Highway Capacity Manual 2010, Volume 2

358 Pages·2010·6.85 MB·English

HCM2Q1Q
HIGHWAY CAPACITY MANUAL
VOLUME 2: UNINTERRUPTED FLOW
TRANSPORTATION RESEARCH BOARD
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HighwayCapacityManual2010
VOLUME 2
UNINTERRUPTED FLOW
OVERVIEW
Volume2oftheHighwayCapacityManual(HCM)containssixchaptersthat
presentanalysismethodsforuninterrupted-flowroadways—thatis,roadways
thathavenofixedcausesofdelayorinterruptionexternaltothetrafficstream.
Thisvolumeaddressesthreetypesofuninterrupted-flowroadways:
(cid:127) Freeways,definedasseparatedhighwayswithfullcontrolofaccessand
twoormorelanesineachdirectiondedicatedtotheexclusiveuseof
traffic;
(cid:127) Multilanehighways,definedashighwaysthatdonothavefullcontrolof
accessandthathavetwoormorelanesineachdirection,withtraffic
signalsorroundaboutsspacedatleast2miapartonaverage;and
(cid:127) Two-lanehighioays,definedasroadwayswithonelanefortrafficineach
direction(exceptfor occasionalpassinglanesortruckclimbinglanes),
withtrafficsignals,roundabouts,orSTOP-controlledintersectionsspaced
atleast2miapartonaverage.
TheHCMtreatsroadwaysthathavetrafficsignals,roundabouts,orSTOP-
controlledintersectionsspacedlessthan2miapartonaverageasurbanstreets.
UrbanstreetsarediscussedinVolume3,InterruptedFlow.
VOLUME ORGANIZATION
VOLUME2:UNINTERRUPTEDFLOW
Freeways 10.FreewayFacilities
11.BasicFreewaySegments
Trafficentersandexitsafreewayviaramps.Chapter13,FreewayMerge 12.FreewayWeavingSegments
andDivergeSegments,focusesonlocationswheretwoormoretrafficstreams 13.FreewayMergeandDiverge
Segments
combineto formasingletrafficstream(amerge)orwhereasingletrafficstream 14.MultilaneHighways
dividestoformtwoormoreseparatetrafficstreams(adiverge).Theselocations 15.Two-LaneHighways
aremostcommonlyramp-freewayjunctionsbutincludepointswheremainline
roadwaysjoinorseparate.Chapter13canalsobeappliedinanapproximateway
toramp-highwayjunctions onmultilanehighwaysandcollector-distributor
roads.Ramp-streetjunctions areanalyzedwiththe methodsintheintersection
andinterchangechaptersinVolume3.
Sometimesfreewaymergesarecloselyfollowedbyfreewaydiverges,ora
one-laneoff-rampcloselyfollowsaone-laneon-rampandthetwoareconnected
byacontinuousauxiliarylane.Inthesecases,thetrafficstreamstoandfromthe
rampsmustcrosseachotheroverasignificantlengthoffreewaywithouttheaid
oftrafficcontroldevices(exceptfor guidesigns).Theterm"closely"impliesthat
thedistancebetweenthemergeanddivergesegmentsisnotsufficientforthem
tooperateindependently,thuscreatingaweave. Chapter12,FreewayWeaving
Segments,providesproceduresforanalyzingweavingoperationsonfreeways.
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HighwayCapacityManual2010
Itcanbeappliedinanapproximatewaytoweavesonmultilanehighwaysand
collector-distributorroads,butnottoweavesonarterialstreets.
Theremainingportionsof thefreewaymainlinethatarenotmerge,diverge,
orweavingsegments(exceptfortollplazas,drawbridges,orsimilarpoints
wherefreewaytrafficmaybetemporarilyrequiredtostop)arecoveredin
Chapter11,BasicFreewaySegments.Thischapteralsoprovidesinformationon
thebaseconditionsandpassengercarequivalentsforheavyvehiclesthatare
commontoallofthefreeway chapters.
Chapter10,FreewayFacilities,providesamethodologyfor analyzing
extendedlengthsoffreewaycomposedofcontinuouslyconnectedbasicfreeway,
weaving,merge,anddivergesegments.Suchextendedlengthsarereferredtoas
afreewayfacility.Inthisterminology,thetermfacilitydoesnotrefertoanentire
freewayfrombeginningtoend;instead,itreferstoaspecificsetofconnected
segmentsthathavebeenidentifiedfor analysis.Inaddition,thetermdoesnot
refertoafreewaysystemconsistingofseveralinterconnectedfreeways.
