基于二分网络的北京公交线路布局的空间依赖性

公交网络运行系统的结构性缺陷常常致使其成为城市交通拥堵的罪魁祸首。传统公交网络空间研究皆将其视为一个独立的交通运输方式,忽视了城市道路网形态与结构的内生作用。本文基于二分网络的思想,通过构建公交线路—城市道路的空间依赖矩阵,引入系列空间依赖度测度指标从局域、全局两个尺度探讨了北京市的公交线路的空间依赖度及依赖的核心空间,并通过社团识别对北京市公交线路的依赖空间进行了划分。结果发现：① 局域依赖度方面,北京市公交线路布局高度依赖度少数城市主干道和城—郊区快速干道,其空间依赖格局形成了以市中心为核心,以城—郊区快速干道为通道的中心—外围的廊道扩散格局;② 全局依赖度方面,北京市公交线路空间布局结构失衡,比较脆弱,受城市道路路面路况影响较大,同时以四环为模糊边界的市中心区域成为北京市公交线路依赖的核心空间;③ 依赖空间划分上,北京市公交线路布局与城市地域空间呈现良好的对应性,朝阳、海淀、三环内（东城和西城）是公交线路布局规模最密的3个区域。

Spatial dependency of bus-line distribution based on bipartite network: A case study of Beijing city

As the subnet is derived from and supplied by urban road network, public transport network (PTN) owes its maximum development to the development level of urban road network. The structural defects of PTN often make itself the culprit of urban traffic congestion. Traditional research on spatial distribution of PTN tends to regard PTN as an independent mode of transportation, but overlooks the endogenous effect of urban road network’s morphology and structure. Based on the idea of binary network, this paper discusses the local and global spatial dependency of Beijing bus-line distribution by constructing the space correlation matrix between bus-line and city road and introducing dependency measures from 1-mode network. This endeavor also divides the dependence space of Beijing bus-line by community detection with the help of the software named Ucinet 6. We find out that in terms of local dependence, the layout of bus-line is highly dependent on a few city trunk roads and expressway connecting downtown and suburb, so its spatial dependence pattern becomes a corridor diffusion pattern of core-periphery, which takes the downtown as the core and the rapid suburban corridors as the channel. In terms of global dependence, the unbalanced distribution structure of bus-line seems more fragile and is greatly influenced by the city road traffic conditions. Meanwhile, the downtown area bounded by the Forth Ring becomes the core space of bus-line dependence. In terms of space division, the layout of Beijing bus-line presents good correspondence to the city districts. To exemplify this, Chaoyang District, Haidian District and the area within the Third Ring Road have the densest bus-line distributions.