Fuzzy evaluation of traffic flow stability based on the discreteness of traffic parameters

Abstract

The microscopic traffic flow stability is difficult to describe the influences of the dynamic relationship between vehicles on traffic conditions. In order to solve the problem, from the perspective of macroscopic and microscopic parameters of traffic flow and considering the discreteness of velocity and following distance, the paper selected average velocity, average following distance, the variation coefficient of velocity and following distance as the traffic flow stability indices. And a stability evaluation model was constructed based on fuzzy theory. Using VISSIM simulation software, simulation experiment was carried out. The influences of traffic volume, traffic incident, traffic signals and GPS permeability on traffic flow stability evaluation were analyzed. Results show that traffic flow stability decreases gradually with the increase of volume. When there is a traffic incident, traffic flow stability decreases at the upstream section, while it is contrary to the downstream section. With the decrease of GPS permeability, the differences of the four indices and traffic flow stability at these GPS permeability with that of full permeability are becoming bigger and bigger. So the behavior described by the model is consistent with the actual state of the traffic system, proving that the model is real and effective. Thus it can be used to evaluate urban traffic flow stability macroscopically.