ThemethodologiesofChapters11,12,and13allfocusonasingletime
periodofinterest,generallythepeak15minwithinapeakhour.However,
Chapter10'smethodologyallowsfor theanalysisofmultipleandcontinuous15-
minperiodsandiscapableofidentifyingbreakdownsandtheimpactof such
breakdownsoverspaceandtime.
MultilaneHighways
Chapter14,MultilaneHighways,presentsanalysismethodsfor the portions
ofmultilanehighwaysawayfromtheinfluenceofsignalizedintersections(or
otherformsofintersectiontrafficcontrolthatinterrupttheflowoftrafficonthe
highway).Manymultilanehighwayswillhaveperiodicsignalizedintersections,
eveniftheaveragesignalspacingiswellover2mi.Insuchcases,themultilane
highwaysegmentsthataremorethan2miawayfromanysignalized
intersectionsareanalyzedwiththeChapter14methodology.Isolatedsignalized
intersectionsshouldbeanalyzedwiththemethodologyofChapter18,Signalized
Intersections.
Bicyclesaretypicallypermittedonmultilanehighways,andmultilane
highwaysoftenserveasprimaryroutesforbothcommutercyclists(onsuburban
highways)andrecreationalcyclists(onruralhighways).Chapter14presentsa
methodforestimatingthebicyclelevelofservice(LOS)onmultilanehighways.
Two-Lane Highways
Chapter15,Two-LaneHighways,presentsanalysismethodsfortheportions
oftwo-lanehighwaysthatareawayfromtheinfluenceofintersectiontraffic
controlthatinterruptstheflowoftraffic.Ingeneral,anysegmentthatis2.0to3.0
mifromthenearestsignalizedintersection,roundabout,orintersectionwhere
thehighwayisSTOP-controlledwouldfitintothiscategory.Wherethese
interruptionstotrafficarelessthan2.0miapart,thefacilityshouldbeclassified
asanurbanstreetandanalyzedwiththemethodologiesofChapter16,Urban
StreetFacilities,andChapter17,UrbanStreetSegments,whicharelocatedin
Volume3.
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HighwayCapacityManual2010
Chapter15canbeusedtoanalyzethreeclassesoftwo-lanehighways:
» ClassIhighwaysareoneswheremotoristsexpecttotravelatrelatively
highspeeds,suchasmajorintercityroutes,primaryconnectorsofmajor
trafficgenerators,dailycommuterroutes,ormajorlinksinstateor
nationalhighwaynetworks;
(cid:127) ClassIIhighwaysareoneswheremotoristsdonotnecessarilyexpectto
travelathighspeeds,suchashighwaysservingasaccessroutestoClassI
facilities,servingasscenicorrecreationalroutes,orpassingthrough
ruggedterrain;and
(cid:127) ClassIIIhighwaysareonesservingmoderatelydevelopedareas,suchas
portionsofaClassIorClassIIhighwaypassingthroughsmalltownsor
developedrecreationalareasorlongersegmentspassingthroughmore
spread-outrecreationalareas,withincreasedroadsidedensities.
Two-lanehighwaysoftenserveasroutesforrecreationalcyclists.Chapter15
presentsamethodforestimatingthebicycleLOSonthesehighways.
RELATEDCHAPTERS
Volume 1
ThechaptersinVolume2assumethatthereaderisalreadyfamiliarwiththe
conceptspresentedintheVolume 1chapters,inparticularthefollowing:
(cid:127) Chapter2,Applications—typesofHCManalysis,typesofroadwaysystem
elements,andtrafficflow characteristics;
« Chapter3,ModalCharacteristics—variations indemand,peakandanalysis
hours,K-andD-factors,facilitytypesbymode,andinteractionsbetween
modes;
9 Chapter4, TrafficFlowandCapacityConcepts—trafficflowparametersand
factorsthatinfluencecapacity;and
® Chapter5,QualityandLevel-of-ServiceConcepts—performancemeasures,
servicemeasures,andLOS.
