalInputs

StepC5:ProcessATDMScenarios*

StepC6:Compute PerformanceMeasures*

StepC8:Validate ResultsAgainstFieldDataorExpertJudgment

Accept.Match?

Yes

No

StepC9:EstimateLOSandReportPerformanceMeasures*

StepC7:ProcessBefore&AfterComparison*

Figure3:ProposedMethodologyforPartCReliabilityStrategyAssessment(ATDMEffectAnalysis)

5. PARTA:CoreFreewayFacilityAnalysisComputationalSteps

Thefirstpartofthefreewayfacilitiesanalysisconsistsofseventeencomputationalstepsasdiscussedbelow:

StepA1:DefineStudyScopeInthisstepinitialstep,theanalystdefinesthespatialextentofthefacility(startandendpoints,totallength)andthetemporalextentoftheanalysis(numberof15minutetimeperiods).Theanalystshouldfurtherdecidewhichstudyextensions(ifany)applytotheanalysis(managedlanes,reliability,ATDM)

StepA2:DivideFacilityintoValidationSectionsandSegmentsInthisstep,theanalystfirstdefinesthenumberofvalidationsectionsfromgorepointtogorepointalongtheselectedfacility.WhiletheHCManalysisdoesnotdirectlyusetheconcept


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ofvalidationsections,theyarebelievedtobemoreintuitiveandunderstandablebyusers,andfurthermatchmostfreewaydatabases(e.g.INRIX,PEMS,etc.),whichallprovideperformancemeasuresfromgoretogore.Thisconsistencyisconsideredcriticalforcalibrationandvalidationofthefreewayfacility.TheanalystthenfurtherdividesvalidationsectionsintoHCMsegments(basic,merge,diverge,weave,overlappingramp,ormanagedlanesegment).ExpertjudgmentmaybeneededforsegmentsthatdonotcleanlyfittheHCMdefinitions.Thefirstandlastsegmentmustalwaysbeabasicsegment,andthesemaybeconsideredashalfvalidationsections,asonlyonegorepointisincludedineach.Forfacilitieswithmanagedlanes,thisstepincludesthedefinitionofparallellanegroupsformanagedlanesandgeneralpurposelanes.

StepA3:GatherInputDataThisstepgathersdetailedinputdataincludingvehicledemands,geometricdetails(numberoflanes,segmentlengths,lengthsofaccelerationanddecelerationlanes),heavyandrecreationalvehiclepercentages,freeflowspeeds,andweavingsegmentdetails.Dataareneededin15minuteintervals,andtheuserneedstocarefullydistinguishbetweendemandandvolumeserved,wherethelattermaybemeteredrelativetothetruedemandduetocongestion.

StepA4:BalanceDemandsForforecasteddata(fromatrafficmodel)thisstepbalancesflowsthroughoutthefacility.Forfielddata,thisstepbalancesthesumsofinputsandoutputs.Ifnecessary,offrampdemandsdownstreamofcongestionmayneedtobeadjustedtoachievedemandbalance.

StepA5:CodeBaseFacilityThisisthefirststeprequiringtheuseofacomputationalengineorsoftware.ThestepreferencestheFREEVALuserguidefordetailedguidanceforcodingthebasefacility.

StepA6:SetGlobalParametersThisstepdefinesglobalparametersthatareneededforcomputationandcalibration.Thecalibration/validationloopreturnstothissteptoadjustglobalparameters,includingjamdensity,queuedischargecapacitydrop,terraintype,etc.

StepA7:ComputeSegmentCapacitiesThisstepcomputessegmentcapacitiesbasedontherespectiveHCMchaptersforbasic,mergeanddiverge,andweavingsegments.Nocapacityadjustmentsareperformedinthisstep.

StepA8:CalibratewithAdjustmentFactorsThisstepallowstheusertoadjustdemands,capacities,andfreeflowspeedsforthepurposeofcalibration.Thedemandadjustmentfactors(DAF),capacityadjustmentfactors(CAF),andspeedadjustmentfactors(SAF)canbemodifiedforeachsegmentandeachtimeperiod.Itisrecommendedthatthebaserundoesnotincludedanyadjustments,butthatDAF,CAF,andSAFareusedascalibrationtoolsinoneormoreiterationtomatchfielddata.

