A Study On Traffic Characteristics And Network Indicators Of Arterial System For Linear City

With the rapid development of transportation in China, the overall urban layout has been taking great changes and the differences of the urban characteristics, including urban size, spatial form, land use, transportation framework and trip characteristics have been gradually increasing. However, since "Code for transport planning on urban road" was issued in1995, the indicators for planning urban road network, which mainly classified by the population size, had been guided the construction of urban roads for almost20years. In this period, the applicability of some indicators has aroused much concern. Specifically, the researches for linear city have been conducted, based on the assumption of the relativity between urban spatial form and transportation characteristics. Therefore, the indicators for road network are proposed to be discrepant related to the network form through qualitative analysis and simple data comparison.However, there are some problems showed in these researches, mainly concentrated on two aspects:the lack of quantitative researches and the lack of systematic studies cause the uncertain theories, which cannot put in practice, and only a few typical linear cities could be used for guidance of the urban road construction.Based on the consideration of these issues, this study collects the data of the urban spatial form of658cities in China, including the length, width and the ratio of the length and width (LWR) of the build-up areas. LWR is used to classify cities into three types-round, strip and line,3:1and7:1as the threshold values. Round city is further defined as the Cluster City, while strip and line city as the Linear City. Moreover, urban models are build up considering the urban spatial scale, LWR and road network layout after the urban fabric is abstracted and the arterial road system and traffic characteristics are simplified, followed by traffic assignment with TransCAD. The curves between traffic characteristics and cumulative percent of arterial mileage for two types are simulated, which reveal the differences of traffic characteristics between Linear City and Cluster City. To be specific, the curves present a relatively sharp slope for the Linear and a gentle one for the Cluster, thereby simulating the logarithmic and linear models respectively. This significant difference stems from the shortage for the arterial facility since the space limitation of Linear City, which brings traffic heavily converge on the arterial system.Considering the differences of traffic characteristics for the two type cities, this research proposes the arterial system classification for Linear Cities with different land scale and LWR, and the reasonable correspondence between the ratio of traffic volume and the ratio of artery length of the whole arterial road system. Consequently, these indicators are extended and refined compared with these in the1995’s "Code for transport planning on urban roadd", which accordingly provide reference for arterial network planning and design of Linear City in China.