Research Of Urban Expressway Traffic Congestion Mechanism And Solutions-a Case Study Of Chongqing Inner-expressway

Urban expressway is the road network of the aorta, having the advantages of large capacity, high speed and high efficiency, which plays an important role in the development of urban traffic. However, along with the increasing of urban economy and the vehicle population, the total traffic demand growing rapidly, the characteristics of urban expressway gradually disappear, and the traffic congestion problems become more serious. Therefore, in order to ease the traffic congestion and improve the efficiency of urban expressway, it is essential to study the mechanism of urban expressway traffic congestion.Firstly, based on analysis the characteristics of urban expressway system, the paper would to analysis the formation of macroscopic mechanism and microscopic mechanism of urban expressway traffic congestion. In the analysis of the macro mechanism of congestion, taking Chongqing as an example, starting from the coordination of city spatial form and layout of the road network, qualitative analysis of the traffic situation, traffic characteristics and the development trend of Chongqing. The analysis shows that it is the convergence of the inner ring expressway and other urban road have congestion cause the congestion of inner ring expressway. Therefore, the paper take the congestion node as the research object to analysis he micro mechanism of urban expressway traffic congestion. In the analysis of the micro mechanism of congestion, it uses the traffic wave model to research the traffic flow characteristics of expressway node. The analysis shows that the combination forms of the entrances and exits node, the interchange form and spacing as well as the form of interchange ramp will have an important effect on the traffic flow operation state of urban expressway.Then, starting from the nodes of urban expressway and other roads to analyze methods of urban expressway congestion mitigation. First of all, the paper builds a model to analysis the spacing of joint entrance and exit. Through the research, the paper gets the minimum spacing model of urban expressway nodes about different nodes entrance and exit combinations, different mainline speed and different mainline flow and puts forward solutions when the spacing is irrational. Secondly, the paper analysis how to select of the form of Grade Separation, and puts forward the selection standards of Grade Separation forms under different topographical features and traffic conditions. And when the traffic conditions changed, in order to ensure the traffic running smoothly, how to transform the Grade Separation. Finally, the paper analysis the interchange ramp forms and width, in order to match the traffic demand as a standard, puts forward suggestions about how to choose the form of ramp and width in different traffic conditions.Finally, taking the inner ring expressway of Chongqing as an example, to verify the proposed method of easing the congestion. First, the paper analysis the current situation of Chongqing inner-ring expressway. Secondly, according to the minimum spacing model, calculates the node Grade Separation minimum spacing of Chongqing inner-ring expressway. It also take the Grade Separation nodes of inner-ring expressway for example, proposes solutions when the spacing unreasonable. Finally, it puts the East Central Grade Separation of Chongqing inner-ring expressway as example to propose the solutions when the ramp set unreasonable.Through the above study, hopes to improve the overall efficiency of urban expressway, providing theoretical basis and practical method to alleviate the problem of traffic congestion of urban expressway.