Research On The Structural Characteristics Of Urban Road Network And Their Effects On The Traffic Flow

Urban traffic network, which is regarded as a skeleton of a city, is not only a carrier of social and economic activity, but also the main supporting condition of the city development. However, ever-worsening traffic problems on the one hand have an effect on the economic construction and the operating efficiency of the city; on the other hand do great harm to people’s daily life and work. Therefore, traffic problems have become an urgent matter of the urban sustainable development. It is well known that the urban traffic system is classic, exoteric and complex. Its complexity is embodied not only in the multilevel, variety, large scale and complex structure of the traffic network, but also in dynamic, uncertainty and self-adaption of various traffic phenomenons which make traffic regular pattern extremely complicated. Facing to such a complex huge system, it is necessary to develop in-depth theoretical and applied research on urban traffic problem with the principle of system sciences, interdisciplinary theoretical system and complex system methods. In this way, it is also very dedicated to alleviate traffic problems, build a harmonious transportation system and maintain the normal operation of urban function.In recent years, complex networks theory provides a new viewpoint and method for studying the complex system. The findings of small-world network and scale-free network raise a new revolution of network science, as attracted a great deal of study to complex network. The structure and dynamics of complex network have become two core problems of complex network theory. The network structure can decide the network function; conversely, the network function can influence the evolution of network structure. Urban traffic network is a typical complex network. It is a base research that involves the complexity of topological structure of urban traffic networks with complex network theory. Through the research on network structure, one can find out the inner acting force in the network and driving force to the external, interpret the mechanism and regular pattern of traffic network on a macro scale. These researches will be dedicated to the traffic congestion alleviation and prevention, the spatial-temporal structure planning of a city, disasters prevention and response, reliability improvement of road network. This thesis combines complex network theory with traffic flow theory, and concentrates on the complexity and reliability of traffic network structure, spatial-temporal complexity of traffic network and the influence of traffic network structure on traffic flow. The major contributions are as follows:(1) Based on the complex network theory, the complex network characteristics of two different layout of traffic network are investigated and compared. On the basis, the destruction experiments are done by different methods and the reliability of the two different structures is also further analyzed.(2) According to the interaction of the traffic flow on adjacent roads, a model of road network based on traffic flow is proposed. Then, a new local spatial-temporal autocorrelation coefficient based on adjacency is put forward on the basis of existing spatial-temporal autocorrelation coefficient. A road network model is constructed based on traffic flow. Finally, the spatial-temporal complexity of traffic network is analyzed at both the global and local levels.(3) Combining complex network theory with traffic flow theory, the cell transmission model is used to find the relationship among traffic demand, network structure index and traffic flow state parameters. Then, the traffic carrying capacities in different network structures are further investigated.(4) The spatial-temporal characteristics of the traffic bottleneck roads in two different road network layouts are researched by using the cell transmission model, which include the scale change, congestion duration and velocity change. Then, the structure characteristics of bottleneck roads are further analyzed. Furthermore, the bottleneck intersections are found according to the bottleneck roads.(5) Aiming at four different topological structure networks (i.e. random network, regular network, small-world network and scale-free network), the spatial-temporal correlated characteristics are analyzed by using spatial-temporal correlation theory at a global level.The above work will be dedicated to revealing the operation mechanism of traffic flow, finding the traffic congestion patterns, guiding the planning of road and establishing traffic management policy. Finally, this dissertation summarizes the new findings among the above investigations, and highlights some of valuable issues for further researches in the future.