The impact of High-Speed Rails on urban expansion: An investigation using an SDID with dynamic effects method

As a modern transportation system, the opening of the High-Speed Rails (HSR) will deeply influence the economic geography, thus affecting its economic growth and urban development. Based on existing literature, this study examines the impact of the opening of the HSR on the expansion of urban land. We conducted an analysis of Chinese prefecture-level cities via the spatial difference-in-differences (SDID) with dynamic effects empirical strategy for the 2003–2016 period. The result of the opening's impact decomposed from the two dimensions of time and space is meaningful. In the time dimension, the second–sixth years after the opening has a significant impact, and its impact presents a changing trend of first increasing and then decreasing. In the space dimension, urban land growth is promoted in a city that has an HSR line and restrained in the cities that surround it. In the fourth year after the opening, the HSR's impact reached its peak, with an average direct effect of 22.478 km2 and an average indirect effect of −11.729 km2. Therefore, as a man-made infrastructure, HSR will change the existing economic geography pattern. The differences caused by opening the HSR imply the possible occurrence of new development imbalances.