In the European Union, CO2 emissions from commercial vehicles grew much faster than from passenger vehicles from 1990 to 2014. Trucks and buses now produce about a quarter of CO2 emissions from road transport in the EU, and that share is growing as emissions from cars and vans decline further to meet increasingly tight CO2 standards. Other major markets—the United States, Canada, China, Japan, and most recently India—have implemented heavy-duty vehicle CO2 standards, and the EU is considering taking that step as well. This study evaluates the cost-effectiveness of long-haul tractor-trailer efficiency technology packages that could become widely deployed in the 2020 to 2030 timeframe, as a contribution to this EU policy dialogue.