欢迎来到天天文库
浏览记录
ID:5484462
大小:85.50 KB
页数:7页
时间:2017-12-14
《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)duringagiventimeperiodunderprevailingroadwayandtraffi
2、cconditions.Asamplingofcapacitiesformodernhighwayelementsisasfollows:FacilityCapacityinPassengerCarsFreewaysandexpresswaysawayfromrampsandweavingsections,perlaneperhour2000Two-Lanehighways,totalinbothdirections,perhour2000Three-lanehighways,totalineachdirection,perhour2000Twelve-footlane
3、atsignalizedintersection,perhourofgreensignaltime(nointerferenceandidealprogression)1800Intreatingcapacity,TRBCircular212dividesfreewaysintocomponents:basicfreewaysegmentsandthoseinthezoneofinfluenceofweavingareasandrampjunctions.Capacitiesofexpressways,multilanehighways,andtwo-andthree-
4、lanefacilitiesalsohavethetwocomponents:basicandthoseinthezoneofinfluenceofintersections.Eachoftheseistreatedseparatelybelow.Speed-Volume-CapacityRelationshipsforBasicFreewayandMultilaneHighwaySegmentsAknowledgeoftherelationshipsamongspeed,volume,andcapacityisbasictounderstandingtheplaceo
5、fcapacityinhighwaydesignandoperation.Figurel3.1,whichgivessucharelationshipforasinglefreewayorexpresswaylane,isusedforillustrativepurposes.Ifalonevehicletravelsalongatrafficlane,thedriverisfreetoproceedatthedesignspeed.Thissituationisrepresentedatthebeginningoftheappropriatecurveattheupp
6、erleftofFig.13.1.Butasthenumberofvehiclesinthelaneincreases,thedriver'sfreedomtoselectspeed7isrestricted.Thisrestrictionbringsaprogressivereductioninspeed.Forexample,manyobservationshaveshownthat,forahighwaydesignedfor70mph(113km/h),whenvolumereaches1900passengercarsperhour,trafficisslow
7、edtoabout43mph(69km/h).Ifvolumeincreasesfurther,therelativelystablenormal-flowconditionusuallyfoundatlowervolumesissubjecttobreakdown.ThiszoneofinstabilityisshownbytheshadedareaontherightsideofFig.13.1.Onepossibleconsequenceisthattrafficflowwillstabilizeatabout2000vehicle
此文档下载收益归作者所有