Analysis Of Traffic Flow Characteristic Of Urban Expressway Ramp Entrance

With the accelerating process of city，traffic congestion has become increasinglyprominent and become the bottleneck of economic development．As an important channelconnecting highways and city roads，urban expressway makes great contribution to the citytraffic with high level of service and high-capacity and plays a significant role in alleviatingtraffic congestion．Ramp is the necessary channel of internel flow and external flow interactionin the freeway system，and it combines the main line and other city roads．How it operates affectsthe maximum function of expressway system directly．Taking Xian-yue expressway as studyobject，the entrance ramp was divided into three parts，upstream section，weaving section anddownstream section．Then the traffic flow characteristics and operation mechanism of evolutionof each part were analyzed based on the traffic flow parameters of survey．First of all，according to the path characteristics of urban expressway，this paper expoundedthe basic characteristics of expressway，mainly including the composition and characteristics ofurban expressway，at the same time，the writer analyzed the traffic flow operation characteristicsof different ramp entrance types qualitatively by wave theory．Secondly，basing on the measured traffic flow data of Xianyue expressway in Xiamen city，this paper，in each investigation position，drew the time-varying figures of traffic flowparameters，including flow，speed，density．And the different characteristics of traffic flow foreach part was analyzed，indicating that traffic flow parameters had certain wave characteristicsand was different in different ramp types and observation sections in different traffic conditions，but in weaving and downstream section，its change regulation presented similarity．Finally，according to the measured traffic flow data，this paper established speed-density，flow-density and flow-speed scatter diagram in each ramp section，By the scatter diagram ofmeasured three parameters and data fitting results，relationships curve model was built by datefitting．In the case of going through uncongested to congested traffic states，the writer summedup it existed data gaps，and the relationship between speed and density can be defined linearmodel in all traffic conditions，while for uncongested traffic state the flow and density can be showed by binomial curve and linear trend，but the binomial fitting curve slightly better．Flowand speed would be binomial curve relationship in uncongested traffic state，however in lesstraffic both state，the data would be showed discrete degree，and there was no close relationship．...