The construction of transportation infrastructure is an important driving force to promote the sustainable development of Chinese cities. However, the "extensive" and "extensive" urban development mode restricts the sustainable development of Chinese cities. This paper establishes a theoretical hypothesis that transport infrastructure construction affects urban sustainable development, uses the panel data of Chinese cities from 2006 to 2021 to empirically analyze the impact and mechanism of transport infrastructure construction on urban sustainable development, and explores the heterogeneity caused by differences in sample regions and time intervals. The results show that: (1) Baseline regression shows that transport infrastructure construction can significantly promote the improvement of urban sustainable development, and the robustness test using alternative variables and the endogeneity test of instrumental variables support the baseline estimate results. (2) The results of heterogeneity analysis show that the improvement effect of transport infrastructure construction on large-scale cities is greater than that on small-scale cities, the improvement effect of transport infrastructure construction on central and western regions is greater than that on eastern regions, and the improvement effect of transport infrastructure construction on provincial capitals is greater than that on non-provincial capitals. (3) The results of the transmission mechanism show that the improvement of transportation infrastructure construction can promote sustainable urban development by promoting technological innovation and employment scale upgrading. This study further evaluates the economic effects of transportation infrastructure construction and provides empirical evidence for improving urban sustainable development.

In the new stage of China’s economic transformation from high-speed growth to high-quality development, scientific and technological factors have become the new driving force for the high-quality development of China’s economy. Therefore, how the flow of scientific and technological factors affects the high-quality development of regional economy is worthy of in-depth discussion. Based on the panel data of 30 provinces (municipalities and districts) in China from 2006 to 2019, this paper calculates the high-quality economic development index by constructing a comprehensive index system, and empirically examines the direct effect, spatial effect and threshold effect of the flow of scientific and technological factors (including scientific and technological talent factors and scientific and technological capital factors) on high-quality regional economic development. The results show the following: (1) The flow of science and technology talents and science and technology capital is the main driving factor for the high-quality development of regional economy, and the flow of science and technology talents and science and technology capital can play a complementary role. (2) High-quality regional economic development in China presents a certain clustering phenomenon in geographical space. The flow of scientific and technological talent elements and scientific and technological capital elements can stimulate the improvement of high-quality economic development in surrounding areas through the spatial spillover effect of high-quality economic development. (3) Only when the flow of science and technology factors is matched with a higher degree of financial structure and industrial structure can the flow of science and technology factors more effectively promote the high-quality development of regional economy. (4) The higher the level of industrialization and economic development, the more obvious the impact of the flow of scientific and technological talent factors and scientific and technological capital factors on the high-quality economic development. Meanwhile, the lower the degree of marketization, the more obvious the impact of the flow of scientific and technological capital factors on the high-quality economic development.