Research And Application Of Traffic Network Model On Urban Road With Hybrid Petri Nets

With the economy booming, the population and the number of vehicles increase very fast, traffic jams in the cities have become more and more serious, cause more wasting. Because of the limited space for expanding roads in cities, we have to adopt efficient forecast and controlling technology for traffic management. UTS (urban traffic system) is a typical hybrid system, in which the signals are discrete and the traffic flows are continuous. In the paper, we try to model urban traffic system with HPN (Hybrid Petri Net), and we also give some applications of the HPN model of urban system.As a mathematical and graphical modeling tool, HPN has been one of the most important and effective way to model the hybrid system. HPN is a visible modeling tool, which makes us easy to understand, and also the powerful mathematical theory which made us easy to analyze the properties of system. In the paper, traffic system is modeled by HPN, in which the discrete part and the continuous part represent the signals dynamics and traffic flow dynamics respectively. Firstly, the paper shows the basic theory of HPN. Taking the single cross-road as example, we model the two-phase and four-phase with HPN. Finally, taking the four-phase cross-road as example, combining with realistic cross of urban system, we prove the validity of HPN model.We give three examples to illustrate the validity of HPN model of urban crossroad. First we introduce Markov process theory, which can forecast the short-term traffic. Second, we estimate the dynamic traffic flow based on the model. Judging the relative error of traffic flows between HPN and realistic measurements, we can know whether there is extra traffic flows beyond the HPN. Third, HPN can assist in TSS (traffic survey system). When TSS breaks down, it can not control traffic system smoothly. The paper provides a method to solve the problem with HPN model.The research results indicate that the HPN model can fully reflect the hybrid character of UTS. We can use HPN model as a tool to analyze, forecast and control the urban traffic flow.