Variable Speed Limit Control For Long Freeway Tunnel Entrances And Exits

With the growth in highway mileage, the number of mountain highway tunnel is growing. The construction of the highway tunnel caused a great deal convenient of transportation and economic benefits, which led the city’s economic development. However, due to substantial differences in internal and external environment of the tunnel, which bring a lot of traffic safety hazards, especially in long tunnel entrance section that called accident-prone. In order to improve traffic safety in long tunnel entrance section of freeway, we use traffic flow modeling and simulation as well as variable speed limit to analysis, long tunnel entrance section simulation for tunnel entrances provide basis for implementing variable speed limits and reference in the field.In this paper, we in-depth analysis the cause of the accident in highway tunnel, we found that speeding and bad weather were the main cause of the accident and the speed of vehicles inside the tunnel, the tunnel environment and analysis of the effectiveness of the existing speed limits, determined implementation of variable speed limits in long tunnel entrance section. Previous analysis of highway traffic flow usually uses macro model, which are METANET and CTM. Comparing two macroscopic traffic flows modeling, we decide to use CTM simulation software to the entrance of the long tunnel traffic flow simulation, simulation results show that the CTM model can be a good simulation of long tunnel traffic flow conditions. Selecting variable speed limit the objective function and the constraints of the model which used MATLAB genetic algorithm Toolbox to solve the model.Finally, taking this as the basis, we select Blue high-speed Li-jiahe tunnel which is more than 3km in Shaanxi Province. We use the VISSIM micro-simulation software of secondary development of simulation in free flow and traffic accident cases to evaluate the effect of variable speed limits. Get the following results: compared with the implementation of variable speed limits, after the introduction of variable speed limits, tunnel entrances and adjacent sections of the speed decreases, especially the location of the tunnel entrance and exit speed variation is gentle; in case of traffic accident cases, upstream of the accident vehicle stops and the average travel time is less than 20%, tunnel safety was guaranteed.Simulation results show that the introduction of variable speed limits in long tunnel entrance section not only can reduce the risks of accidents and improve traffic safety, also guarantee driver’s comfort of ride through the long tunnel entrance section, promotes to improve traffic safety, so the variable speed limits should be implemented in long tunnel entrance section.