Decoding the drivers of urban road material metabolism and environmental impacts: an integrated MFA-LCA-LMDI analysis of Shanghai, China

Urbanization has accelerated material accumulation in urban road systems, leading to increasing environmental pressures. Existing studies mainly focus on demand-side drivers, while rarely incorporating infrastructure design variables into material stock analysis. Using Shanghai’s road system during 2014–2023 as a case study, this study develops an integrated MFA-LMDI-LCA framework to quantify road material stocks, decompose driving mechanisms, and assess cradle-to-construction environmental impacts. Results show that stocks increased from 416.75 Mt in 2014 to 810.61 Mt in 2023, with larger absolute stocks in outer districts but substantially higher area-normalized stock densities in central districts. Decomposition results indicate that road length effect is the dominant driver, while road width effect partially offsets material stock growth. Environmental impacts, represented by the normalized and weighted ReCiPe 2016(H) endpoint single score (points), increased with material accumulation, including a 20.69% year-on-year increase from 2015 to 2016. The framework clarifies the roles of scale-driven, design-related efficiency and socio-structural factors, and provides new insights for resource-efficient urban infrastructure planning.