Research On Route Choice And Its Application In Traffic Networks

At present, urban traffic congestion is a hard problem that many countries have to face. And practices have also proven that to build more infrastructures and expand the urban road could not solve this problem thoroughly. Moreover, the utilizable land resource is getting smaller and smaller in big cities. Therefore, in order to provide unblocked traffic environment for travelers, it is necessary to study the methods of transportation management, develop the intelligent transportation technology, take full use of transportation resources, and unearth the potential of traffic facilities. These measures not only improve the function of traffic networks and alleviate the congestion, but also eliminate the obstacles for constructing harmonious society.The paper mainly studies the route choice under different conditions in urban traffic networks. The shortest path problem has been studied for a long time, and some outstanding models and algorithms have generated. But in stochastic time-dependent (STD) networks under different conditions and different requisitions, there are many problems to be improved and solved furthermore. The main contents of this paper are as follows:(1) By analyzing and summarizing the relative literatures of domestic and foreign research on route choice, the shortcomings of them are point out, and some potential areas are found, both of them are regarded as the direction and main contents of the paper.(2) STD networks, compared to static networks, stochastic networks and time-dependent networks, are more coincident with the characteristic of actual traffic networks. Therefore, the route choice in STD networks is discussed in this paper. At first, by adjusting the node search order, the information of each node can be obtained through only one computational step. Based on it, the attributes of a road section are defined as discrete random variables about time. Then, the route choice algorithms, with single attribute and multi-attributes respectively, are proposed for obtaining optimal paths from all nodes to a specified destination. Optimal paths consist of a set of path strategies that enable the traveler to select a direction to his destination at each node in response to knowledge of the arrival time. And the optimal paths are depicted by the tree structure. Moreover, the information entropy theory is used to select synthetic optimal paths with multi-attributes.If the discussed attribute is time only, the paper considers the delay of signal control intersection and analyzes the influence of it to route choice. And according to the concrete arrival time at intersection, the delay is computed.(3) According to the preference of passengers for path and attribute respectively, the paper discusses two models of route choice with multi-attributes in traffic networks. Let the known information be the subjective values, and the preference of passengers be the objective values. Because there are some errors between the subjective and the objective values, two models are set up to minimize it, and the models are solved by the analytic method.(4) In route choice of hazardous materials transportation by road, one of most important questions is the risk assessment, which could ensure the righteous decision-making and safety management in transportation hazardous materials. In this paper, the risk of road section is the synthesis of the casualties, the economic loss and the accident rate. And the three factors are determined by population density, path condition, weather, rank of dangerous and the quality of material etc.. A multiple regression analysis model is established to determine the interdependence between the factors described above, and hypothesis tests are performed. Then by using information entropy theory, the risk forecast model is obtained.(5) The paper applies Ant Colony Algorithm (ACA) to route choice in traffic networks, and some improvements are discussed. Firstly, the path search order is designed. Secondly, by combining the random selection with state transfer probability of Ant Colony, the synthetic state transfer probability is defined. Thirdly, replace the actual length of path by the hypothetical length. Fourthly, the pheromone on routes is dynamic adjusted. Finally, in order to escape from the local optimization, the pheromone of a road section is limited in a range. Based on these, the computational steps of getting an optimal path with single attribute and multiple attributes for specified origin and destination is obtained. In the end, a simulated test is executed.(6) In general, the search of an optimal path is executed in an entire network, but lots of nodes and sections are unnecessary in a real traffic network. If the useless information is deleted from the networks, the computation complexity would be improved. Based on such idea, the degree of a node is defined as a nonnegative integer function, and then the existent conditions of a subset with changed structure are discussed.