Co-benefits of carbon and pollutant emission reduction in urban transport: Sustainable pathways and economic efficiency

The growing demand for urban passenger transportation, driven by economic growth and urbanization, has led to substantial emissions of CO2 and other pollutants. Although significant attention has been given to CO2 reduction, the simultaneous emission of pollutants from similar sources and the benefits of their reduction emissions strategies, both in terms of emissions and economic outcomes, remain underexplored. To address the above concerns, this study has developed an urban passenger transportation emissions system dynamics (UPTE-SD) model, to analyze the economic benefits, emission trends, and synergistic effects of CO2 and pollutant reduction under different scenarios. The results show that: (1) Economic Benefits: CO2 reduction is the primary driver of economic benefits. Among single scenarios, the Transportation structure optimization policy (TSO) scenario performs best, yielding total economic benefits of 9.11 billion RMB. In combined scenarios, the TSO + technological progress policy (TP), promotion of new energy vehicle policy (PNEV) + TSO + TP, and PNEV + TSO + road green space priority development policy (RPD) + TP (composite scenario) exhibit the highest economic benefits, reaching 13.62 billion RMB, 17.04 billion RMB, and 18.44 billion RMB, respectively; (2) CO2 and Pollutant Reduction: For CO2 reduction, TSO is most effective in single scenarios (23.89 %), followed by TSO + TP (36.33 %), PNEV+TSO + TP (41.56 %), and PNEV+TSO + RPD + TP (44.45 %) in combined scenarios. For pollutant reduction, PNEV performs best in single scenarios (29.67 %), followed by PNEV+TSO (38.49 %), PNEV+TSO + RPD (46.38 %), and PNEV+TSO + RPD + TP (49.29 %) in combined scenarios; (3) Synergistic Emission Reduction: In terms of synergistic emission reduction, the best-performing scenarios are RPD in single scenarios, RPD + TP, PNEV+TSO + TP, and PNEV+TSO + RPD + TP in combined scenarios among the recent years. The corresponding synergistic reduction coefficients are as follows: RPD (1.05), RPD + TP (0.99), PNEV+TSO + TP (0.97), and PNEV+TSO + RPD + TP (1.13).