# Promotion Effects of High-Speed Rail on Urban Development: Evidence from Three Lines in China
## 1 Introduction  
Since the world's first high-speed rail (HSR) line began operations in Japan in 1964, the convenience brought by HSR has gained widespread popularity worldwide. According to the \"High Speed Lines in the World 2022\" report by the International Union of Railways (UIC), the total operational mileage of HSR globally has reached 59,498 km. China's HSR operations began with the opening of the Qinhuangdao-Shenyang Passenger Line in 2003. After 20 years of rapid development, the operational mileage has reached 40,493 km, accounting for 68% of the global total. This shows that China has now become a major region for the operation of HSR systems worldwide. At the national level, China has formulated a grand framework plan aiming to integrate major and medium-sized cities into the HSR network. During the planning and siting phase of specific HSR routes, cities along the route aspire to have the line and stations located within their jurisdictions, often leading to competition among cities [1]. For instance, the alignment of the North Yangtze River HSR in Jiangsu Province saw proposals for northern, central, and southern routes due to competition among various cities, with each route passing through different cities. This demonstrates that local governments generally regard the construction of HSR as a crucial task within their regional development strategies. As of now, most provincial capitals and prefecture-level cities in eastern and central China have already achieved HSR operation. For cities along some early lines such as Beijing-Shanghai, Beijing-Guangzhou, and Harbin-Dalian, HSR has been in operation for more than a decade. At the same time, for any local government, the construction of HSR and its supporting projects is a massive undertaking, and its actual impact and benefits after completion cannot be ignored [2]. Therefore, in the current context, it is both necessary and feasible to examine a critical issue: has the initial objective of local governments to promote urban and socio-economic development through the construction of HSR been effective? The study of this issue is not only crucial for China but also holds universal significance for other regions around the world. According to UIC data, an increasing number of countries are committed to making HSR construction a key part of their future plans. Although currently, the operational HSR mileage outside of China accounts for only 32%, the mileage under construction, planned, and in long-term planning, respectively, accounts for 34%, 76%, and 79%. As HSR construction expands in regions such as southeast Asia, south Asia, the Middle East, Africa, and Europe, the benefits of these projects will become a key focus of attention in those areas. Undoubtedly, due to its fast, convenient, and efficient transportation characteristics, HSR significantly promotes the flow of elements such as population and industry. From the perspective of regional coordinated development, the smooth flow of these elements helps to narrow the development gap between developed and underdeveloped regions [3]. For example, [PERSON] et al. (2019) confirmed that the opening of HSR can promote the diffusion of production elements such as capital and technology to surrounding cities, thereby reducing regional development disparities [4]. However, we must clearly recognize that urban development is a complex system evolution process with multiple dimensions, reflected in population agglomeration growth, economic scale expansion, and urban land scale expansion, among other aspects. Additionally, from a physical perspective, the impact of element flows in a region will not be homogeneous; some areas may experience element aggregation, while others may experience element outflow. Therefore, it is necessary to examine the positive or negative impacts of the opening of HSR from multiple perspectives. The most direct impact of the HSR opening is the promotion of population mobility, which subsequently leads to changes in urban residential and employment populations.