Assessing the economic diffusion effects of high-speed rail in China's Yangtze River Delta region through sustainable development indicators

This study aims to investigate the economic diffusion effects of high-speed rail (HSR) development in China's Yangtze River Delta (YRD). The study uses a time-varying difference-in-differences (DID) model and night-time lighting data from 2006 to 2019 for analysis. The analysis reveals that HSR contributes to the spatial reorganisation of economic activity, fostering decentralised growth and regional integration. Contrary to expectations, large cities experienced significant reductions in light intensity, indicating an outward diffusion of economic activity, while small and medium-sized cities saw limited benefits. The findings highlight substantial spatial heterogeneity in HSR's economic impact and underscore potential trade-offs in sustainable urban mobility. While HSR can alleviate urban congestion and support balanced development, it may weaken economic agglomeration in core cities. The study demonstrates the effectiveness of using nighttime lighting as a proxy for urban economic activity and underscores the need for integrated transportation, land use and regional development policies. This research provides actionable insights for policymakers seeking to leverage HSR for inclusive, sustainable urban and regional development.