In a few years those kinds of vehicles - school buses, delivery vans, garbage trucks, tractor-trailers and more - will have to get more miles to the gallon than they do today.
The fuel-efficiency plan is expected to be announced Monday in Washington.
The Environmental Protection Agency and the Transportation Department are seeking to improve standards for vehicles sold in the 2014 model year and into the 2018 model year.
The White House has been pushing for tougher fuel economy standards for all kinds of vehicles as a way to reduce oil consumption and cut greenhouse gas emissions.
