Relevant features that define how quickly the US can decarbonize passenger vehicles include the rate of stock turnover, defined as how quickly new vehicles replace scrapped used vehicles, and emissions from electricity production. Using 2002-2020 passenger vehicle registrations data, we document features suggesting that stock turnover has slowed down over time. We then build a stock turnover model to assess how this finding and expected electricity grid decarbonization affect future paths of greenhouse gas (GHG) reductions. We find that at current rates of stock turnover, only moderate GHG reductions are likely by 2030, but large reductions are possible by 2050. This result is robust to a range of assumptions for future grid decarbonization, which has surprisingly little effect on future passenger vehicle emissions. Our results motivate designing policies to accelerate stock turnover for the purpose of achieving near-term decarbonization targets.