Volume 3
Theintersectionandinterchangechapters(Chapters18-22)areusedto
determinetheoperationsof freeway ramp-streetjunctions andtheoperationsof
isolatedtrafficsignals,roundabouts,andSTOP-controlledintersectionsalong
multilaneandtwo-lanehighways.InthecontextofVolume2,itisparticularly
importanttoexaminethelengthofthequeueextendingbackfromafreewayoff-
ramp-streetjunction, sincelongqueuesmayaffectfreewayoperations,a
situationthatisnotaccountedfor intheHCMtechniques.
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HighwayCapacityManual2010
Volume4
VOLUME4:APPLICATIONSGUIDE FivechaptersinVolume4(accessibleatwww.HCM2010.org)provide
MethodologicalDetails
additionalinformationthatsupplementsthematerialpresentedinVolume2.
25. FreewayFacilities:
Supplemental Thesechaptersareasfollows:
26. FreewayandHighway
Segments:Supplemental (cid:127) Chapter25,FreewayFacilities:Supplemental—detailsofthecomputations
27. FreewayWeaving:
usedintheChapter 10methodology,andcomputationalengine
Supplemental
28. FreewayMergesand flowchartsandlinkagelists;
Diverges:Supplemental
35.ActiveTrafficManagement (cid:127) Chapter26,FreewayandHighwaySegments:Supplemental—examplesof
CaseStudies
applyingalternativetoolstosituationsthatarenotaddressedbythe
TechnicalReferenceLibrary
Chapter11methodforbasicfreewaysegments,andstate-specificdefault
valuesforheavyvehiclepercentagethatapplytoallVolume2chapters;
(cid:127) Chapter27,FreewayWeaving:Supplemental—examplesofapplying
alternativetoolstosituationsnotaddressedbytheChapter12method;
(cid:127) Chapter28,FreewayMergesandDiverges:Supplemental—examplesof
applyingalternativetoolstosituationsnotaddressedbytheChapter13
method;and
(cid:127) Chapter35,ActiveTrafficManagement—descriptionsofactivetraffic
managementstrategies;adiscussionofthemechanismsbywhichthey
affectdemand,capacity,andperformance;andgeneralguidanceon
possibleevaluationmethodsfor activetrafficmanagementtechniques.
AccessVolume4at TheHCMApplications GuideinVolume4providesthreecasestudiesonthe
www.HCM2010.org
analysisofuninterrupted-flowfacilities:
(cid:127) CaseStudyNo.3illustratestheprocessofapplyingHCMtechniquestothe
analysisofatwo-lanehighway;
(cid:127) CaseStudyNo.4illustratestheprocessofapplyingHCMtechniquestothe
analysisofafreeway;and
(cid:127) CaseStudyNo.6illustratestheapplicationofalternativetoolstoafreeway
facilityinasituationwhereHCMtechniquesareunsuitable.
CaseStudiesNo.3andNo.4focusontheprocessofapplyingtheHCM
ratherthanonthedetailsofperformingcalculations(whichareaddressedbythe
exampleproblemsintheVolume2chapters).Thesecasestudies'computational
resultsweredevelopedbyusingHCM2000methodologiesandthereforemay
notmatchtheresultsobtainedfromapplyingtheHCM2010.However,the
processofapplicationisthefocus,notthespecificcomputationalresults.
TheTechnicalReferenceLibraryinVolume4containscopiesof (orlinksto)
manyofthedocumentsreferencedinVolume2anditssupplementalchapters.
BecausetheChapter10methodologyistoocomplextobeimplementedby
manualpencil-and-papertechniques,theFREEVAL-2010spreadsheethasbeen
developedtoimplementthe methodology'scalculations.TheTechnical
ReferenceLibrarycontainsacopyofthespreadsheetalongwithauser'sguide.
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HighwayCapacityManual2010
LEVELSOFANALYSISANDANALYSISTOOLS
AsdiscussedinChapter2,Applications,HCMmethodologiescanbe
appliedtotheoperations,design,preliminaryengineering,andplanninglevels
ofanalysis.Theselevelsdifferbothintheamountoffielddatausedinthe
analysis(asopposedtodefaultvalues)andinthewaytheHCMisapplied
(iteratively,tofindadesignthatmeetsadesiredsetofcriteria,orasasingle
application,toevaluateperformancegivenaparticularsetofinputs).Each
Volume2chapterprovidesasectionthatdiscusseshowtoapplythechapterto
thesedifferentlevelsofanalysis,alongwithasectionwithrecommendeddefault
valuesfor planningandpreliminaryengineeringanalyses.
