California Air Resources Board

In 2006, California adopted Assembly Bill 32, requiring California to reduce Greenhouse Gas (GHG) emissions from all sectors including mobile sources. One of the earliest actions under Assembly Bill 32 was the California Air Resources Board (CARB) adoption of the Tractor-Trailer GHG (TTGHG) regulation in December of 2008. The TTGHG regulation requires the reduction of GHG from heavy-duty tractors that pull 53-foot or longer box-type trailers on California highways by requiring the use of tires and aerodynamic equipment to improve fuel-efficiency beginning in 2010.

From CARB advisory #295 dated 12/03/2019's

"On September 27, 2018, CARB approved for adoption the California Phase 2 GHG regulation.  That regulation largely aligns California's GHG emission standards and test procedures with the federal Phase 2 GHG emission standards and test procedures, and..., provides nationwide consistency for engine and vehicle manufacturers.  The California Phase 2 GHG regulation establishes requirements for 2020 and later model year new trailers sold in California that are largely identical to harmonize the federal GHG emission standards for trailers.  California Code of Regulations (Cal. Code Regs., title 17, § 95663(c) and (d)". CARB’s TTGHG amendments also allow trailer fleet owners to comply with the TTGHG trailer requirements by using the Phase 2 GHG’s trailer certification technology prior to 2022.  This is done through a program called the Trailer Aero Device Approval Program for 2020 through 2022.

"CARB will continue to administer the California GHG trailer regulation on a voluntary basis, including processing and approving applications to certify 2020 and subsequent model year trailers, which will assist both trailer and equipment manufacturers seeking to comply with the trailer requirements in future model years and entities seeking to purchase new 2020 and subsequent model year 2020 and 2021 trailers manufactured before January 1, 2022."ⁱ

The Trailer Aero Device Approval Program allows aerodynamic device manufacturers to obtain a preliminary approval for the measured performance of aerodynamic drag reduction technologies, or combinations of technologies, in accordance with the provisions of 40 Code of Federal Regulations (CFR) § 1037.211.  Under the Trailer Aero Device Approval Program, aerodynamic device manufacturers can use three primary verification test methods (as outlined in 40 CFR § 1037.526) to determine if the aerodynamic device meets the requirements in the TTGHG regulation. The possible test methods described in 40 CFR § 1037.526 are Computational Fluid Dynamics, Coast down, and Wind-tunnel. 

CARB staff will review the submitted test results and supporting documents on aerodynamic drag reduction technologies and determine whether the technologies meet the applicable requirements. CARB will issue a written approval for such devices that demonstrate TTGHG compliance. The aerodynamic drag reduction technology will then be identified as an approved aerodynamic technology on CARB’s website and will be eligible for use in complying with the TTGHG regulation.

If you are interested in obtaining the aerodynamic device application, please send an email to ttghg.interim-AeroApproval@arb.ca.gov with the subject "ADRT Application Request".

For more information on the changes that have occurred regarding this regulation review advisory #295