NO_x and PM_2.5 reduction were taken as indicators of emission reduction effect, and vehicle residual value cost, policy implementation cost and fuel cost saving were taken as social cost indicators. Based on social cost of per unit emission reduction (the ratio of social cost to emission reduction), cost-effectiveness analysis was conducted on the effect of the old motor vehicle replacement and subsidy policy in Beijing from June 2011 to December 2020. The results show that the cost-effectiveness of the policy is not monotonically decreasing over the period covered by the study. It shows phased and structural characteristics: the policy is most cost-effective in phasing out diesel trucks and least cost-effective in phasing out China III gasoline vehicles, and the cost of reducing per unit of NO_x and PM_2.5 differs by 14 times and 34 times, respectively; the cost-effectiveness of phasing out small buses tends to decline with the expansion of models to higher emission standards, and the emission reduction potential of small buses with China III and China IV Emission Standards has been limited and the cost-effectiveness is much lower than that under the early policy; the cost-effectiveness of phasing out heavy trucks is better and there are social cost savings in some periods. The paper suggests that the formulation of relevant follow-up policies should be based on cost-effectiveness. It should be cautious about including small passenger cars with higher emission standards in policy implementation, and focus more on the optimization of the policy design for accelerated phase-out of heavy diesel trucks.

以氮氧化物和PM_2.5削减量为减排效果评估指标, 以车辆残值成本、政策执行成本、燃油成本节约为社会成本指标, 借助单位减排产生的社会成本(社会成本/减排量比值), 对北京市2011年6月至2020年12月老旧机动车淘汰更新及补贴政策的实施效果进行成本有效性分析。结果表明, 研究覆盖期内, 该政策的成本有效性并非单调递减, 而是呈现阶段性和结构性特点: 在重点淘汰柴油货车时期, 政策成本有效性最佳, 在重点淘汰国III汽油车时期, 成本有效性较差, 两者氮氧化物及PM_2.5单位污染物减排成本分别相差14倍和34倍; 随着车型拓展到更高排放标准, 淘汰小型客车的成本有效性呈下降趋势, 国III和国IV排放标准的小型客车减排潜力已较为有限, 且成本有效性远低于政策早期; 淘汰重型货车的成本有效性较高, 且在部分时期存在社会成本的节约。建议后续相关政策的制定应基于成本有效性, 审慎地将排放标准更高的小型客车纳入该政策管制范围, 应更关注重型柴油货车加速淘汰的政策设计优化。