StepA9:MLCrossWeaveAdjustmentThisstepisonlyrequiredforfacilitieswithmanagedlanes,andimplementsafrictionfactorfortrafficfromageneralpurpose(GP)laneonrampweavingacrossGPmainlinelanestogettoamanagedlane


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accesspoint(orviceversa).ThecrossweaveadjustmentfactorisconceptuallysimilartoacapacityadjustmentfactorasusedinstepA8.

StepA10:ComputeDemandtoCapacityRatiosThisstepestimatesthedemandtocapacityratioforeachsegmentineachtimeperiod.Thisstepisthefirstpointwherethemethodcanjumpintotheoversaturatedcomputationalmodules,asopposedtousingtheHCMsegmentchaptersforperformanceestimation.Theoversaturatedmodule(stepA13)isinvokedassoonasanyonesegmenthasademandtocapacityratiogreaterthan1.0.Thecomputationsremainintheoversaturatedmoduleaslongasdemandexceedscapacityonanysegments,andaslongasthereareanyresidualqueuesonanysegment(queuedissipationafterdemandhasdropped).Assuch,themethodologychecksforresidualqueuesonthefacility,anddecideswhethertostayintheoversaturatedmodule,orwhethertoreturntoundersaturatedcomputations.

StepA11:ComputeUndersaturatedPerformanceMeasuresThisstepcomputestheperformanceofeachsegmentwithdemandtocapacityratiolessthan1.0andwithoutanyqueuingatanytimeduringthe15minuteanalysisperiod.

StepA12:ComputeOversaturatedPerformanceMeasuresThisstepisinvokedifanysegmenthasademandtocapacityratiogreaterthan1.0,andpersistsaslongasanysegmenthasaqueuelengthgreaterthanzero.StepA12representsanumberofsubstepsintheoversaturatedprocedure,whicharedescribedindetailinChapter25.

StepA13:ApplyMLAdjacentFrictionFactorThisstepadjuststheperformanceof(undersaturated)managedlanesforadjacentgeneralpurposelaneswithadensitygreaterthan35passengercarspermileperlane(pcpmpln),dependingontheseparationtypebetweenthetwolanegroups(paint,buffer,barrier).Thissteponlyappliestofacilitieswithmanagedlanes.

StepA14:ComputeLaneGroupPerformanceThisstepcomputestheperformancemeasureforthelengthofthefacilityforeachlanegroupseparately.Thissteponlyappliestofacilitieswithmanagedlanes.

StepA15:ComputeFacilityPerformanceMeasuresThisstepcomputesoverallfacilityperformancemeasuresforeachtimeperiodbyaggregatingtheindividualsegmentperformance.Followingthisstep,themaximumqueuelengthiscomparedtothefacilitylength,andtheanalystisencouragedtoexpandthelengthofthefacilityifthebasemaximumqueuelength(reoccurringcongestion)exceedsthefacilitylength.ForthereliabilityevaluationinpartB,thequeueisexpectedtoextendbeyondthefacilitylengthmorefrequently,duetoimpactsofweatherandincidents.

StepA16:ValidateAgainstFieldDataorExpertJudgmentInthisstep,themethodologyresultsarecomparedtofielddata,resultsfromanothermodel,orexpertjudgment.Additionaldetailsoncriteriaforcalibrationandvalidationofthefacilitywillbeprovidedinaseparateworkingpaper.Ifanacceptablematchisnotobtained,theanalysisreturnstostepA6andfollowingstepsforcalibrationadjustments.


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StepA17:EstimateLOSandReportPerformanceMeasuresforLaneGroupsandFacilityThisfinalstepofthecoremethodologyestimatestheLOSforeachsegment,lanegroup,andtheoverallfacilityforeachtimeperiod.

