The National Highway Traffic Safety Administration (NHTSA) and the Environmental Protection Agency (EPA) finalized Phase II fuel efficiency and greenhouse gas standards for medium and heavy trucks in August 2016. These standards follow the Phase I standards set by the agencies in 2011, but are not directly comparable because several test procedures were changed to better reflect real world operation. There are four regulatory categories covered by the new standards: combination tractors (a truck tractor designed to pull a trailer); trailers pulled by combination tractors; heavy-duty pickup trucks and vans; and vocational vehicles (including buses, refuse trucks, and concrete mixers). There are also separate standards for the engines that power combination tractors and vocational vehicles.
For combination tractors, there are individual standards for class 7 day cabs, class 8 day cabs, and class 8 sleeper cabs, each with different standards for low-, mid-, and high-roofs. There are also class 8 heavy-haul standards (with no roof-style differentiation). The fuel economy standards are specified in terms of gallons of fuel used per thousand ton-mile. The carbon dioxide emission standards are specified in terms of grams per ton-mile. The high-roof combination tractor fuel economy standards shown are only one example of the new regulations that are intended to curb medium and heavy truck fuel use and carbon dioxide emissions.
High-roof Combination Tractor Fuel Consumption Phase II Standards, Model Years 2021, 2024, and 2027
Notes: Values were rounded to one decimal place. See final rule for full standard values, exemptions, and exclusions. A combination tractor is a truck tractor designed to pull a trailer.
Note: For heavy-haul tractors, the standard is the same for low-, mid-, and high-roof tractors.