The U.S. EPA granted a waiver for the California Air Resources Board to implement its Omnibus NOx regulation for heavy-duty vehicles. The move comes with just more than a month left in the Biden Administration’s term. 

The waiver grants California federal permission to implement its latest NOx regulation for heavy-duty vehicles. The waiver is a significant development for regulating heavy-duty vehicle and engine manufacturers. It sets record-low NOx and particulate matter emissions standards for medium- and heavy-duty engines and vehicles.

Under the Clean Air Act, California is the only U.S. state that can set its own emissions standards that exceed federal standards. California’s emissions regulator, CARB, must receive a waiver for each regulation that exceeds federal standards. The regulation began with model year 2024 equipment, but CARB could not enforce the rule until EPA granted a waiver.

CARB adopted the regulation in 2021 and made amendments to the regulation as recently as December 2023. CARB submitted its last waiver request for the regulation in July 2024.

Three major CARB regulations affect the trucking industry most today:

• Advanced Clean Trucks, which requires manufacturers to reach minimum electric vehicle sales
• Advanced Clean Fleets, which requires fleets to have a minimum portion of EV among their vehicles
• And Omnibus, which sets low NOx emissions standards for manufacturers’ equipment

With the latest EPA approval, both ACT and Omnibus have received EPA waivers. ACF still has not received a waiver.

CARB regulations affect not only California’s operations but also individual U.S. states, which can choose to adopt individual CARB regulations. Currently, nine other states have plans to adopt Omnibus.

Massachusetts and Oregon plan to enforce CARB’s NOx standards for MY 2025 equipment. New York, Vermont, and Washington plan to adopt the standards for MY 2026. Colorado, New Jersey, New Mexico, and Rhode Island plan to adopt the standards for MY 2027.

See also: Fleets explained: Emissions regulations

Trucking industry groups criticize NOx waiver

Trucking industry associations are broadly critical of emissions regulations. Two major associations quickly criticized EPA’s waiver approval and expressed hope that the incoming Trump administration would weaken environmental regulations.

“This ill-advised waiver will be short-lived,” Chris Spear, American Trucking Associations president and CEO, said. “We look forward to the incoming administration and soon-to-be EPA Administrator Lee Zeldin reversing these misguided policies and restoring common sense to the nation’s environmental policy.”

The Owner-Operator Independent Drivers Association also criticized the waiver.

“The Omnibus Low-NOx waiver for California calls into question the policymaking process under the Biden administration’s EPA. Purposefully injecting uncertainty into a $588 billion American industry is bad for our economy and makes no meaningful progress towards purported environmental goals,” Todd Spencer, OOIDA president, said. “We look forward to working with the Trump administration’s EPA in good faith towards achievable environmental outcomes.”

The incoming Republican federal government will likely weaken environmental standards and revoke CARB’s waivers. California called a special legislative session to prepare for the coming political conflict.