Skip to main content

The California Air Resources Board has released a summary of recent changes to the transportation refrigeration unit rulemaking, with additional information on key elements staff may include in amendments to the TRU Airborne Toxic Control Measure. These amendments may affect both truck and trailer TRUs and TRU generator set engines.

CARB is expected to consider the proposed amendments in fall 2021. The amendments may include the transition of diesel truck TRUs to zero-emission, a more stringent diesel particulate matter emission standard for newly manufactured TRUs in other categories, as well as lower global warming potential refrigerant and facility reporting requirements. CARB staff plan to assess zero-emission options for trailer TRUs and the remaining TRU categories in a second rulemaking for CARB consideration in the 2023-2024 timeframe.

Below are key elements staff may include in the 2021 amendments:


  • Newly manufactured truck TRUs, trailer TRUs, domestic shipping container TRUs, and railcar TRUs shall use refrigerant with a global warming potential less than or equal to 2,200.
  • Model year 2023 and newer trailer TRU, DSC TRU, railcar TRU, and TRU generator set engines shall meet the Ultra-Low-Emission TRU performance standard.


  • TRU OEMs shall not manufacture a trailer TRU, DSC TRU, railcar TRU, or TRU generator set unless it is equipped with an engine that meets ULETRU.


  • Applicable facility owners shall register the facility with CARB, pay fees every three years, and report all TRUs that operate at their facility to CARB quarterly or attest that only compliant TRUs operate at their facility.
  • TRU owners shall register TRU (including out-of-state based) with CARB, pay fees (every three years), and affix CARB compliance label (every three years).
  • Truck TRU fleets shall transition to zero-emission at 15 percent each year (for 7 years). All truck TRUs operating in California shall be zero-emission by December 31, 2029 (compliance extension may be granted due to infrastructure delays).

Note that these are potential amendments only, to be confirmed later this year. There is no formal comment period for the changes, but CARB is accepting questions or comments. Visit New Transport Refrigeration Unit Regulation in Development on CARB’s website for details.

Feature Image
Newsletter Issue
feature on advocacy and policy
Featured post
Publish on homepage
Feature on "Incase You Missed It" Section of The Bulletin