Mechanism And Simulation Of Traffic Congestion In Freeway Tunnel

In recent years, with the rapid development of freeway construction, especially freeway construction in the mountainous area, the number of freeway tunnels has maintained a rapid growth trend. Besides, with the development of the economy, traffic volume of the freeway tunnel has continued increasing, and traffic congestion phenomenon has became more and more prominent. Traffic congestion also could induce traffic safety, environmental pollution, the increase of travel time, the increase consumption of energy and other issues, therefore, studying the generation, propagation and dissipation mechanism of the traffic congestion in freeway tunnel will have great theoretical and practical value to alleviate traffic congestion, in improving traffic safety situation, reducing environmental pollution and improving traffic management in the tunnels.The generation, propagation and dissipation mechanism of the traffic congestion in freeway tunnel was studied by using traffic wave theory and cellular automata model. The detailed contents were as follows:① The causes of traffic congestion in freeway tunnel were analyzed from five aspects, including drivers’ characteristics, the features of the vehicle, the environment in the tunnel, road conditions and traffic accidents.② The aggregation and dissipation processes of recurrent traffic congestion and occasional traffic congestion in the freeway tunnel were studied on a macro level. Traffic flow characteristics were studied by using traffic wave theory when recurrent congestion or sporadic congestion in freeway tunnel occurred.③ In the NS model, all vehicles follow the same random slow probability p, which are quite different from the actual traffic situation. In reality, the random deceleration probability of the current vehicle is affected by the vehicle in front. According to this phenomenon, the random slow rule in the NS model was improved in this paper, and the freeway tunnel was divided reasonably, thereby a cellular automata simulation model which was aimed to simulate freeway tunnel traffic congestion was established.④ Take Zhongliangshan tunnel on Chengyu Expressway as the recurrent congestion simulation case, and take Youyang Taohuayuan tunnel as sporadic congestion simulation case. Through the use of cellular automata simulation model established in this paper and MATLAB simulation software, under different simulation conditions, the evolution of freeway tunnels recurrent traffic congestion and occasional traffic congestion were studied, moreover, the occasional traffic congestion simulation results were subjected to a comparative analysis with the results produced by using traffic wave theory.This paper presents a traffic congestion simulation model based on cellular automata, which can calculate maximum queue length of congestion、congestion time and other parameters, and it will have an important reference value on the afterward study of the mechanism of freeway tunnel traffic congestion.