Impacts Of High-speed Rail Development On Urban Accessibility And Interactions In China

Advancing accessibility worldwide and eliminating disparities in accessibility is central to the sustainable development goals set out by the United Nations,which generates a metric that can inform the design and implementation of development policies and has renewed international efforts to accurately measure accessibility.As a new means of transportation,the construction of high-speed rail(HSR)will improve accessibility,enhance the aggregate and radiant ability,accelerate the spatial flow of the productive factors,and then promote the economic linkage and socio-economic development among regions.Currently,China had constructed the largest HSR network of the world with the most comprehensive technology,the strongest integration capability,and the highest operating speed.China's "four-vertical and four-horizontal" HSR network provides excellent connectivity among major provincial capitals across the country.According to the new round of the "Mid-to-Long Term Plan for Railway Network" in 2016,China plans to upgrade its "four-vertical and four-horizontal" passenger dedicated lines to"eight-vertical and eight-horizontal" corridor lines.The HSR network,as the national economic artery,critical infrastructure,and major livelihood project in China,will continuously affect the regional and urban development.Although several studies have analyzed the spatial and regional effects caused by HSR,previous studies focused primarily on the impacts of past HSR development,but few efforts have been devoted to examining the potential impact of future development.In addition,existing studies were mainly concentrated in a certain area or a single HSR line,and little attention has been paid to the scale of the nation and urban agglomeration.To address these research gaps,four different spatial scales(region,urban agglomeration,province and city)and four scenarios(without HSR,current network,short-term plan,and long-term plan)were constructed.Based on the analysis of the spatial-temporal evolution of China's HSR network,this study chose accessibility analysis as a cut-in point to evaluate multiscale impacts of the HSR network on spatial and regional effects.Thus,this study aims to answer the following questions:how much does the HSR network improve the level of urban accessibility and interactions?And what extent does the HSR network increase or decrease the disparities of urban accessibility and interactions?The main results are described as follows:(1)Proposing a layered cost distance(LCD)method to calculate door-to-door travel time.The LCD method was proposed,based on a door-to-door approach to real travel time calculations,for detailed and accurate assessment of urban accessibility and spatial interactions.In addition,Google maps were employed to validate the results of travel time calculations by road and HSR travel modes,and the root-mean-square deviation between the two methods is 4.7%.(2)Analyzing the development process and the spatial pattern of the HSR network.The spatial expansion of the HSR network shows a "core-core" pattern at the present and shifts to a "core-network" pattern as the planned HSR network will be implemented.The spatial unevenness in HSR development is evident in that the completed HSR lines are mainly concentrated in the east with the highest population density and economic development.With the expansion of the HSR network,the unevenness of all indicators of the network will be reduced by 43.6%,the connectivity of the network will be improved(an improvement of 37.9%),the interaction of the network will be enhanced(increasing 36.5%).Meanwhile,the topological distance between cities is continuously shortened(a decrease of 26.1%),and the shape of the network will continue to be upgraded(the average degree 36.8%).(3)Evaluating impacts of the HSR network on ground transportation accessibility.A serial of accessibility maps at a spatial resolution of one by one kilometer was created by the LCD method.Accessibility to all cities in China will be improved by approximately 60.8%on average according to the three indicators(weighted average travel time,daily accessibility,and potential accessibility),but the HSR network will not lead to a more balanced distribution in terms of accessibility.The accessibility map exhibits a "core-periphery " structure meaning that the most accessible cities are located in the quadrilateral area of "Wuhan-Zhengzhou-Jinan-Nanjing".Besides,the most notable gains in accessibility will be achieved in the more peripheral locations and HSR cities in central and eastern regions.In addition,in order to maximize the benefits of the HSR development,it will be necessary to focus attention on the inter-city accessibility.(4)Appraised impacts of the HSR network on urban economic linkage.The economic linkage model was improved by using a door-to-door travel time to calculate urban economic linkage.With the construction of HSR lines,the attraction of regional central cities will be continuously strengthened,and the urban economic linkage will be closer among internal cities and external cities in urban agglomerations.The HSR network has been reconstructing the first economic linkage between city pairs,which promotes the accumulative effect of the first economic linkage for HSR cities.Meanwhile,the expansion of the HSR network will also strengthen the first economic linkage between internal cities and external cities in urban agglomerations.The total number of urban economic linkage of all cities in China will increase by about 65.5%after the completion of the planned HSR network,which will produce a more homogeneous total urban economic linkage landscape(an improvement of 12.2%).(5)Assessing impacts of the HSR network on urban hinterland.The field-strength model was improved by using a door-to-door travel time to calculate urban hinterland.The HSR network has been reconstructing the urban hinterland that the disparity of the urban hinterland area will be aggravated among cities(increasing 32.0%).It exhibits a remarkable "polarization effect" where the urban hinterland of cities with high field-strength will expand in size,while the urban hinterland of cities with low field-strength will continue shrinking.There is a great difference between the urban hinterland area and the administrative area,and the HSR network will further enlarge this difference.Thus,it is necessary to focus on the comprehensive impact of the HSR construction on the development of small and medium-sized cities along the HSR lines.In summary,through the multi-time scale and multi-space level measurements and analyses,this study tried to form the unified research framework of the spatial and regional effects caused by HSR by analyzing the development process and spatial pattern of the HSR network,evaluating its impacts on accessibility,urban economic linkage,and urban hinterland,and mapping the results by visualization method.It is expected to serve as a support for policymakers to optimize urban and regional development strategies and related policies.