Study On The Distance Between The Ramp And The Intersection Of Urban Expressway

With the increase in urban population and car ownership,many cities have experienced serious traffic congestion.In order to improve the traffic operation conditions in cities,major small and medium cities have begun to construct expressway systems.The elevated expressway is a relatively closed system,which mainly connected to ground traffic through the ramps.However,the joint between the ramp and the intersection constructed by the current code is short.When there are too many vehicles on the ramp during rush hour,these joints can be troubles in traffic capacity improving and cause even more accidents.Therefore,this paper is of great practical significance on improving the traffic efficiency,reducing traffic congestion,and easing the traffic pressure when it comes to research on reasonable length of the linking section.Based on the existing definition and further analysis,linking section can be divided into three parts in the paper: the merging section,the weaving section and the queuing section.And the paper introduces the weaving situation according to the arrangement types of different ramp ground points.The weaving situation is the most complicated when the ramp is connected to the outermost lane and the vehicles in the linking section can change lanes freely.Taking the most complex connecting segment of vehicle interweaving as the research section,through the traffic investigation,the traffic operation characteristics of each part of the linking section are analyzed.The traffic operation characteristics of the weaving section mainly include the following characteristics and lane changing characteristics,and the lane changing behavior of the weaving section is mostly a mandatory lane changing behavior.Combining the traffic operation characteristics of vehicles in the linking section,the entry ramp length calculation model is built in this paper based on the lane change theory,acceptable gap theory,and queuing theory;the exit ramp length calculation model is established based on the lane change theory,acceptable gap theory,the wave and Webster vehicle delay model.Then,VISSIM software is used to simulate,and the output indicators are compared.From the comparison results,it can be seen that the overall traffic operation status has been greatly improved,which verifies that the calculation model of the linking length is reasonable.