基于车流波理论的城市快速路出口减速车道设置研究

Research on Deceleration Lane of Ramps Based on Traffic Wave Theory

针对城市快速路出口减速车道设置不合理,高峰期间引起交通冲突增加影响交通安全的问题,通过交通流波动理论对城市快速路分流区减速车道交通冲突产生机理展开研究。分析交通集结波的产生对交通冲突的影响及减速车道长度的关系,通过公式推导计算出交通流波集散时间及集结波长度。为了避免集结波发生的概率及排队长度,应该由高峰时段车流流量、车流速度和密度来确定。以西安市南二环城市快速路为例,使用VIP/T视频交通检测模块对减速车道交通流平峰和高峰时段车道的车流量、车流密度、车头间距和车道占有率进行数据统计及分析,通过研究发现高峰时段城市快速路交通冲突的发生与车流量、车流速度和密度有正相关关系,减速车道的长度可由高峰时段车流量、集结波波速和车流密度确定,同时兼顾排队长度。通过计算,南二环的减速车道长度为188m比目前的实际长40m。

Concerning the problem that unreasonable setting of deceleration lane on urban expressway will increase the traffic conflicts and affect traffic safety,traffic flow fluctuation theory is used to analyze how traffic conflicts happen in divergence areas on urban expressways.It also analyzes influence of traffic queuing wave on traffic conflicts,and its relations with length of deceleration lane.Through formula derivation,it calculates the time of traffic wave gathering and length of the wave.To avoid the occurrence and length of the queuing wave,the traffic flow,speed and density in the rush hour should be used to determine it.Take the South Second Ring Road Expressway in Xi＇an as an example,the VIP/T（video inspection of traffic）module is used to collect and analyze the traffic flow,density,space headway and lane occupancy ratio on the deceleration driveways in both the flat and peak hours of traffic.The analysis finds the occurrence of traffic conflicts on urban expressways in rush hours has positive correlations with traffic flow,speed and density.The length of deceleration lane is determined by the traffic flow,speed of queuing wave and traffic density in rush hours while considering the queue length.The calculation finds length of the deceleration lane on the South Second Ring Road should be 188 m,which is 40 mlonger than its actual length.