Vehicle electrification is one of the primary strategies being pursued for the decarbonization of the transportation sector. But to meet emissions reduction goals for that sector, the current vehicle replacement rate is insufficient. Vehicle scrappage policies can accelerate fleet turnover by providing an incentive to retire a vehicle before its natural end of life and simultaneously replace it with a more efficient or less polluting alternative. Previous scrappage programs, like the United States' Cash for Clunkers, have had limited success as decarbonization policies; however, most of these programs ended before the widespread availability of electric vehicles and did not have decarbonization as a primary policy goal. Here we explain why scrappage policies may be necessary to meet climate goals, review historic vehicle scrappage policies from a variety of countries, highlight the successes and failures of those policies, and establish policy design considerations that could help ensure that future scrappage programs are more successful than previous efforts.