Complexity of Spatial Structure on the Urban-rural Road Network in Wuhan Metropolitan Area
Received date: 2011-06-19
Request revised date: 2011-09-17
Online published: 2012-04-20
Copyright
Studies on the complexity and non-linearity of the spatial structure of road networks have attracted increasing attention during the past several years. However, few efforts have been devoted to the spatial and structural properties of large-scale road networks. In addition, most of current studies focused on either spatial morphology of road networks or structural pattern of road structure, while a comprehensive analysis on the spatial restriction of road network structures is ignored. To fill in the knowledge gap, this article introduces a series of approaches to uncover the spatial influences on the structural characteristics of general road networks. The road network of Wuhan Metropolitan Area (RNWMA) is taken as a case study and the spatial heterogeneity of the structure of RNWMA is analyzed from three aspects with the help of software including ArcGIS9.3, Pajek2.7 and SPSS16.0. Three aspects of spatial heterogeneity of the RNWMA are studied, which are importance of road intersections, accessibility of road intersections and clustering of road intersections. For each property, both statistic analysis and spatial distribution analysis are carried out. Results are visualized by map or chart. Possible explanations are also given. It is found that in the RNWMA: 1) the importance values of roads with high accessibilities in RNWMA follows a power-law distribution, which may indicate that the RNWMA is a scale-free network. While the importance values of roads with low accessibilities follow a Poisson distribution. The co-existence of scale-free and random properties for roads with different accessibility makes the entire road network a complex system with some “emergent” properties; 2) the average length of the shortest path between two roads is relatively large. While the traffic links between two roads in terms of topological distance follow the law distance decay and obvious hierarchy circles can be observed. The spatial convergence of the shortest path length is significantly influenced by roads with high hierarchy (e.g. expressway) and shows perturbation deformation. Two urban transportation corridors, i.e., the Beijing-Zhuhai (north-south) and Yichang-Huangshi (west-east) are observed. Besides, statistically the values of the betweenness of road intersections show exponential distribution although spatially they are relatively even; 3) The clustering coefficient for the RNWMA approaches zero, while several network communities are observed. The spatial distribution for the road intersections with large value of clustering coefficient are “crescent” like, and road intersections with low clustering coefficient values are sparsely distribution in the region. Attempt made in this study will not only help to interpret the structural organization and growth in a limited geographical space, but also shed light on visual analytic means for geographic environments. It is our hope if the findings of this article can provide any alternatives for current road network study, and give practical supports for the construction of urban-rural road network.
LIU Cheng-liang , YU Rui-lin , ZENG Ju-xin , Wang Jia-qi . Complexity of Spatial Structure on the Urban-rural Road Network in Wuhan Metropolitan Area[J]. SCIENTIA GEOGRAPHICA SINICA, 2012 , 32(4) : 426 -433 . DOI: 10.13249/j.cnki.sgs.2012.04.426
Table 1 Relevant indicators of Complex Networks models表1 复杂网络相关指标[23] |
研究内容 | 研究指标 | 公 式 | 涵 义 | 地理意义 |
---|---|---|---|---|
网络节点 重要性 | 度 | (1)Cd(x)=d(x) | 节点i的度ki定义为与该节点连接的其他节点的数目 | 节点对外联系程度 |
度分布 | (2) | P(k)表示的是一个随机选定的节点的度恰好为k的概率 | 节点度值的统计性质 | |
网络节点 可达性 | 平均路径 长度 | (3) | N为网络节点数,dij定义为网络中两个节点i和j之间的距离即连接两个节点的最短路径的边数 | 网络的通达效率 |
紧密度指标 | (4) | dij定义为网络中两个节点i和j之间的距离,该节点到达其它节点的距离之和的倒数 | 网络通达的难易程度 | |
介数指标 | (5) | gjk节点j和k之间的最短路径数,gjk(x)表示节点j和节点k之间经过节点i的最短路径数 | 节点的交通流负载 | |
可达性系数 | (6) Ai=[1/Li+Cc(i)+Cb(i)]/3 | Li为节点i平均路径长度,Cc(i)为节点i紧密度指标,Cb(i)为节点i介数指标 | 节点的可达性 | |
网络节点集聚性 | 聚类系数 | (7) Ci=Ei/[ki(ki-1)/2] | 节点i有n个近邻点,那么这n个节点之间最多有ki(ki-1)/2条连线,以这n个点之间的实际连线数目Ei除以ki(ki-1)得出的值定义为i点的聚集系数 | 节点与相邻节点连接的集聚性 |
Fig.1 Spatial data of the urban-rural road network in Wuhan Metropolitan Area图1 武汉城市圈城乡道路网空间数据 |
Fig.2 The statistical distribution of node degree and cumulative probality图2 道路网节点度分布及累积概率分布 |
Fig.3 Spatial distribution of node degree图3 节点度空间分布 |
Fig.4 Cumulative distribution of node betweenness图4 网络节点介数累计 |
图5 Spatial distribution of closeness |
Fig.6 Spatial distribution of the nodal betweenness图6 节点介数空间分布 |
Fig.7 Spatial pattern of accessibility图7 节点可达系数的空间分布 |
Fig.8 Spatial pattern of the clustering coefficients图8 节点聚类系数空间分布 |
The authors have declared that no competing interests exist.
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