常规干线公交网络空间方向分布及结构特性分析方法

A Method for Analyzing the Distribution of Spatial Orientation and Structural Characteristics of Trunk Bus Network

空间结构合理的常规干线公交网络可以帮助城市提升公共交通服务效率,缓解道路交通压力。为深入分析城市常规干线公交网络空间结构特性,使用公交网络GIS信息嵌入拓扑结构模型的方式开展研究。借鉴道路网空间信息测度方法,基于香农熵理论提出公交线路方向熵和公交网络方向熵分析方法。根据提取的公交网络拓扑结构中相邻站点间线路段的空间方向信息,使用方向熵测度得到公交线路及网络空间方向分布情况。在现有的规范及研究中,选取并拓展能够体现公交线网空间结构特性的指标,与方向熵组成常规干线公交线网空间结构分析指标体系,从线路和网络2个层面出发探究常规干线公交网络空间方向分布并分析其结构特性。以哈尔滨市63条常规干线公交组成的网络为例进行分析。网络空间方向分布结果表明:公交网络方向熵为2.84,大于网络内任意单条线路方向熵。验证得到公交线路方向熵的测度结果与线路的实际情况相符,方向熵可以有效量化公交线网拓扑结构的空间方向分布;在指标间的相关性方面,公交线路方向熵与公交线路长度的相关性最高,公交线路站点对重复系数与公交刷卡数的相关性次之。网络结构特性分析结果表明:哈尔滨市63条常规公交干线组成网络的平均集聚系数为0.467,网络中节点度分布的数据拟合度为0.978,表明该网络是1种具有择优发展倾向的网络,网络结构较稳定。基于香农熵的分析方法,为描述公交网络空间方向分布情况提供了新的思路;对网络结构特性的分析,为常规干线公交线网规划提供理论参考。

Trunk bus network(TBN)with a reasonable spatial structure can improve the efficiency of urban public transport services,and reduce traffic congestion on roadways.In order to analyze the characteristics of spatial struc-ture of urban TBN,this paper develops a method by analyzing GIS information of bus network with a topological structure model.Referring to the previous method for analyzing spatial characteristics of road network,a method for calculating the orientation entropy of bus lines and that of bus networks is proposed based on the Shannon entropy theory,respectively.According to the spatial orientation of bus lines between adjacent stations extracted from its to-pological structure of a TBN,the distribution of spatial orientation of bus lines and networks is measured by their orientation entropy,respectively.Based on the existing standards and studies,the indicators that can reflect the char-acteristics of spatial structure of bus networks are selected and then combined with orientation entropy to develop a set of evaluation indicators for analyzing spatial structure of TBN.Then,the distribution of spatial orientation and the characteristics of the network structure of TBN are analyzed at the following two levels:line and network.A case study is conducted for the bus network consisting of 63 trunk bus lines in the City of Harbin.Regarding the distribution of spatial orientation of TBN,experiment results show that the orientation entropy of the TBN is 2.84,which is greater than the orientation entropy of any single line within the sample.It is verified that the measured ori-entation entropies of the bus lines are consistent with their observed patterns.The orientation entropy can effectively quantify the distribution of spatial orientation of the topological structure of bus network;In addition,it is found that the correlation between the orientation entropies of bus lines and the length of bus lines is the highest,followed by that between the repetition coefficient of adjacent bus stations and the number of smart cards used at those sta-tions.In the respective of the characteristics of network structure,experiment results show that the average coeffi-cient of concentration of the TBN consisting of 63 lines in the City of Harbin is 0.467,and the goodness-of-the-fit of the distribution of nodes in the network is 0.978,indicating that the network has a tendency of preferential devel-opment,and the network structure is relatively stable.In conclusion,the proposed method based on the Shannon en-tropy provides an alternative way to describe the distribution of spatial orientation of bus network and can be used to support the planning of the TBN.