Scale-free structure of town road network in southern Jiangsu Province of China

From the viewpoint of Graph Theory this paper builds a town road network graph of regional scale, and proposes numerical vertex degree (D-i), rank vertex degree (D-r) and population size vertex degree (D-p) on the base of vertex degree (D). Then the indicators of D-i, D-r, D-p and mathematical statistics methods are applied to investigating scale-free structure of town road networks in the southern Jiangsu Province. The results show that the distribution of Di does not exhibit scale-free properties, but D-r and D-P do. Additionally the correlation coefficient between Dp and Di is only 0.569, but the spatial correlation between Dp and Dr is very evident on the base of correlation analysis and spatial analysis of GIS. The mutual mechanism between D-p and D-r spatially represents a "Core-Belt" model of town development of regional scale. The town development model is open and clustered, and beneficial to both economic development and ecological protection. And then we suggest that Suzhou City, Wuxi City, Changzhou City and Wujin City control towns' high-density pattern by conducting centralization and consolidation policies, and properly controlling and planning higher rank roads; whereas Nanjing City, Zhenjiang City, Jintan City and Liyang City must strengthen the development of towns along higher rank roads.