Analyzing the spatiotemporal heterogeneity of carbon emissions from road transportation in four Chinese urban agglomerations: An empirical case study

Road transportation has emerged as a major source of carbon emissions contributing to climate change nowadays. Despite extensive research on carbon emissions from road transportation (CRT), few studies focused on comparative analysis of CRT at both the urban agglomeration and city levels, particularly considering variations in development levels. To address this gap, this paper investigates CRT from 65 cities within the four Chinese urban agglomerations—Lanxi, Guanzhong Plain, Central Plain, and Yangtze River Delta— using a top-down framework based upon mode-specific energy consumption intensity. Spatiotemporal characteristics of (per capita) CRT along with the contributing factors are analyzed in which rapid CRT growth with significant spatiotemporal heterogeneity are revealed to form spatial clusters. Based on the contributing factors analysis, at the urban agglomeration level, key factors influencing road transport emissions in the Yangtze River Delta and Central Plain urban agglomerations show significant differences across different periods, reflecting the complex interactions among multiple driving mechanisms. At the city level, the influence factors driving emissions exhibit nuanced spatiotemporal non-stationarity among cities. Moreover, variations in the impact extents of key factors are demonstrated, revealing the dynamic evolution of carbon emission mechanism in different periods and spatial scales. This study offers valuable guidance for policymakers in formulating differentiated mitigation strategies to support low-carbon transport transitions in diverse urban agglomerations.