Traffic Characteristics Analysis And Optimization Control Research For Urban Expressway Ramp

As a result of the growth in traffic demand brought about by the development of the city, urban congestion in expressway came into being by varying degrees. There are many reasons for the expressway congestion, and the ramp setup issue is one of the main reasons.This paper analyzes the main road congestion problems caused by the different ramp types, and selects Chengdu West Third Ring Road for the study. By actual survey, the traffic characteristics of the ramp convergence zone is obtained. And further study is made on the ramp section which may be crowded in certain situation, and the mechanism of exit ramp congestion is concluded through the simulation of different traffic conditions.According to analysis of the characteristics of the object and the traffic simulation, this paper tries to analyze the existing ramp control methods and algorithms and propose the signal control method of the exit ramp the roads. In view of the exit ramp roads control method considering exit ramp influenced by the downstream capacity ramp queuing back overflow phenomenon caused the control. According to the overflow formation mechanism of the research object, control methods for the ramp roads are proposed based on the theory of fuzzy clustering, by divert control strategies, the traffic characteristics of waving area between the entrance and exit ramp was obtained through simulation. By cluster analysis of the simulation traffic characteristics, four different classes of traffic state are obtained. The discrimination of the exit ramp waving area determines the control method.Finally through the programming module-VAP in the induction control module VISSIM, it achieves the simulation of exit ramp roads signal control, and based on this it makes comparison with the stragegy of taking control of the entrance ramp closure. Thus, the results show that the control of the exit ramp roads on the basis of fuzzy clustering could maintain the traffic at a good level, and compared with the other two methods, using the exit ramp roads control tends to be comprehensively better.