Quantifying the spillover elasticities of urban built environment configurations on the adjacent traffic CO₂ emissions in mainland China

Urban built environment regulations can effectively mitigate traffic CO₂ emissions. Thus, it is critical to quantify the elasticities of altering built environment configurations. To address this issue, we have built nationwide spatial autoregressive models to differentiate between localized and spillover effects across 325 Chinese cities in the years of 2005 and 2015. Our results indicate that a 1% increase in built-up areas’ size, compactness, and isolation is associated with increases of 0.35%, −0.14%, and 0.13%, respectively, in adjacent traffic CO₂ emissions. The underlying reason is that the spatial configurations of built environment do not only systemically affect the probability, frequency, speed, and distance of intracity motorised travels, but also have impacts on the intercity transboundary mobility of motor vehicles. In addition, the built-up areas’ compactness effect has an antagonistic relation with the per capita GDP effect. Thus, our findings provide evidence that the built environment configuration-related measures can benefit traffic CO₂ emission reductions in adjacent cities. It is therefore necessary for policymakers to make a traffic CO₂ mitigation strategy at the city agglomeration level.