Executive Summary

Aerodynamic bumpers are contoured to better match the shape of the underside of the hood and fender area. They curve under to replace flatter bumpers, which act as snowplows to the air. 

Where OEMs diverge on aerodynamic bumper design is with air dams under the bumpers. OEMs have investigated a variety of options to optimize this area. The air dam tends to decrease the front clearance to the ground. This reduction in ground clearance causes the aerodynamic stagnation point to move. The location of the stagnation point affects the share of air that is routed under the vehicle, to the sides of the vehicle, into the grille, or over the top of the vehicle.

Tractor Aerodynamics
What Fleets Are Saying

“We continue to update our fleet with more fuel efficient post-2014 U.S. Environmental Protection Agency emission compliant engines, install aerodynamic devices on our tractors, and equip our trailers with trailer blades, which all lead to meaningful improvement in fuel efficiency.” — Knight Transportation

“Appearance and detail of our equipment means a lot to our drivers. Drive wheel fairings don’t just save us money, but our drivers like them too.” — Brad Pinchuk, Hirschbach

“Sleeper tractor aerodynamics have been finely tuned by all OEMs. Eliminating various features can add 10% to a fleet’s fuel expense,” — Chief engineer at a major truck builder.

 

Decision Making Tools

The Confidence Matrix has been issued to help fleets make decisions about tractor aerodynamic devices.

Decision-Making Tools

Conclusions
  • Fleets should use the standard, optimized aerodynamic packages developed by tractor manufacturers. 
  • Fuel efficiency can be lowered by about 10% by moving to partial or no aerodynamics.
  • Tractor and trailer ride heights should be matched for as many miles driven as possible.
  • Fleets operating day-cab tractors should pursue greater adoption of tractor aerodynamics.
  • Tractor manufacturers should design and make available aerodynamic features for day-cab tractors including those powered by natural gas.
  • Future EPA and NHTSA Greenhouse Gas Regulations will continue to challenge tractor builders to improve the aerodynamic drag of these vehicles.
Manufacturers
  • Daimler Trucks North America
  • International
  • Kenworth Truck Co.
  • Mack Trucks
  • Peterbilt Motors
  • Volvo Trucks North America