空间扩容背景下长三角城市群陆路交通联系时空演化

城市群空间扩容有赖于城市间交通联系的强化。文章以县域为研究单元，探讨长三角城市群由16个设区市扩容至26个设区市，各单元经由陆路交通与中心城市及设区市市区的交通联系时空演化。结果显示：(1)空间扩容引致公路通达时间有所增长，但趋于均衡化发展。(2)扩容后普速铁路网络通达时间明显增加，尽管连通度有所提升，但连通强度明显下降；高铁网络通达时间显著低于普铁网络，且连接指数显著高于普铁网络，中心城市在高铁网络中优势突出。(3)主要得益于高速铁路发展，扩容后陆路可达性及其均衡性均有所提升，交通发展很好地支撑了城市群扩容；受城市群扩容及陆路交通发展的共同作用，可达性格局发生了明显变化，长江的阻隔效应更为明显。

SPATIO-TEMPORAL EVOLUTION OF LAND TRANSPORTATION CONNECTION IN THE YANGTZE RIVER DELTA URBAN AGGLOMERATION UNDER THE BACKGROUND OF AREA EXPANSION

Convenient transportation is the base for urban agglomerations to expand area. Taking each county unit of the Yangtze River Delta Urban Agglomeration as the research object, and targeting at the prefecturelevel cities, 16 in 2005 and 26 in 2019, this study comprehensively contrasts and analyses how each object connects with central cities and prefecture-level cities by land transportation to explore how the land transportation connection evolves under the background of urban agglomeration expansion.Conclusionsare as follows: 1) Area expansion of the Yangtze River Delta Urban Agglomeration brings about longer average travel time by highway from research units to central cities and prefecture-level cities. 2) For the railway network of the Yangtze River Delta Urban Agglomeration, there is no tight correspondence between the unit connectivity and intensity. While urban units show higher intensity of connections and denser distribution than county ones, the connectivity of units in research region tends to be less obvious. 3) From the perspective of both highways and railways, in 2005, the average travel time by railway from each county to central cities or prefecture-level cities is in accordance with that by highway network. However, owing to the rapid expansion of high-speed railway network, the situation changes a lot in 2019 when the expansion decreases the average travel time of all the units and improves the balance in the research region.