平均日交通量

Chapter3.Volume,Density&SpeedStudiesandCharacteristics

Volume(rateofflow)---intensityoftrafficmovementSpeed---motionconditionDensity---distributionoftrafficflowoverspaceRelationshipamongthreeparameters---mathematicalequations1.VolumeVolume---isdefinedasthenumberofvehiclesthatpassapointonahighway,oragivenlaneordirectionofahighway,duringaspecifiedtimeinterval,generallyadayoranhour.SomeusefulvolumesAADT(AverageAnnualDailyTraffic年平均日交通量)AAWT(AverageAnnualWeekdayTraffic年平均工作日交通量)ADT(AverageDailyTraffic平均日交通量)AWT(AverageWeekdayTraffic平均工作日交通量)ThesefourvolumesremainatmacroscopiclevelDailyvariationfactor(DF)---isdefinedasratioofAADToveryearlyaveragevolumeforparticulardayofweek(Monday,Tuesdayetc.)

CalibrationofDailyVariationFactorsDayYearlyAverageVolumeforDay(vehs/day)DailyAdjustmentFactorDFMonday1,8201,430/1,820=0.79Tuesday1,5881,430/1,588=0.90Wednesday1,4061,430/1,406=1.02Thursday1,3001,430/1,300=1.10Friday1,2891,430/1,289=1.11Saturday1,2751,430/1,275=1.12Sunday1,3321,430/1,332=1.07Total10,010EstimatedAADT1,430Monthlyvariationfactor(MF)---isdefinedasratioofAADToverADTforparticularmonthoftheyearCalibrationofMonthlyVariationFactorsMonthTotalTraffic(vehs)ADTforMonth(veh/day)MonthlyVariationFactor(MF)January19,840/31=640797/640=1.25February16,660/28=595797/595=1.34March21,235/31=685797/685=1.16April24,300/30=810797/810=0.98May25,885/31=835797/835=0.95June26,280/30=876797/876=0.91July27,652/31=892797/892=0.89August30,008/31=968797/968=0.82September28,620/30=954797/954=0.84October26,350/31=850797/850=0.94November22,290/30=743797/743=1.07December21,731/31=701797/701=1.14Total290,851AADT=290,851/365=797veh/dayHourlyvolumesandpeakhourvolume（小时流量，高峰小时流量）Hourlyvolumesareusedtoreflectvariation(fluctuation)oftrafficvolumeinaday

PeakhourvolumeisdefinedasthevolumeinthesinglehourthathasthehighesthourlyvolumeRateofflow

(流率）---definedasanequivalenthourlyvolumeforagiveninterval(intervalcanbe5,10,15minutes)usedindesigntoreflecttheworstscenariousedinmodelingmathematicalrelationshipamongparametersinresearchgenerallytheshortertheintervalthehighertherateofflowIntervalVolumeIntervalVolume7:00–7:05157:30–7:35177:05–7:10257:35–7:40357:10–7:15187:40–7:45287:15–7:20427:45–7:50327:20–7:25317:50–7:55267:25–7:30187:55–8:0020V5=(180,300,216,504,372,216,204,420,336,384,312,240)V10=(240,360,294,312,360,276)V15=(232,364,320,312)MaxV5=504;MaxV10=360;MaxV15=364

Hourlyvolume=307Peakhourfactor

（高峰小时系数）---isdefinedastheratioofhourlyvolumedividedbymaximumrateofflow

PHFisusedtoreflectthefluctuationofvolumedistributioninanhour!!!PHF5=307/504=0.61;PHF10=307/360=0.85;PHF15=307/364=0.84;Peak-Hour-Factor(PHF)The30thhourlyvolume

(第30位小时交通量)---definedasanhourlyvolumeatwhichitsrankingonyearly-countingcurvecounts30thamong8760hourlyvolumesinayearDDHV(DirectionalDesignHourlyVolume设计小时流量)---DDHV=AADTⅹKⅹDwhere:Kisproportionofdailytrafficoccurringduringthepeakhour,expressedasadecimal;Disproportionofpeak-hourtraffictravelinginthepeakdirection,expressedasadecimalD=ratioofdesignhourvolumeinthemajordirectiontothetotal(方向性系数）K=ratioofdesignhourvolumetothe24hourvolume（设计小时系数）RelationshipBetweenDDHVandAADTIngeneralDandKis

constant!!!VMT(VehicleMilesTraveled=车英里)orVKT(VehicleKilometersTraveled车公里)---definedasaproductofnumberofvehiclesandmiles(orkilometer)traveledbythesevehiclesEstimationofVehicle-MilesTraveledonaLimitedNetwork:AnExampleStation8-HourCount(vehs)LinkLength(mi)LinkVMT(veh-miles)A6,9670.251,741.7515,1590.251,289.7525,2540.251,313.5035,8200.251,455.0044,0580.251,014.5058,7100.252,177.5067,2740.251,818.50NetworkTotal10,810.50PCEandPCU

