长江经济带主要城市群2h出行交通圈格局特征

城市群作为城镇化高级阶段区域社会经济发展和参与国际竞争的主要空间载体,良好的交通通达性是其高质量发展的必要条件。以《交通强国建设纲要》提出的城市群2h通达目标为研究视角,以长江经济带3个国家级城市群为研究对象,选取加权平均出行时间作为测度指标并引入场强和引力模型,对比分析3个城市群所有城市与中心城市两个层级2h出行交通圈格局特征。研究发现：① 3个城市群出行交通圈均表现为从中心向外围地区呈现出由低到高连续扩大的“圈层式”空间格局特征,且长三角和成渝城市群分别形成了“>”字型和“十”字型2h出行廊道,但长江中游城市群尚未形成2h出行廊道。② 城市群中心城市2h出行交通圈的空间分布受区位条件影响较大,越接近区域几何中心则2h出行交通圈覆盖范围越大,而影响腹地受中心城市综合规模的作用明显,3个城市群各中心城市2h出行交通圈和影响腹地的空间分异显著。③ 不同城市群中心城市2h出行交通圈衔接联系水平差异显著,表现出多元的圈层叠加的经济联系格局。④ 高密度高速公路路网在提高城市群中心城市2h出行交通圈衔接联系水平中发挥重要作用,按衔接联系模式特征可将各城市群总结为多中心网络型、多中心组团型与双中心轴辐型。

Spatial pattern of 2h travel circle of major urban agglomerations in the Yangtze River Economic Belt

Urban agglomerations are important carriers to promote the regional socio-economic development and participate in the international competition in the advanced stage of urbanization. And the high traffic accessibility is essential for the high-quality development of urban agglomerations. According to the 2h access goal of urban agglomeration proposed in the Outline of Building a Country with a Strong Transportation Network, taking three national urban agglomerations in the Yangtze River Economic Belt as the study area, this paper employs the weighted average travel time as the measurement index and constructs the field model and the gravity model to comparatively analyze the pattern characteristics of 2h travel circle of all cities and central cities in the three urban agglomerations. The results show that: firstly, the weighted average travel time of all the cities in the three urban agglomerations shows the “circle-type” spatial pattern that continuously expands from low (the center) to high (the periphery). Specifically, the 2h travel corridors exhibits the “>” pattern in Yangtze River Delta urban agglomeration and displays the “cross” pattern in Chengdu-Chongqing urban agglomeration; but Yangtze River Middle Reaches urban agglomeration has not formed 2h travel corridors. Secondly, the spatial distribution of the 2h travel circle of the central cities is significantly affected by the geographical location: the closer to the geometric center of the urban agglomeration, the larger the coverage of 2h travel circle. Moreover, the spatial distribution of the hinterland is affected by the comprehensive scale of the central city. And there are large differences in the spatial distribution of the 2h travel circle and the hinterland among the three urban agglomerations. Thirdly, there are significant differences in the connectivity of 2h travel circle among different urban agglomerations, which shows the pattern of multiple circle superposition and economic connection. The Yangtze River Delta urban agglomeration has initially formed the hierarchical network structure of central cities, while the Yangtze River Middle Reaches and Chengdu-Chongqing urban agglomerations stay at the development stage of connection axis. Fourthly, the spatial arrangement of the transport infrastructure has significant influence on the connectivity of 2h travel circle of the central cities. The high-density expressway network plays an important role in improving the connectivity of 2h travel circle in central cities at the scale of urban agglomeration. From the viewpoint of the structure of connectivity, urban agglomerations can be classified into three types: polycentric-network type, polycentric-cluster type and bicentric-radial type.