Spatial spillover effects of transportation on carbon emissions in urban agglomerations

Urbanization significantly contributes to global carbon emissions. As urban areas grow and become interconnected, emissions spread across regions due to anthropogenic activities. The transportation system, with its mobility characteristics, exacerbates this spread, resulting in spatial spill-over effects. While previous research often focused on individual cities, this study examines how transportation affects carbon emissions within the Yangtze River Delta Urban Agglomeration (YRDUA), a region in China characterized by rapid transportation development and significant carbon emissions. From 2002 to 2020, carbon emissions in the YRDUA increased by 41.9 %, while disparities between cities decreased by 19.1 %. Using social network analysis and a gravity model, the study constructs a spatial correlation network of carbon emissions, revealing that transportation development exacerbates emissions. The results show a clear core-periphery structure, with core cities acting as outward radiators, and more than tripling in number, and a 13 % increase in inter-city carbon correlation. Notably, cities with well-developed transportation systems act as both “core” and “bridge” nodes in this network, with the “core” degree increasing by 27 % and “bridge” degree increasing by 64 %, while cities with underdeveloped transportation systems remain in the “periphery”. However, this difference is gradually diminishing. The findings emphasize the need for coordinated regional carbon reduction strategies and suggest that strengthening transportation infrastructure between developed and lagging cities could help reduce disparities in emissions and regional carbon output. This study provides a framework for analyzing carbon emissions in other urban agglomerations and underscores the significance of optimizing transportation, promoting low-carbon technologies, and enhancing regional cooperation.