StepA17concludesthecorefreewayfacilitymethodologyforasinglestudyperiodanalysis.Atthistime,theanalystmaychoosetocontinuetoperformareliabilityanalysis.ItisnotedthattheAHB40committeemaydecidetoselectareliabilityperformancemeasureastheservicemeasureforfreewayfacilitiesandtodefineLOS(atleastforurbanfreeways).Inthiscase,thecontinuationtoPartBisnolongeroptional.

6. PARTB:ComprehensiveReliabilityAnalysisCOMPUTATIONALSTEPSThesecondpartofthefreewayfacilitiesanalysisconsistsoffourteencomputationalstepsasdiscussedbelow:

StepB1:DefineReliabilityReportingPeriod(RRP)andExcludeDaysInthissteptheanalystdefinesthelengthoftheRRP,whichistypicallyonecalendaryear,anddecidesonanydaystoexcludefromtheanalysis(e.g.holidays).Theanalystalsoneedstodefinethecalendardatefortheseedfile,whichisusedasabasisforanydemandadjustmentsinthereliabilityanalysis.

StepB2:GatherReliabilityInputsThisstepcollectsadditionalinputsneededforconductingareliabilityanalysis,includingdemandvariability(bydayofweekandmonthofyear),weatherdata,incidentrecords,workzoneinputs,andotherspecialevents.Somedefaultsandquickestimationmethodsareprovidedtoaidtheuser,whichwillbedescribedinmoredetailinthechapter.

StepB3:DefineorRefineGlobalInputsInthissteptheanalysthasachancetoreviseglobalinputsfortheanalysis,includingjamdensityandthequeuedischargecapacitydrop.Thisstepshouldideallynotbenecessary,astheseshouldhavebeendefinedandcalibratedinthecoreanalysisinPartA.Whiletheseparametersprovideadditionalcalibrationtoolsinthereliabilityanalysis,awellcalibratedbasefileishighlyrecommended,andadditionalchangesduringthereliabilityassessmentdiscouraged.Ingeneral,thereliabilityoutputisbettercalibratedbychangingotheradjustmentfactors,aswellastheunderlyingscenarioprobabilities.Theprimaryadjustmentfactorsforscenarioaredemandadjustmentfactor(DAF),capacityadjustmentfactor(CAF),andspeedadjustmentfactor(SAF).

StepB4:DefineorRedefineNumberofScenariosforReliabilityAnalysisThisstepisanewstepforthehybridscenariogenerationapproachthatwillbeproposedfortheHCM2010MajorUpdateinaseparateworkingpaper.Thegoalofthehybridapproachistoreducethenumberofscenariosfromseveralthousandtolessthanonehundredscenarios,whilestillcapturingeffectsofallsourcesofnonrecurringcongestion.Formostreliabilityapplications,alistof100scenariosisoftensufficienttocapturetheoneyearvariabilityinperformance.However,theanalystmaychoosetoincludemorerarescenarios(e.g.a5yearor10yearstorm),toevaluate


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impactsofveryrareevents.ForATDMevaluation,asmallernumberofscenariosisrecommendedtoallowforscenariospecificselectionofATDMstrategies.

StepB5:CombineDemandPatternsforSimilarDaysofWeekorMonthsofYearThisstepcombinesdaysoftheweekandmonthsoftheyearwithsimilardemandsintothesamecategorytostreamlinethescenariogenerationapproach.Atthisstage,theanalystfurtherdecideswhetherornottoincludeweekendsinthereliabilityanalysis.

StepB6:DefineDemandVariabilityperDayandMonthandAssigntoScenariosThisstepdefinesdemandadjustmentfactors(DAF)bydayoftheweekandbymonthoftheyearbasedonfacilityspecificdata.TheDAFisexpressedrelativetotheseedfiledatefromPartA.Defaultsforurbanandruraldemandpatternsareprovided,althoughfacilityspecificdataarepreferred.

StepB7:DefineWeatherProbabilitiesandImpactsandAssigntoScenariosThisstepdefinesweatherprobabilitiesforeachoftheHCMweathercategories,alongwithCAF,SAF,andDAFadjustmentfactors.Weatherprobabilitydefaultsareprovidedforthe101largestUSmetropolitanareas.CAFandSAFdefaultsareprovided,whileDAFhavetobeuserdefined.

