The development of highway infrastructure and CO2 emissions: The mediating role of agglomeration

The development of China's highway infrastructure has led to a rapid increase in carbon dioxide (CO2) emissions while facilitating social and economic development. This paper introduces highway mileage and CO2 emissions into the traditional production density model, using agglomeration as a mediating variable, to theoretically discuss the path through which highway infrastructure influences CO2 emissions. We then use the spatial Durbin model (SDM) to verify the explanatory power of the expanded production density model based on panel data of China's 278 cities from 2003 to 2016. Empirical results indicate that (1) there is an inverted U-shaped relationship between highway infrastructure and CO2 emissions in both local and peripheral cities; (2) highway infrastructure affects local CO2 emissions through the agglomeration pathway but impacts CO2 emissions in peripheral cities mainly through the spatial spillover effect of highway infrastructure; and (3) the U-shaped impact of highway infrastructure on CO2 emissions in western China is diametrically opposed to the results for the east, the central region and the total sample. Therefore, China needs to fully consider the environmental effects of agglomeration to formulate a global emission reduction strategy when building highway infrastructure. Moreover, strategies based on the different stages of highway infrastructure development should be enacted and should be part of a spatially synergistic joint emission reduction mechanism while considering the characteristics of regional development.

Automated summary

The development of China's highway infrastructure has contributed to the increase in CO2 emissions, but the relationship between highway infrastructure and CO2 emissions follows an inverted U-shaped pattern. The impact of highway infrastructure on CO2 emissions differs between local and peripheral cities, with agglomeration and spatial spillover effects playing different roles. Strategies for emission reduction should consider the environmental effects of agglomeration and the characteristics of regional development.