江苏省城镇可达性格局演变研究

可达性评价一般包括网络分析、格网分析和栅格分析。借助ArcGIS的空间分析功能，采用栅格分析方法，以江苏省65个县（市）行政中心（城镇）为研究节点，利用江苏省1990、1996、2002和2008年的交通路网数据，对江苏省4个研究年度的城镇可达性进行了分析，并探讨了其格局演变的影响因素。结果表明:江苏省可达性改善明显，整体可达性平均改善高达42.8%。江苏省三大区域可达性改善差异较大，苏南可达性改善最为明显，苏北次之，苏中在整个研究期间均落后于苏南和苏北。总体上，全省区域平均可达性逐步走向均衡，全省交通结构也逐步走向完善。通过分析江苏省高速公路路网建设和可达性之间的相关性可得出结论，即交通建设对区域可达性的影响符合边际效用递减原理，在交通欠发达地区投资的可达性效益要高于交通发达地区。江苏省可达性演变格局在一定程度上反映了城镇发展需求。

URBAN ACCESSIBILITY AND ITS STRUCTURE EVOLUTION IN JIANGSU PROVINCE

The evaluations of accessibility generally include network analysis,grid analysis and raster analysis.With the spatial analysis function of ArcGIS,by the method of grid analysis,to regard the 65 administrative center of counties or cities in Jiangsu Province as the nodes,under the help of traffic network data of Jiangsu Province in the year of 1990,1996,2002 and 2008,the paper analyzed the accessibility of Jiangsu Province for four study years and discussed the influencing factors of the evolution of spatial structure.The conclusions show:①The accessibility of Jiangsu Province has been significantly improved.The average value of accessibility improves up to 42.8%.②The accessibility has improved quite different among north-Jiangsu,middle-Jiangsu and south-Jiangsu.The accessibility of south-Jangsu is improved better than north-Jangsu.Throughout the study period,the accessibility of middle-Jangsu is improved behind the southern-Jangsu and northern Jangsu.③Overall,the regional average accessibility was gradually moving towards to balance,and the traffic structure of Jiangsu Province was going to consummate step by step.④By analyzing the correlation between the construction of highway network and the accessibility,the conclusion can be put forward that the effect of traffic construction is applicable to the principle of diminishing marginal utility.Increase traffic investment in backward areas contributes to the achievement of the regional benefit.⑤The accessibility evolution in Jiangsu Province reflects the demand for urban development.