Research on The Influence of Transportation Infrastructure on Urban Development Gap in Yangtze River Delta Based on the Difference-in-Difference model

As a significant improvement in the quality of transportation infrastructure, high speed rail significantly improves the regional accessibility and makes the allocation of production factors in a wider range, which has an important impact on urban development. Taking the Yangtze River Delta Urban Agglomeration as an example, this paper uses the Difference-in-Difference model to analyze the impact of high speed rail construction on the urban development gap, which based on the data of prefecture level cities from 2001 to 2018. The results show that the opening of high speed rail is conducive to narrowing the development gap of cities in the Yangtze River Delta. The reason may be that the high speed rail accelerates the trend of industrial transfer within the urban agglomeration, thus promoting the development of regional integration. Secondly, from a local point of view, the polarization effect still exists in the Yangtze River Delta, but the scope of polarization is shrinking, and it gradually moves to the lower level along the gradient of urban development. Finally, the analysis of the lag effect shows that the impact of high speed rail on narrowing the urban development gap is continuous, and with the increasing improvement of the high speed rail network, this impact has a gradually increasing trend, which is of great significance to the balanced development of the Yangtze River Delta.