Twenty-five years of vehicle emission evolution in Beijing: trend, drivers, and validation

Beijing has implemented increasingly stringent vehicle emission control policies over the past decades, establishing itself as a pioneer city in China's green transportation transition. This study developed a comprehensive monthly vehicle emission inventory for Beijing spanning 25 years (2000-2024). Long-term emission trends were decomposed to identify their driving forces and validated against observed concentrations to assess inventory accuracy. During the study period, vehicle emissions of CO, VOCs, NO_x, and PM_2.5 decreased by 93.06%, 83.40%, 50.22%, and 83.75%, respectively. Light-duty passenger vehicles were the dominant contributors to CO and VOC emissions, while heavy-duty trucks accounted for the largest proportion of NO_x and PM_2.5. Decomposition analysis identified emission standard upgrades as the most effective reduction factor (49-67% of total reductions), with vehicle population growth as the dominant driver of emission increases. Monthly patterns exhibited a consistent February trough driven by the Spring Festival holiday and higher autumn-winter emissions due to meteorological conditions. Validation against ground-based NO₂ observations showed strong agreement at both annual (R² = 0.94) and monthly (R² = 0.68) scales. International comparison showed that Beijing's NO_x reduction approached levels in developed-economy cities, indicating that China achieved in roughly 20 years what these regions accomplished over five decades.