武汉城市圈城乡道路网分形的时空结构

构建加权长度-半径分维模型，基于武汉城市圈城乡道路网空间数据，运用GIS空间分析方法，探讨武汉城市圈城乡道路网的密度分形特征及其时空演化规律。武汉城市圈城乡道路网不同程度表现出分形性即具有结构自相似性；不同等级路网的密度分维值普遍遵循距离衰减规律，路网具备较大的扩展潜力；高等级路网发育相对迟缓，由中心向边缘的密度衰减较快，且在分布形态上围绕圈域核心武汉市呈强凝聚态展布；低等级道路则相对发育成熟，分布均匀，覆盖效果较好；不同等级路网的普通和加权长度-半径维数均表现为圈层式结构，遵循中心-外围的距离衰减律；不同时段城乡道路网的分维值不断上升，路网结构渐趋优化，且存在明显的双标度区的双分形结构。

Spatial-temporal structure of capacity fractal about urban-rural road network in Wuhan Metropolitan Area

Transportation network is the material conditions and prerequisites for the formation of the network system in metropolitan areas. It is also the main channel of material flow, energy flow and information flow, which plays an important role in the socio-economic development of metropolitan areas. Based on urban-rural road network (URRN) in Wuhan Metropolitan Area (WMA), this article systematically revealed the fractal features of URRN' s density and its evolution with the application of weighted length-radius fractal model by using GIS spatial analysis methods. The results were obtained as follows. Firstly, the URRN in WMA, to a certain degree, showed the characteristics of spatial complexity and the fractal structure of self-similarity. Secondly, the fractal dimension values of URRN in different grades such as national, provincial, township roads and so on followed the spatial distance decay law. And they were far smaller than the perfect number like 1.702, which showed that the URRN in WMA had a great potential to be improved. Thirdly, the density of URRN with a relatively high grade quickly attenuated from its measuring core to the periphery and represented a strong aggregative distribution pattern around Wuhan city. In contrast, the fractal value of URRN with the low rank grew up slowly, which indicated a strong filling capacity and high level of coverage. Fourthly, both the general and weighted length dimensions of the different URRN grades followed the distance-attenuation law, and they were divided into three spatial parts: core area, transitional area, and marginal area, each with its unique features. Meanwhile, they showed the core-periphery structure and obvious bifractals structure. Furthermore, its value of length-radius fractal dimension continually increased, which indicated that the structure of the road network tended to be gradually optimized.