California passes new heavy-duty diesel regulation

September 1, 2020

The California Air Resources Board (CARB) approved on August 27 a multipronged regulation that will dramatically reduce smog-forming emissions from heavy-duty diesel trucks.

The “Heavy-Duty Low NOx Omnibus Regulation” will require manufacturers to comply with tougher emissions standards, overhaul engine testing procedures, and further extend engine warranties to ensure that emissions of NOx (oxides of nitrogen, a key component of smog) are reduced to help California meet federal air quality standards and critical public health goals.

“This regulation ensures that conventional diesel trucks will run as cleanly as possible at every point in their duty cycle,” CARB Chair Mary D. Nichols said. “It takes a significant bite out of smog-forming pollution in every region in the state.”

NOx can cause or worsen numerous respiratory and other health ailments, and is also associated with premature death.

The new standards will reduce NOx emissions by 90 percent or more when trucks are operating under “low load” real-world operations. Once it is fully phased in by 2031, the rule is expected to reduce harmful NOx emissions in California by more than 23 tons per day — the equivalent of taking 16 million light-duty cars off the road in 2031.

All components of the new rule will be phased in, allowing engine manufacturers time to prepare for compliance. The NOx standards that engines must meet will be cut to approximately 75 percent below current standards beginning in 2024, and 90 percent below current standards in 2027.