Application of Three-phase Traffic Flow Theory Based on Vissim

The study of evolution mechanism of traffic flow condition is an important part of traffic flow theory.This paper studies the evolution mechanism of traffic flow condition in urban freeway based on the different traffic loads in urban freeway section.Unable to carry through the massive traffic survey,the paper uses Vissim simulation software to simulate the change of traffic flow characteristics in different traffic volumes.According to the statistical analysis of simulation data,this paper analyzes the traffic flow characteristics in different traffic conditions and defines the threshold for traffic condition transition and the value area of each traffic condition with density.The result shows that the traffic flow presents different conditions under different traffic load,namely free flow,synchronized flow and wide moving jam flow.