Research On Urban Traffic Network State Evaluation And Analysis

Traffic congestion has been a global problem and makes serious affects on sustainable development of the city and the living of human beings. To alleviate the negative effect of congestion,it is quite necessary to provide the traffic managers and the travelers with the information on the traffic state timely and reliably. If the traffic network state could be identified accurately,the traffic managers could adopt the effective traffic management and control measures and travelers also could choose reasonable travelling program to reduce the severity of the traffic congestion.A quantitative evaluation model of the traffic network state was established and a new method of traffic network state analysis was proposed based on the evaluation of road network units state (intersections and road sections) by combining the macro road network state evaluation and microscopic traffic state analysis in the article. Four parts work was mainly completed as follows:(1) Urban traffic network state evaluation indicator system was studied. Firstly, three levels of evaluation indicator system structure including traffic network, road sections and intersection, traffic flow parameters was constructed based on analysis of urban traffic network state. Then, the appropriate evaluation indicators were respectively selected according to the different characteristics of intersection, road sections and traffic network state evaluation. Finally, the scientific and reasonable evaluation indicator system of urban road traffic state was designed.(2) The analysis of urban road sections traffic state was studied.The basic characteristics of urban road sections traffic flow was analyed in detail, then mean space speed was selected as the main parameter which could reflect the traffic state of the road sections. The method of the road sections mean space speed estimation based on multi-fixed detector layout was proposed to evaluate the state of road sections. Finally, VISSIM traffic simulation software was used to simulate the traffic state of each road section, which verified the effectiveness of the proposed method.(3) The analysis of urban intersection traffic state was studied. The basic concept of signal controlled intersections was introduced in detail. Then, traffic characteristics of signal controlled intersection was analyzed, three kinds of delay calculation model and traffic wave model for calculating the maximum queue length of the intersection. Finally, three evaluation parameters such as intersection saturation, the mean delay of per vehicle and the maximum queue length were selected and the method of fuzzy reasoning was used to evaluate and analyze the traffic state of the intersection.(4) The evaluation of urban traffic network state was studied. The basic parameters of the traffic network state evaluation such as the intersection entrance saturation and the mean space speed of road sections were put forward based on the analysis of the traffic state of urban road sections and intersections. The traffic network state evaluation function was constructed to measure the overall road network state. Then, the traffic network state coefficient was defined as the traffic flow moving resistance, the critical value of the traffic network coefficient was studied and determined. AHP was used to determine the weight coefficient of each road section and the whole simulated road network state was analyed. Finally, the whole road network state was evaluated and analyed from the side of accessibility and connectivity.