A recent report from the National Research Council will help guide the federal government as it develops fuel-economy and carbon regulations for medium- and heavy-duty trucks.

Congress is looking at this group of previously unregulated vehicles because they use 26% of the liquid transportation fuel consumed in the U.S., and their energy consumption is projected to continue rising for the next 25 years. The 414-page report shows that combining such technologies as advanced diesel engines, hybrid powertrains, improved aerodynamics, low-resistance tires and others could improve fuel economy in work vehicles by as much as 50% by 2035.

The cost of installing fuel-saving technologies would add about $15,000 to a heavy-duty pickup truck and $85,000 for a Class 8 tractor-trailer—or an incremental cost of as much as 52%. However, the added fuel efficiency would recoup the cost over the vehicle’s life, the report notes.

Carbon-dioxide and other greenhouse-gas emissions are directly proportional to fuel consumption.

Measuring fuel efficiency will be more complex for this segment than for cars and light trucks because of the differences in work modes. For example, a tractor-trailer’s efficiency might be measured in gallons per ton-mile traveled. Developing similar standards for various off-road vehicles, if ever established, will be even more challenging, industry experts say.

Improving fuel efficiency helps clean the air by cutting greenhouse gas put into the atmosphere. As the amount of greenhouse gas a vehicle emits is directly proportional to the amount of fuel it burns, fuel efficiency will be key to meeting carbon standards. The report also urges Congress to look at imposing a fuel tax in order to induce truck users to optimize the fuel efficiency of their operations.