中国干线公路网络联结的城市通达性

A Study on the Urban Accessibility of National Trunk Highway System in China

以“最短路径模型”为基础,选取距离与时间两个特征指标以及联结两者的速度指标,分析了目前中国国家干线公路网络联结的城市通达性空间格局。结果显示,国家干线公路网络联结的城市呈现明显的“核心—外围”模式,通达性最高的50个城市集中分布在东部的中部地区,通达性最低的50个城市散布在西北、西南、东北等外围地区;通达性空间格局呈现同心圈层结构,由最优区域向外逐渐降低;国家干线公路网络联结的城市通达性空间格局具有显著的边界效应,在不同的速度状态下呈现波状形态变化;国家干线公路网络中行车速度从60￣80km/h的城市通达性变化显著大于80￣100km/h的城市通达性变化;120km/h时速下,8小时以内每个城市连接的城市数量平均为33个,联结数量最多的城市集中分布在东部,平均每个城市可联结数量为70个,联结数量最少的城市分布在西北、西南、东北、东南,平均每个城市可联结数量为6个。未来国家干线公路网络除继续建设外,行车速度的提高将大大影响城市通达性的变化。

Based on the “shortest path matrix”, the selected characteristic indices-distance, time and speed, this paper analyses the current spatial structure of accessibility in the cities which the national trunk highway system connects, and impacts the speed index made. The cities connected by the national trunk highway system turn out the obvious “core-periphery” model with speed index. The top 50 most accessible cities are concentrated in the middle of eastern China, and the bottom 50 ones are located at the periphery such as northwestern, southwestern and northeastern China. The spatial structure of accessibility measured by time index shows a concentric layer structure with attribute falling gradually from interior to periphery. Moreover, the spatial structure of accessibility in cities connected by the national trunk highway system has obvious boundary effect, which shows wave transformation under different speed conditions. The evidence shows that the change in speed acceleration of the national trunk highway system with an urban accessibility of 60-80 km/h is significantly greater than that of 80-100 km/h. For a given city, averaged 33 cities can be reached within eight hours--a normal working day. Most of the cities with the maximum urban access in eighty hours are concentrated in eastern China, averaged 70 cities. The cities with the minimum urban access in eighty hours are located in the northwestern, southwestern, northeastern and southeastern parts of China. Besides further construction, accelerating the speed of the future national trunk highway system will bring about more impacts on the spatial structure of the cities in China.