Report Investigates Fuel Economy for Medium- and Heavy-Duty Vehicles

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A. Sue Weisler

James Winebrake

A new congressionally mandated report from the National Research Council evaluates various technologies and methods that could improve the fuel economy of medium- and heavy-duty vehicles, such as tractor-trailers, transit buses and work trucks. Currently, there are no fuel efficiency standards for such vehicles, which account for about 26 percent of the transportation fuel used in the United States.

The study was produced by the council’s Committee on an Assessment of Fuel Economy Technologies for Medium- and Heavy-duty Vehicles, which includes James Winebrake, professor and chair of the Department of Public Policy at Rochester Institute of Technology.

“Medium-and heavy-duty vehicles are an extremely important component of our national transportation system and have a major impact on our overall environmental footprint,” notes Winebrake, who is also co-director of RIT’s Laboratory for Environmental Computing and Decision Making. “Improving the efficiency of these vehicles can improve environmental quality, reduce petroleum dependence and decrease costs to operators.”

In 2007, Congress passed legislation requiring the U.S. Department of Transportation to establish fuel economy standards for medium- and heavy-duty vehicles. The National Highway Traffic Safety Administration asked the National Research Council to recommend the best ways to measure and regulate fuel economy for these vehicles and assess technologies that could improve it.

In the report, the council argues that regulators should use a fuel consumption measure that accounts for the amount of freight or passengers carried by these vehicles. The miles-per-gallon measure used to regulate the fuel economy of passenger cars—light-duty vehicles—is not appropriate for medium- and heavy-duty vehicles, which are designed above all to carry loads efficiently. For example, a partially loaded tractor-trailer could travel more miles per gallon than a fully loaded one, but this would not be an accurate measure of the fuel efficiency of moving goods.

Instead, any regulation of medium- and heavy-duty vehicles should use a measurement that reflects the efficiency with which a vehicle moves goods or passengers, such as gallons per ton-mile, a unit that reflects the amount of fuel a vehicle would use to carry a ton of goods one mile.

“A potential obstacle to fuel economy standards for medium- and heavy-duty vehicles has been how to measure economy given the different applications of this vehicle class compared to passenger cars,” says Winebrake. “By measuring efficiency instead of simple miles-per-gallon, a realistic metric can be created that reflects actual vehicle performance under real-world conditions.”

In addition, the report recommends nontechnical methods the government could use to lower fuel consumption, including providing incentives to train vehicle operators in efficient driving techniques, which could result in fuel savings of anywhere from 2 percent to 17 percent.

Copies of the report are available from the National Academies Press website.