California Air Resources Board

In December 2008, the Board approved the Tractor-Trailer Greenhouse Gas (TTGHG) regulation, which became effective January 1, 2010.  The regulation reduces the GHG emissions from long-haul tractors and trailers by improving the aerodynamic performance and reducing the rolling resistance of tractor-trailers.  The requirements specified in the regulation are based on elements of the U.S. Environmental Performance Agency's SmartWay program.

In 2014, concurrent with the adoption of California Phase 1 GHG regulations, CARB modified the TTGHG regulation by sunsetting the requirements for model year 2014 and later tractors.  Affected tractors under this regulation were no longer required to be SmartWay verified models or use SmartWay verified low rolling resistance (LRR) tires because such requirements were duplicative of the then newly adopted Phase 1 certification requirements for tractors. 

In 2018, concurrent with the adoption of California Phase 2 GHG regulations that introduces trailer standards, CARB modified the TTGHG regulation by providing trailer fleet owners the option of complying with the TTGHG regulation by using a California Phase 2 certified trailer, or by using a trailer retrofitted with Phase 2 compliant aerodynamic technologies and LRR tires. The modification also includes the term “Long box-type trailer” defined as a trailer that is greater than 50 feet in length.  This definition is consistent with the Phase 2 regulation language.  

For further information, please call 866-6DIESEL (866-634-3735) or email at: 8666diesel@arb.ca.gov. Financial assistance is available through the Federal Diesel Emissions Reduction National Program (DERA).