Nearly 1 billion gallons (3.8 billion L) of diesel fuel could be saved annually if the throngs of heavy-duty trucks and trailers on U.S. highways adopted some of the aerodynamic advancements pioneered on passenger cars, a new study says.

The findings come as part of a 2-year collaborative effort between the U.S. Department of Energy and four members of the Truck Manufacturers Assn. (TMA): International Truck and Engine Corp., Freightliner LLC, Mack Trucks Inc. and Volvo Trucks North America.

Together, the four companies comprise about 75% of the Class 8 truck market in the U.S., says the TMA, a nonprofit technical trade group based in Washington.

Specifically, results from the study, which was funded by the DOE’s FreedomCAR and Vehicle Technologies Office through the National Energy Technology Laboratory, focused on four areas of improvement for tractor-trailer design:

  • Gap enclosure – Reduces aerodynamic drag and disturbance from the gap between the tractor and trailer.
  • Side skirts for trailers – Improves aerodynamics and reduces airflow beneath the trailer in crosswinds.
  • Boat-tail trailers – Tapered tail design minimizes disturbances in the trailer’s aerodynamic wake.
  • Improved side-mirror design – Reconfigured shape supports systems to direct air around the trailer and reduce drag.

Combining all these improvements on one vehicle could result in a reduction in aerodynamic drag of up to 23%, the TMA says, noting every 2% reduction in drag accounts for a 1% improvement in fuel efficiency.

“To put this into perspective,” says TMA President Robert Clarke, “if every tractor/van/semi-trailer/combination truck in operation in the U.S. adopted these technologies and improved fuel efficiency by 10%, it would translate into nearly 1 billion gallons per year of fuel savings.”