过江通道对乡镇可达性影响分析

过江通道建设将缩短相关城镇到中心城市的时间距离，提高乡镇可达性水平，改善区位条件，从而带动乡镇经济发展。为了定量地评价过江通道对乡镇可达性和城镇体系影响，以苏通大桥为例，借助GIS软件，采用成本加权栅格方法，选取加权平均旅行时间指标、潜力模型与场强指数，对比分析通车前后乡镇可〖JP+1〗达性空间格局与中心城市腹地和场强空间变化。结果表明：南通东部与大桥北岸乡镇可达性与区位优势潜力显著提高，城镇整体可达性与区位优势潜力小幅提高。可达性空间格局变化较小，可达性值呈现出长江以南由东向西递增，江北由西南向东北方向递增特征。大桥影响范围更多限于南通东部县市与大桥北岸。城镇空间体系变化较小，腹地与场强变化多出现在大桥两岸，场强值分布呈西南向东北方向逐渐递减的分异特征。数据表明大桥优化了南通东部区位条件，使其更好地接受发达地区产业与知识的“溢出效应”，加快苏南产业向南通东部地区转移，促进区域均衡发展。

ANALYSIS ON THE IMPACT OF THE CROSS YANGTZE PASSAGE ON TOWNS' ACCESSIBILITY ——A CASE OF SU TONG BRIDGE

The construction of the Cross Yangtze Bridge will improve the 〖JP2〗level of related towns’ accessibility〖JP〗 and better towns’ location condition by reducing time distance between town and main city,which drive towns’ economic development.In order to quantitatively evaluate the effect of the bridge on the towns’ accessibility and the urban system,we took Su Tong Yangtze Bridge for examples 〖JP2〗and select the accessibility〖JP〗 indicator,the potential model and field strength index to analyze towns’ accessibility spatial pattern and town system in study area before and after Su Tong Yangtze River Bridge opened to traffic by using the cost weighted distance analysis in geographic information system.The result indicates that the significant changes in location advantage potential and accessibility take place in eastern Nantong and near the bridge.The overall towns’ level of accessibility and location potential advantage have some growth in study region.Smaller change takes place toward the whole town accessibility spatial pattern after the bridge were completed,which shows accessible value growth trend from east to west in the south of the Yangtze River and from west to east in the north of the River.Small change occurs in town spatial system and the most change exists near both sides of the bridge.The overall field strength shows gradually decrease from south west to north east in study area.The above conclusion indicates that the bridge optimize the location conditions of the eastern Nantong, which make towns in their region more quickly and comfortably accept the developed regions “spillover effect” of industry and knowledge,speed up industry of the southern Jiangsu transfer toward eastern Nantong and promote to balance regional development