Accelerating Vehicle Fleet Turnover to Achieve Sustainable Mobility Goals: Model and Data

Achieving societal climate goals requires rapid reductions in greenhouse gas (GHG) emissions from transportation. Recent efforts by policymakers have focused on increasing consumeradoption of electric vehicles (EVs). Nevertheless, EV sales remain low. Worse, even if EV market share jumped dramatically, it would take decades to replace the existing vehicle fleet, during which time vehicle GHG emissions would continue, worsening climate change.Consequently, some argue for policies to accelerate the retirement of inefficient fossil-powered vehicles through ‘cash-for-clunkers’ (C4C) programs. We examine C4C policies through a behavioral model of vehicle fleet turnover and EV market development in the U.S. We find C4C policies can substantially reduce vehicle fleet emissions at reasonable cost per tonne of CO2. To meet emissions reductions goals, C4C policies should apply only when consumers replace their fossil-powered vehicles with EVs. C4C policies incentivizing EVs accelerate cost reductions through scale economies, charging infrastructure deployment, model variety, and consumer awareness, boosting EV adoption beyond the direct effect of vehicle replacement. The result is a substantial synergy amplifying the impact of C4C and lowering unit cost of emissions reductions. Cash-for-clunkers is further amplified when deployed together with complementary policies promoting renewable electricity production and a gas tax or carbon price.

实现社会气候目标需要快速减少交通领域的温室气体（GHG）排放。政策制定者近期的工作重点是提高消费者对电动汽车（EVs）的采用率。然而，电动汽车销量仍处于低位。更糟糕的是，即使电动汽车市场份额大幅跃升，替换现有车辆保有量也需要数十年时间，在此期间车辆温室气体排放将持续，加剧气候变化。因此，一些人主张通过“旧车换现金”（C4C）计划来加速低效化石燃料动力车辆的淘汰。我们通过美国车辆保有量更替和电动汽车市场发展的行为模型来研究C4C政策。我们发现，C4C政策能够以合理的每吨CO₂成本大幅减少车辆保有量排放。为实现减排目标，C4C政策应仅适用于消费者用电动汽车替换其化石燃料动力车辆的情况。激励电动汽车的C4C政策通过规模经济、充电基础设施部署、车型多样性和消费者认知加速成本降低，推动电动汽车采用率超越车辆替换的直接效应。其结果是产生显著的协同效应，放大C4C的影响并降低减排单位成本。当与促进可再生电力生产、燃油税或碳价的互补政策一同实施时，旧车换现金计划的效果会进一步增强。