（小汽车当量）---definedasthenumberofpassengercarsdisplacedbyonetruck,bus,orRVinagiventrafficstreamTrafficintensitycanbeusedascriteriontodeterminepassengercarequivalent2.SpeedTimemeanspeed(TMS，时间平均车速)---definedastheaveragespeedofallvehiclespassingapointonahighwayoversomespecifiedtimeperiod

Spacemeanspeed(SMS，空间平均车速)---definedastheaveragespeedofallvehiclesoccupyingagivensectionofahighwayoversomespecifiedtimeperiodTMSisapointmeasure,whileSMSisameasurerelatingtoalengthofhighwayorlaneSMSisoftenusedintrafficflowtheorystudyatmacroscopiclevelwhileTMSisusedforengineeringstudyTMS≥SMSAveragetravelspeedandaveragerunningspeed

（平均行程，行驶速度)---Averagetravelspeed=distance/traveltimeAveragerunningspeed=distance/runningtimeRunningtime=traveltime-stoppeddelays

Operatingspeed

（运营速度）---definedasthemaximumsafespeedatwhichavehiclecanbeconductedinagiventrafficstream,withoutexceedingthedesignspeedofthehighwaysegment.CriticalspeedorOptimalspeed

(临界车速)---definedasthespeedatwhichmaximumflowrate(capacity通行能力)canbeachieved(oratwhichgasconsumptionofvehiclesisatthelowest)

Percentilespeeds

（百分位速度）---isaspeedbelowwhichthestatedpercentofvehiclesinthetrafficstreamtravel

Intrafficengineering,85thpercentilespeedisoftenusedasameasureofthemaximumreasonablespeedforthetrafficstream(upperlimit),whilethe15thpercentilespeedmaybeusedasameasureoftheminimumreasonablespeedforthetrafficstream.The50thpercentileormedianspeedisusedtodescribethemidpointofthespeeddistribution.

3.DensityItisdefinedasthenumberofvehiclesoccupyingagivenlengthofhighwayorlaneandisgenerallyexpressedasvehiclesperkilometerperlane.Difficulttoobtainfromthefield---usingoccupancy(占用率）whichisdefinedastheproportionoftimethatadetectoriscoveredbyavehicleinthespecifiedperiodoftimeCloselyrelatedtotrafficdemandItiseasyfordriverstoperceiveSpacing(车头间距）andheadway（车头时距）

spacingisdefinedasthedistancebetweensuccessivevehiclesinatrafficlane;headwayisdefinedasthetimeintervalbetweensuccessivevehiclesastheypassapointalongthelaneDifferentdensityonbothdirectionsoffreeway,USAFreewayofI-15inSanDiego,USADifferentdensityoneachdirectionofexpressway,BeijingDifferentdensityonbothdirectionsofmainstreet,BeijingItshouldbenotedthatdensityandvolumearedifferent.Theformerrepresentsdistributionofvehiclesintermsofspaceoccupyingtheroadway;whereasthelaterexpressesthefrequencyofvehiclespassingapointofroadway.4.Relationshipamongvolume,speedanddensity

Thisequationisvalidforuninterruptedflowonly!!!TheGreenshieldslinearmodel

GraphicalRelationshipAmongThreeParametersCongestionZoneGreenberg’slogarithmicmodel

Underwood’sexponentialmodel

NorthwesternUniversityModel

SummaryNameofmodelMustknownParameterNotesGreenshieldsuf,kjuf,betweenspeedlimiuf,anddesignspeedkjishardtoestimateGreenbergu0,kjuf,isinfiniteUnderwooduf,k0koishardtoobserveuneverreacheszerokjisinfiniteNorthwesternuf,kjkjisinfiniteuwillbeneverzeroDerivationofflow-speedandflow-densityrelationshipsunderGreenshields

CapacityCapacityisdefinedasthemaximumrateofflowthatcanbeachievedonroadwayfacilitiesunderprevailingroadway,traffic,andcontrolconditions.Similarlywecanget:

ThreeimportanttrafficstatesFreeflow(uf,q=0,k=0)Optimastate(qmax,u