Heavy-Duty Vocational Vehicles GHG Program

This page last reviewed April 27, 2017


Phase 2 Truck imageIn 2015, California Air Resources Board (CARB) contracted with U.S. Department of Energy's National Renewable Energy Laboratory (NREL) to perform coastdown and on-road testing on class 4 and class 6 box-typed trucks with and without aerodynamic devices to quantify potential fuel savings and emission benefits from using aerodynamic devices on vocational vehicles.  The study showed potential significant fuel economy and emissions benefit from the use of aerodynamic devices. In general, aerodynamic devices will yield fuel savings and emissions benefit at high speed. In the final federal Phase 2 greenhouse gas (GHG) regulation for medium- and heavy-duty vehicles, the U.S. Environmental Protection Agency and the National Highway Traffic Safety Administration allow optional emission credits for installing aerodynamic devices on regional vocational vehicles, depending on eligibility criteria. 

In 2008, CARB adopted the Tractor-Trailer GHG regulation that requires the use of aerodynamic devices and low-rolling resistance tires on heavy-duty tractors hauling 53-foot or longer box-typed trailers to reduce GHG emissions from these tractor-trailers. CARB staff is considering future measures to encourage/require the use of aerodynamic devices and/or more aerodynamic vehicle design for vocational vehicles (class 4-6) that spend a significant amount of time at high speed.  

CARB is gathering information on vocational vehicle activity and operations.  Please contact us if your fleet would be willing to participate in a survey.

What's New

Posted April 27, 2017:
CARB staff has posted the Aerodynamic Credit Concept presentation that was discussed at the April 25th, 2017 Advanced Clean Local Truck Workshop. Please see web link, Advanced Clean Trucks, for more details.
Posted November 2, 2016:
NREL's final report, "Aerodynamic Drag Reduction Technologies Testing of Heavy-Duty Vocational Vehicles and a Dry Van Trailer" is now available.  The report showed expected benefits of several common types of aerodynamic devices on selected vocational vehicles and a trailer. Results were then used to predict expected fuel savings over real-world vocational drive cycles. In addition, NREL studied how the deterioration of diesel particle filters can affect opacity and particulate matter emissions from heavy-duty vehicles. 

Posted November 1, 2016:
CARB invites you to participate in a public workshop in Sacramento on November 1, 2016, to discuss the potential to reduce GHG emissions from vocational vehicles via aerodynamic improvements and future studies and will request assistance gathering data regarding vocational truck fleets.


Date/Time Description Documents
April 25, 2017/
10:00 a.m.
Advanced Clean Local Trucks Regulatory Concept and Optional Vocational Aerodynamic Credit Concept Public Workshop Notice
Nov. 1, 2016/
10:00 a.m.
Advanced Clean Truck Strategies, Truck Aerodynamics, and Sustainable Freight Data Collection Public Workshop  Notice

Related Links


For more information, please contact:

Inder Atwal, Air Pollution Specialist, via email Inder.Atwal@arb.ca.gov or at (916) 445-0281.