Executive Summary

These devices close the gap between the tractor and the trailer by extending the vehicle side surface into the gap while ideally not interfering with trailer swing and dip motions.

The purpose of cab and roof extenders is to restrict the airflow from entering into the trailer gap by shortening the effective tractor/trailer gap width to route air over and around the gap to the trailer.

Without extenders, air leaving the rear edge of the tractor would hit the front edge and face of the trailer causing an increase in drag

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