珠三角公路网络可达性空间格局及其演化

基于1990、2000和2009年公路网数据，选择空间距离、时间距离和经济潜能３个指标及在此基础上构建综合评价指标，在GIS支持下，探讨1990―2009年珠三角公路网可达性空间格局及其演化规律。研究显示：单一指标不能完整反映公路网综合可达性特征，存在一定局限性。综合评价结果表明：1）研究期内，公路可达性总体上呈现以广―佛核心都市区为最高向外围逐渐递减的圈层结构，可达性最优的核心区范围不断扩大，东西向的可达性递减态势明显快于南北向；2）区域内节点县域可达性等级差异趋于缩小、整体可达性显著提高，但第一阶段（1990―2000年）可达性提高较第二阶段（2000―2009年）更为显著；3）随着路网的逐步完善，东部和南部县市可达性提高明显，中部区域提高幅度低于东、南部县市，西部县市提高较慢。三大地带可达性空间差异明显，中部最高，东部次之，但与中部差异趋于缩小，西部相对最低且与中、东部的差异进一步扩大。

Spatial Pattern and Evolution of Road Network Accessibility in the Pearl River Delta

Based on the road network data of 1990, 2000 and 2009, choosing minimum spatial distance , minimum time distance, economic potential and a comprehensive evaluation index based on those three indices, supported by the GIS software, this paper elaborates the spatial structure and evolution of the road network accessibility in the Pearl River Delta. The research reveals that there are certain limitations in the evaluation of road accessibility based on single evaluation index, which cannot fully reflect the comprehensive accessibility characteristics of road network. Some conclusions from the comprehensive evaluation are obtained as follows: 1) During the study periods, the road network accessibility shows an obvious circle-layer structure and core-periphery structure, and the core area which enjoys the highest accessibility has expanded. The accessibility of Guangzhou-Foshan core metropolitan region is the highest, which then decreasing gradually from this region to the surroundings, and the accessibility decrease in the east-west direction is faster than that in the south-north direction. 2) The gradient difference of counties road accessibility has decreased, and the whole accessibility of counties has improved significantly during 1990-2009, but the accessibility upgrade in the first stage (1990-2000) was greater than that in the second stage 2000-2009). (3) With the gradual improvement of the road network, the accessibility upgrade in the eastern and southern zones is obvious, that in the middle zone is lower, and that in the western zone is the lowest. The accessibility in the middle zone is the highest, the eastern zone ranks the second, and the disparity between the eastern zone and the middle zone has decreased. Whereas, the accessibility in the western zone is the lowest, and the disparity between the western zone and the middle and eastern zones has an expanding trend.