A Study on the Urban Accessibility of National Trunk Highway System in China

Based on the shortest path matrix, the selected characteristic indices-distance, time and speed, this paper analyses the current spatial structure of accessibility in the cities which the national trunk highway system connects, and impacts the speed index made. The cities connected by the national trunk highway system turn out the obvious core-periphery model with speed index. The top 50 most accessible cities are concentrated in the middle of eastern China, and the bottom 50 ones are located at the periphery such as northwestern, southwestern and northeastern China. The spatial structure of accessibility measured by time index shows a concentric layer structure with attribute falling gradually from interior to periphery. Moreover, the spatial structure of accessibility in cities connected by the national trunk highway system has obvious boundary effect, which shows wave transformation under different speed conditions. The evidence shows that the change in speed acceleration of the national trunk highway system with an urban accessibility of 60-80 km/h is significantly greater than that of 80-100 km/h. For a given city, averaged 33 cities can be reached within eight hours--a normal working day. Most of the cities with the maximum urban access in eighty hours are concentrated in eastern China, averaged 70 cities. The cities with the minimum urban access in eighty hours are located in the northwestern, southwestern, northeastern and southeastern parts of China. Besides further construction, accelerating the speed of the future national trunk highway system will bring about more impacts on the spatial structure of the cities in China.