ThreeVolume2chapters(10,14,and15)providegeneralizedservicevolume
tablesapplicabletofreewayfacilities,multilanehighways,andtwo-lane
highways,respectively.Thesetablescanbeusedforlarge-scaleplanningefforts
whenthegoalistoanalyzealargenumberoffacilitiestodeterminewhere
problemsmightexistorariseorwhereimprovementsmightbeneeded.Any
facilitiesidentifiedaslikelytoexperienceproblemsorneedimprovementshould
thenbesubjectedtoamoredetailedanalysisthattakesintoaccounttheexisting
orlikelyfuturecharacteristicsofthespecificfacilitybeforeanydetaileddecisions
onimplementingspecificimprovementsaremade.Becausetheservicevolumes
providedinthesetablesarehighlydependentonthedefaultvaluesassumedas
inputs,itisrecommendedthatuserswishingtoapplygeneralizedservice
volumetablesdeveloptheir owntablesbyusinglocaldefaultvalues,in
accordancewiththeprocessesdescribedinAppendixAandAppendixBof
Chapter6,HCMandAlternativeAnalysisTools.
Chapter6alsodescribesingeneraltermstheconditionsunderwhichtheuse
ofalternativetoolstosupplementHCMcapacityandquality-of-service
proceduresshouldbeconsidered.EachVolume2chaptercontainsasection
discussingthepotentialapplicationofalternativetoolstothespecificsystem
elementaddressedbythechapter,andChapters26-28inVolume4provide
exampleproblemsillustratingapplicationsofalternativetoolstoaddressHCM
limitations.Eachchapterliststhespecificlimitationsofitsmethodology.The
majorlimitationsaresummarizedasfollows:
(cid:127) Freeways
o Operationsofoversaturatedfreewaysegments(butnotnecessarily
oversaturatedfreewayfacilities,asdiscussedlater)
o Multipleoverlappingbreakdownsorbottlenecks
o Conditionswhereoff-rampqueuesextendbackontothefreewayor
affectthebehaviorofexitingvehicles
o Operationofseparatedhigh-occupancyvehicle(HOV)facilitiesand
weavinginteractionsbetweenHOVandgeneral-purposelanes
o Tollplazaoperations
o Ramp-meteringeffects
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HighwayCapacityManual2010
(cid:127) Multilanehighways
o Operationsduringoversaturatedconditions
o Theimpactsofshoulderparkingactivity,busstops,orsignificant
pedestrianactivity
o Possiblequeuingimpactswhenamultilanehighwaysegment
transitionstoatwo-lanehighwaysegment
o Differencesbetweenvarioustypesofmedianbarriers,andthe
differencebetweentheimpactofamedianbarrierandatwo-wayleft-
turnlane
o TherangeofvaluesusedtodevelopthebicycleLOSmodel(although
themodelhasbeensuccessfullyappliedtoruralmultilanehighways,
usersshouldbeawarethatconditionsonmanyofthosehighwaysare
outsidetherangeofvaluesusedtodevelopthemodel)
(cid:127) Two-lanehighivays
o Operationsduringoversaturatedconditions
o ImpactofintersectiontrafficcontrolontheoverallfacilityLOS
o TherangeofvaluesusedtodevelopthebicycleLOSmodel(although
themodelhasbeensuccessfullyappliedtoruraltwo-lanehighways,
usersshouldbeawarethatconditionsonmanyofthosehighwaysare
outsidetherangeofvaluesusedtodevelopthemodel)
Ifananalysisofanindividualfreewaysegmentrevealsthesegmenttobe
oversaturated,thenChapter10,FreewayFacilities,mustbeusedtoassess
operationofthesegmentanditsimpactsonupstreamanddownstreamsections.
IftheChapter 10analysisrevealsthattheoversaturationwouldextendbeyond
thegeographicortemporalboundariesoftheanalysis,thentheboundariesofthe
Chapter10analysisshouldbeexpandedtocontaintheoversaturation.If
expandingtheboundariesoftheanalysisisnotpractical,thennoanalyticaltool,
includingtheHCM,cangiveacompleteanswerinthissituation.
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