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ID:240573
大小:55.00 KB
页数:7页
时间:2017-07-12
《公路通行能力和服务水平 毕业论文外文翻译》由会员上传分享,免费在线阅读,更多相关内容在学术论文-天天文库。
1、HighwayCapacityAndLevelsofServiceCapacityDefinedAgeneralizeddefinitionofcapacityis:Thecapacityofanyelementofthehighwaysystemisthemaximumnumberofvehicleswhichhasareasonableexpectationofpassingoverthatsection(ineitheroneorbothdirections)duringagiventimeperiodunderprevailing
2、roadwayandtrafficconditions.Asamplingofcapacitiesformodernhighwayelementsisasfollows:FacilityCapacityinPassengerCarsFreewaysandexpresswaysawayfromrampsandweavingsections,perlaneperhour2000Two-Lanehighways,totalinbothdirections,perhour2000Three-lanehighways,totalineachdire
3、ction,perhour2000Twelve-footlaneatsignalizedintersection,perhourofgreensignaltime(nointerferenceandidealprogression)1800Intreatingcapacity,TRBCircular212dividesfreewaysintocomponents:basicfreewaysegmentsandthoseinthezoneofinfluenceofweavingareasandrampjunctions.Capacities
4、ofexpressways,multilanehighways,andtwo-andthree-lanefacilitiesalsohavethetwocomponents:basicandthoseinthezoneofinfluenceofintersections.Eachoftheseistreatedseparatelybelow.Speed-Volume-CapacityRelationshipsforBasicFreewayandMultilaneHighwaySegmentsAknowledgeoftherelations
5、hipsamongspeed,volume,andcapacityisbasictounderstandingtheplaceofcapacityinhighwaydesignandoperation.Figurel3.1,whichgivessucharelationshipforasinglefreewayorexpresswaylane,isusedforillustrativepurposes.Ifalonevehicletravelsalongatrafficlane,thedriverisfreetoproceedatthed
6、esignspeed.ThissituationisrepresentedatthebeginningoftheappropriatecurveattheupperleftofFig.13.1.Butasthenumberofvehiclesinthelaneincreases,thedriver'sfreedomtoselectspeed7isrestricted.Thisrestrictionbringsaprogressivereductioninspeed.Forexample,manyobservationshaveshownt
7、hat,forahighwaydesignedfor70mph(113km/h),whenvolumereaches1900passengercarsperhour,trafficisslowedtoabout43mph(69km/h).Ifvolumeincreasesfurther,therelativelystablenormal-flowconditionusuallyfoundatlowervolumesissubjecttobreakdown.Thiszoneofinstabilityisshownbytheshadedare
8、aontherightsideofFig.13.1.Onepossibleconsequenceisthattrafficflowwillstabilizeatabout2000vehicle
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