Researches On Traffic Assignment Problem For Trunk Highway Network Of Shandong Province

The economy of our country has been improved a lot during these years. As one of the pillar industries that cannot be separated from economic development, the transportation industry has experienced rapid development. Provincial trunk highway networks are important parts of the comprehensive transport system. And planning for them has always attracted extensive attention. At present, the U.S. Federal Highway Administration BPR impendence model is widely used during the traffic assignment procedure for provincial trunk highway networks, kind of which only considers a single factor that impacts traffic volumes of links. In addition, the procedure usually gets results without regard to the impact that arises from the hierarchy of the network, which will lead to many questions.The paper studied common traffic assignment models based on the theory of traffic assignment. Advantages and disadvantages of the models that had been introduced were also presented. On the level of provincial trunk highway network planning, disadvantages of the widely used BPR function were analyzed. After that, the basic form of the trunk highway network impendence model was given as the combination of travel time and money cost. The travel time budget model which takes the travel time uncertainty into account was used as the travel time function. And the money cost function considered both the cost of vehicle operation and road tolls. Last of this part, the model was demarcated separately from the aspects of highway and normal trunk highway with the method of maximum likelihood, using the data collected from the trunk network of Shandong Province.In the second part, the hierarchy of the network was taken into consideration. Researches had been done on the kinds of path that users will use during a trip. The route choice behavior was also been studied by using the logit route choice model. After that, a multi-level traffic demand distribution model was promoted to distribute the total travel demand into every sub-level network of the whole one, so that the total demand had become the demand matrixes of sub-level networks. This step can make the assignment result more close to the fact.Afterwards, the theory of user equilibrium model and the equilibrium condition had been studied. Considering the non-additive path based cost function, the equilibrium condition with non-additivity had been proposed. In order to solve the model, researches had been done on possible solution algorithms. And the self-adaptive gradient projection algorithm was adopted to solve the model. Finally, some numerical experiments were conducted by constructing some networks of different styles, using the data collected from the trunk network of Shandong Province.From the results of experiments, it indicates that comparing with the methods that are widely used for provincial trunk highway network planning at this stage, the research findings of this paper do make the results of traffic assignment much closer to the real situation, with most of the possible influencing factors taking into account. The results of the research provide a possible method for the traffic assignment procedure of Shandong provincial trunk network planning. This will make sense for improving the rationality and reliability of the provincial trunk highway network traffic assignment results.