StepB8:DefineIncidentProbabilitiesandImpactsandAssigntoScenariosThisstepdefinesincidentprobabilitiesforeachoftheHCMincidentcategories,alongwithCAF,SAF,andDAFadjustmentfactors,aswellasthenumberoflaneslostduetotheincident.CAFandSAFdefaultsareprovided,whileDAFhavetobeuserdefined.Twoquickestimationmethodsforestimatingincidentprobabilitiesareprovided,orfacilityspecificdatacanbeused.

StepB9:DefineShortTermWorkZoneandSpecialEventProbabilitiesandAdjustmentsThisstepdefinesprobabilitiesforanyshorttermworkzoneorspecialevent,alongwithCAF,SAF,andDAFadjustmentfactors,aswellasthenumberoflaneslostduetotheworkzone.Longtermworkzonesshouldbeevaluatedasastandalonereliabilityanalysis.ProbabilitiesandDAFsforshorttermworkzonesorspecialeventsneedtobeuserdefined;CAFandSAFdefaultsforworkzonesareprovided.Inthescenariogenerationstep,theseprobabilitieswillbetreatedasasubsetofincidentscenarios.

StepB10:GenerateFullScenarioListandScenarioProbabilitiesThisstepgeneratesthelistingofscenariosforreliabilityanalysisbasedonuserinputsonprevioussteps

StepB11:PerformAnalysisforeachScenarioThisstepautomaticallyprocesseseachscenariointheFREEVALcomputationalengine.

StepB12:ComputeReliabilityPerformanceMeasuresThisstepcomputesreliabilityperformancemeasuresfromtheresultsofallscenarios.Performance


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measuresincludethetraveltimedistribution,aswellasreliabilitymeasureslikedifferentpercentilesofTTI,bufferindex,andthereliabilityrating.

StepB13:ValidateAgainstFieldDataorExpertJudgmentInthisstep,thereliabilityresultsarecomparedtofielddata,resultsfromanothermodel,orexpertjudgment.Additionaldetailsoncriteriaforcalibrationandvalidationofthefacilitywillbeprovidedinaseparateworkingpaper.Ifanacceptablematchisnotobtained,theanalysisreturnstostepB3andfollowingstepsforcalibrationadjustments.

StepB14:EstimateLOSandReportPerformanceMeasuresThisfinalstepofthereliabilityassessmentmethodologyestimatesthereliabilityLOSforthefacility.

StepB14concludesthecomprehensivereliabilityanalysismethodology.Atthistime,theanalystmaychoosetocontinuetoperformanATDMevaluation.

7. PARTC:RELIABILITYSTRATEGYASSESSMENT(ATDMEFFECT)COMPUTATIONALSTEPS

Thethirdpartofthefreewayfacilitiesanalysisconsistsofninecomputationalstepsasdiscussedbelow:

StepC1:LimitScenarioListInthisstep,theanalystmayelecttoreducethenumberofscenariosfromPartBtoamoremanageablesizeforthepurposeofassessingATDMstrategies.Sincetheapplicationofstrategieshastobeperformedmanuallyatthispoint,alistof30scenariosmaybemorereasonablethan100.Themethodologywillautomaticallyadjusttheprobabilitiesofeachscenariotomatchtheprobabilitydistributionofthepopulationofscenarios.TheusermayselectasubsetofscenariostoreflectacertainconditionthatistargetedbytheATDMstrategyinquestion(e.g.snowremovalforinclementweatherdays),butshouldalwaysincludeother(nonweather)scenarios,astonotoverestimatetheeffectofthestrategyontheentirereliabilityreportingperiod.Statisticaltestsofhowwellthereducedscenariolistreflectstheoverallpopulationwillbeincludedinthecalibrationstep.

StepC2:SelectPoolofATDMStrategiesThisstepallowstheanalysttoselectwhichATDMstrategytoincludeintheevaluation.VariousstrategiesandtheireffectivenessaredescribedinHCM2010Chapter35.

