Research On The Relationship Between Traffic Accessibility And Urban Spatial Expansion

The nature of the urbanization process is the expansion of urban space.Under the background of rapid urbanization in China,the problems such as environmental pollution,traffic congestion and waste of public infrastructure are becoming more and more prominent.A city is often along the development of the city road network,transport network can affect the size of the urban development,and will affect the city land utilization.In turn,different land use forms require different traffic arrangements to match.Therefore,the complex interaction between road network and land use in urban expansion has become a hot issue in urban development research.Among them,accessibility is a comprehensive indicator of transportation network,which could reveal the connection and the potential development of regions.Thus,there is a close relationship between evolution of accessibility and urban spatial expansion.Based on the review of foreign and domestic researches,this paper has studied the evolution rules and characteristics of urban spatial expansion in Xi'an from the perspective of transportation accessibility.The coupling relationship between traffic accessibility and urban spatial expansion is analyzed by isochronal superposition method,local spatial autocorrelation and growth regression model.Finally,by selecting the different grades of different roads to quantitatively analyze the spatial effect of urban traffic on urban construction land.The main conclusions are as follows:(1)Since 2000,Xi'an,the rapid development of transport infrastructure,road grade and transportation methods continue to improve.At the end of 2016,the research area has established a "double fast,two-axis,three-ring,eight-ray" fast travel system and a"double fast" road transport system with rail transit as the skeleton.The shortest space distance accessibility pattern of Xi'an is the single center multi-circle structure with the inner wall as the core,and the accessibility index is gradually decreasing outwards.The shortest time distance accessibility evolution pattern presents the center city as the low value center to the periphery along the irregular circle expansion tendency,and along the high directivity is obvious.In 2016,Xi'an has reached a 45-minute city life cycle level,and traffic accessibility has evolved from low-level relative equilibrium-imbalance-advanced relative equilibrium.(2)During the three periods,the average annual growth rate of urban construction land is gradually decreasing,but the difference is gradually narrowing,and the external contour of the city tends to be regular.The intensity of construction land expansion in the study area is changed from medium to low intensity to higher intensity,and there are three obvious high-level centers,and the intensity of urban expansion has obvious spatial correlation and agglomeration;The speed of the expansion of the street to the high value is not high,low value is not low,gradually balanced but the overall decline in the development of the state.(3)The analysis of the distribution curve of the construction land in the four administrative units in 16 years shows that the distribution frequency of the construction land in the six administrative units shows a rapid increase after the rapid increase,and the highest distribution interval of most administrative regions is in the period of 10-20min.In the study area,the expansion of urban construction land and the availability of time reachability are significant.In 2008-2016 years,the growth rate of the four administrative units increased with the increase of the isochronous time,and then increased steadily and then decreased rapidly.(4)By increasing the spatial reachability index and the extended difference index superposition of the grid,the number of high-reach high reachability regions is increasing gradually,and the number of high-expansion low reachability areas is larger.The proportion of the larger area.In addition,the correlation between the reachability and the extension correlation also reveals that the correlation of the extension of the street space is related to its spatial reachability in a large part.(5)According to the results of regression analysis of traffic accessibility and urban spatial expansion,it can be seen that the level of traffic accessibility in 2008 and 2008 has a positive effect on the expansion of construction land in 2008 and 2016 years,and it is better Of the area,the city is expanding faster,but the change in accessibility to the positive impact of the expansion of construction land is weakening.(6)Subway lines and expressways along the construction land has a strong absorption effect,the subway reaction is the most rapid,fast road times,the main road with close absorption effect;outside the road network construction land effect is relatively Weak,and has a strong distance attenuation law,but due to the high-speed and Xi'an main line of the special design,the future of the highway entrance and land has great potential for development.