Carbon mitigation potential of metro-based underground urban logistics under operational constraints

Rising urban freight and decarbonization pressures raise an increasingly pressing question: can metros provide green freight mobility without harming passengers? We develop a policy-evaluation framework for metro-based underground logistics (MUL) that integrates multi-task demand forecasting, capacity-constrained freight realization, and emissions accounting under passenger-priority operations. Shanghai's empirical results have showed that freight demand peaks tend to occur outside passenger peaks, while high-volume freight OD flows are less concentrated along major passenger commuting corridors. Under our baseline setting, MUL realizes 66.69% of metro-replaceable demand on weekdays and 92.28% on weekends, with estimated net CO 2 reductions of 14.86% and 24.32%, respectively, after accounting for feeder travel, detours, and unrealized demand. The weekend estimate is more sensitive to freight-demand prediction uncertainty. Scenario comparisons identify station-proximate eligibility, direct routing, off-peak operation, and freight capacity allocation as the main operational levers shaping mitigation.