Research On Congestion Cause And Dissolution Method Of Expressway Tunnle

In recent years,with the vigorous construction of expressways,the number of expressway tunnels has also soared.The opening of expressway tunnels has greatly shortened the travel distance of people,brought great transportation convenience,and promoted the development of national economy.However,as a special section of expressway,the tunnel has lower traffic capacity than the basic section of the expressway due to its internal and external environmental differences.In the case of a large traffic flow,the entrance of the tunnel is susceptible to traffic congestion due to traffic flow conditions,which further reduces the tunnel capacity and is likely to cause traffic accidents.In order to improve the service level of expressway,alleviate the traffic congestion of expressway tunnel and reduce the accident rate of tunnel entrance section,this paper studies the influencing factors and congestion mechanism of tunnels.The research results show that traffic congestion occurs at the entrance of the tunnel when the highway traffic demand exceeds the tunnel’s own capacity,at the same time,traffic waves are transmitted upstream to the vehicle queue.Under such traffic conditions,the vehicle dissipating flow rate at the tunnel is usually lower than the tunnel’s own traffic capacity,that is,the phenomenon of "capacity drop" occurs.In order to solve the traffic congestion caused by excessive long-term traffic demand,this paper proposes a road network diversion method around the expressway,and determines the congestion level by judging the congestion degree of the mainline road,Three types of diversion methods,such as induced diversion,forced current limiting,and mainline forced diversion,are usually used to dissipate the mainline traffic flow.According to research results above,the Er E Shan tunnel of Cheng Zi Lu expressway is selected as the research case.VISSIM is used for simulation of traffic conditions in the case of no variable speed limit and variable speed limit control,and the effect is evaluated.Then,according to the specific situation of the surrounding road network of Cheng Zi Lu Expressway,the specific use of diversion method in actual work is illustrated.