Spatial Structure and Evolution of Highway Accessibility in the Yangtze River Delta
长江三角洲公路网络的可达性空间格局及其演化

Based on the highway network map in 1986, 1994 and 2005, choosing weighted mean travel time as indicator, the spatial structure and evolution of major cities highway accessibility in the Yangtze River Delta (YRD) are elaborated in this paper. Considering the characteristics of highway transportation, the impact of accessibility level on city development is also analyzed preliminarily. Some conclusions are drawn as follows. In the 20 years, the spatial structure of accessibility in the YRD has little change; Shanghai, Suzhou and Jiaxing are the center with the lowest accessibility value, and the value increases from the center to the surrounding. The improvement of highway system upgrades the accessibility of major cities in this region, but the evolution takes on different characteristics in the two research stages, and the accessibility upgrade in the second stage (1994-2005) is greater than that in the first stage (1986-1994). The changing extent of accessibility value is related to the initial value, and changing rate of accessibility value decreases from the northern part to the southern at the first stage, but takes on multi-core pattern at the second stage. With the improvement of highway system, the accessibility optimizes from the center to the surrounding. Most cities in this region are above the average level in accessibility, and the city relative accessibility has changed less at the first stage but more at the second stage. Standard deviation analysis of accessibility coefficient shows that the equilibrium of the accessibility distribution descends at the first stage and ascends at the second stage. Considering the highway freight local quotient, the impact of accessibility level on the city development is classified into three categories: promotion, restriction and adaptation. With these results, some suggestions about the development of highway system in this region and some foci for further study are proposed.