Analysis of the influence on expressway safety of ramps

As the very important parts of the expressway system, on and off ramps have a great effect on the operation effect of expressways. Once congestion occurs at on and off ramps, it will directly affect the safety of the expressway and vehicles. So this paper first analyzes the location design of on ramps, the length and the influences on the expressway running state of off ramp downstream traffic state, and establishes the expressway operation models based at on and off ramps. The expressway operation models include off ramp delay model, on ramp delay model, expressway delay model and side road delay model under the influence of the distance between on and off ramp and traffic volume. At the same time, the paper analyzes the connection between the traffic operation state and traffic safety, and establishes the expressway safety model based on congestion degree. Through simulation verification, the impact of on and off ramp on the security of the expressway is analyzed. In the simulation, safety rank division is simulated to verify and safety index of different safety ranks. Finally the paper concludes that the delay caused by traffic of the on and off ramps can decrease the safety of expressway.