Research On The Rationality Of The Main City Zone Expressway Scale

Urban expressway, the highest grade road of the urban road network, providing services for the rapid middle and long distance transport, is the urban transportation aorta. The construction of the system of urban expressway network means that the level of urban development is higher. It is not only the key steps to realize the priority development strategy of expressway, but also improve the multi-level road network structure. The urban expressway network scale should coordinate with economy, population and other things. The too fast development of expressway will case the waste of land and money, it even stimulate the growth of traffic demand. The too small network scale will cause serious traffic congestion, decrease the function of expressway and become the obstacle of the city development. The determination of expressway scale in the planning and ascension process is very important. It can help the city to construct expressway, alleviate urban traffic pressure, and promote the rapid development of outlying kilometer. It has very important meanings for urban development.The expressway system basic summary, including content, characteristics and function is researched. The features include auto special, right of way specialization, higher road capacity, relatively independent system and so on. Its basic function including contact each functional area or group, to meet the long distance traffic demand, to separate different traffic, to shield transit traffic, improve the traffic safety and other aspects. It consists of three parts of road, node and ramp. Then the factors influencing the scale of the expressway are researched. The basic principle and the applicability of different calculation methods are elaborated, the supply and demand balance and the regression fitting are chosen for the analysis in the paper. After determining the calculation method of network scale, the steps to determine the network evaluation system is given. Seven main evaluation methods are analyzed, including the advantages, disadvantages and suitable conditions. Considering the research objective and skills, the AHP is chosen. At last, the urban area of Nanjing is the research object, based on the analysis of Nanjing city expressway construct condition, operation situation, congestion, and development environment, the scale was calculated, the lifting scheme is analysis, and the corresponding improvement suggestions are put forward.