| Urban road network is not only the skeleton supporting urban development,but also the basic carrier of material activities in the city.The evolution process of urban road network is closely related to the development and change of the city,and the two interact and depend on each other.However,how the road network evolves from the original simple line to the developed and dense traffic network in the long history is not clear,and the traditional road network evaluation index has some limitations in evaluating the network performance.Therefore,this paper takes Gulou area,which has a special road network structure and the most drastic functional changes in Nanjing,as the research object,collects the relevant historical data of the road network within its scope,and carries out the research on the evolution of the road network.Firstly,based on six representative historical periods,this paper tries to restore the real and accurate evolution process of the road network within the Gulou range and reflect the real changes of the spatial structure of the road network.It is found that the development pattern of regional road network has significant historical continuity;The evolution process of road network does not advance at a uniform speed,but has many stages,such as high-speed development stage,stagnation adjustment,renewal and exploration,etc;In recent years,the road network in Gulou area has become stable,and the mode of transportation development has changed to diversification.Secondly,the Box-counting dimension(Hausdorff dimension)and Dendrite dimension in fractal theory are introduced,and the coverage efficiency and differentiation complexity in the development of road network are quantitatively analyzed with the help of the analysis module function of Arc GIS.It is found that the Hausdorff dimension and Dendrite dimension increase unevenly,reflecting that only relying on the encrypted road network can not effectively improve the coverage efficiency;After 1978,the growth of Hausdorff dimension slowed down and the Dendrite dimension even decreased,mainly due to the obstacles of road expansion brought by the closed courtyard in the drum tower area.Finally,based on the Complex Network theory,the road network vector graph is transformed into the form of edge matrix recognized by Gephi analysis software,and the statistical indexes such as node connectivity,network agglomeration and average path length are calculated.Combined with historical facts,explore the leading factors behind the change of indicators.It is found that the average value of road network degree in Gulou area is less than 3.0,and the value of clustering coefficient always hovers around 0.037,both of which are low,which is related to the unique structural form of square grid combined with oblique trunk road in regional road network;The change of the average value of discovery degree is affected by the periodicity of new roads;The average path length tends to be flat after 1978,which is consistent with the results of fractal analysis.To sum up,this paper deeply excavates the evolution characteristics of the road network in Gulou area for more than 100 years,finds and summarizes some important characteristics and laws of the evolution of the ancient city road network,puts forward some suggestions for the planning and construction of the urban road network in combination with the actual situation,and provides reference for traffic organization,urban planning,cultural protection and other work. |