StepC3:DesignATDMStrategyforFacilityFromthepoolofstrategies,theanalystmanuallyselectswhichstrategytoapplytowhichscenario.Theanalystmayselecttoapplyastrategyuniformlyacrossallscenarios,butmorecommonlywouldmatchaspecificstrategywithagivenscenario(e.g.weathermanagementforsnowevents,freewayservicepatrolsforincidents,etc.).

StepC4:ConvertATDMInfotoOperationalInputsThisstepconvertstheATDMstrategyintooperationalinputsincludingdemandadjustmentfactor(DAF),


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capacityadjustmentfactor(CAF),speedadjustmentfactor(SAF),andnumberoflanes.

StepC5:ProcessATDMScenariosThisstepevaluateseachscenariobasedonthegiveninputs.

StepC6:ComputePerformanceMeasuresThisstepcalculatesperformancemeasuresforthefacilitywiththeATDMstrategiesapplied.Resultsareprovidedforeachscenario,aswellasintheformoftheoveralltraveltimedistribution.

StepC7:ProcessBefore&AfterComparisonThisstepconductsabeforeandaftercomparisonofATDMstrategyeffectiveness,bycomparingtheresultsfromPartBwiththeresultsoftheATDManalysisofPartC.

StepC8:ValidateResultsAgainstFieldDataorExpertJudgmentInthisstep,theATDMresultsarecomparedtofielddata,resultsfromanothermodel,orexpertjudgment.Additionaldetailsoncriteriaforcalibrationandvalidationofthefacilitywillbeprovidedinaseparateworkingpaper.Ifanacceptablematchisnotobtained,theanalysisreturnstostepC4andfollowingstepsforcalibrationadjustments.

StepC9:EstimateLOSandReportPerformanceMeasuresThisfinalstepoftheATDMassessmentmethodologyestimatesthereliabilityLOSforthefacility.

StepC9concludesthecomprehensivereliabilityanalysismethodology.

NCHRP03115:ProductionofaMajorUpdatetotheHighwayCapacityManual2010UninterruptedFlowWorkingPaper#3:FreewayMethodologyIntegrationPlanAppendixExistingMethodologyFlowCharts

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AppendixExistingMethodologyFlowCharts

ThisappendixpresentstheexistingoutlinesofHCM2010Chapter10,aswellasthevariousenhancementprojectsforreference.

Figure4:HCM2010Chapter10CoreFreewayFacilitiesMethodology(adaptedfromHCMExhibit1010)


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Step1:InputDataDemand(GP+ML)Geometry(GP+ML)TimeSpace Domain

Step2:Adjustdemandaccordingtospatialandtimeunitsestablished

(ifnecessary)

Step3:ComputeSegmentCapacitiesGPsegmentsusingexistingmethods

MLsegments usingnew/revisedmethods

Step4a:AdjustSegmentCapacitiesEffectsofweather andworkzones

Step4b:CrossWeaveAdjustmentReductioninGPSegment Capacity

resultingfromMLCrossWeaveFlows

Step5:Computed/c ratiosAlllanegroups

Step7:AdjacentFrictionEffectsEvaluateinteraction betweenadjacent

GPandMLlanegroups

Step9:ComputeFacilityMOEsAssignappropriatelevelofservice

Step6a:ComputeUndersaturatedServiceMeasures

Computed foreachlanegroupStep6b:ComputeOversaturatedService

MeasuresComputedfor eachlanegroup

Legend

ExistingHCM2010StepExistingHCM2010StepwithMLmodificationsNewComputationalStepforMLanalysis

Step8:LaneGroupLOSAssignLOStoeachlanegroupconsidering

allfrictionandinteractioneffects

Figure5:ManagedLaneMethodology(adaptedfromNCHRP396DraftHCMChapterExhibit22)


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Figure6:HCM2010FreewayReliabilityMethodology(adaptedfromHCMExhibit3613)

Figure7:HCM2010FreewayReliabilityScenarioGenerationMethodology(adaptedfromHCMExhibit3712)


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Figure8:HCM2010ATDMMethodology(adaptedfromHCMChapter35Exhibit1)

nchrp 03-115 - uninterrupted flow - wp 4 - freeway method integration - 20140415

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