EMA Drops Lawsuit Challenging CARB Rule

California traffic
David Paul Morris/Bloomberg News

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The Truck and Engine Manufacturers Association has withdrawn its lawsuit alleging that California environmental regulators did not give truck manufacturers enough lead time to meet the state’s new, more rigid emission standards.

Without comment, EMA on Aug. 11 informed a federal court in California it was dropping its lawsuit against the California Air Resources Board’s adoption of a package of stringent emission standards, test procedures and other emission-related requirements applicable to new heavy-duty on-highway engines and vehicles sold in California. The laws are set to take effect for 2024 model-year vehicles.

In its legal challenge, EMA said CARB should have given manufacturers four years of lead time to prepare for the regulations taking effect. The group stressed the rules should not have been set to take effect until model year 2026. CARB formally adopted the so-called Heavy-Duty Engine and Vehicle Omnibus Regulation on Dec. 22, 2021.


The lawsuit asked a federal judge to declare the start date as invalid and unconstitutional under the Supremacy Clause of the U.S. Constitution.

“EMA filed the lawsuit to achieve clarity and prompt resolution on the lead-time issue — something all stakeholders should want,” the Chicago-based trade organization said in a statement following withdrawal of the challenge. “EMA was never challenging CARB’s independent right to regulate.”

Before the regulations can be enforced, the federal Clean Air Act requires EPA to formally grant CARB a waiver. The federal agency in July held a two-day hearing to solicit input on the regulations, which have not been well-received by many in the trucking industry. EPA has not yet announced its decision on whether it will grant the waiver, but it has granted such waivers to CARB in the past.

The EMA statement added, “At the time we filed [May 27], the U.S. Environmental Protection Agency had not yet initiated its review of CARB’s request for a waiver. We are pleased that EPA has now solicited public comment and the review process is underway.”


The new regulations drew support from state air quality officials nationwide, but EMA was joined in opposition by some trucking industry trade groups due to the lead-time issue. Specifically, the rules reduce the current heavy-truck nitrogen oxides standard from 0.20 grams per brake horsepower hour to 0.050 g/bhp-hr from model years 2024 to 2026, and to 0.020 g/bhp-hr in 2027. The regulation also lengthens the useful life and emission warranty of heavy-duty diesel engines for use in vehicles with a gross vehicle weight rating greater than 10,000 pounds.

EMA argued the highly diversified and low-volume commercial engine and vehicle manufacturing industry must design multiple new engine and exhaust aftertreatment technologies, conduct extensive testing to ensure long-term durability, integrate the new systems into extensive distinct vehicle chassis and assure customers that the new products will meet their needs through real-world demonstrations.

Glen Kedzie, vice president of energy and environmental counsel for American Trucking Associations, said EMA’s lawsuit had merit.

“Such lead time is critical to give manufacturers the ability to financially plan and undertake the necessary research and development needed to engineer solutions to meet any new standard,” Kedzie said.

When the suit was filed, CARB said it could not comment on the pending litigation, but said in a statement, “The heavy-duty Omnibus Regulation targets the largest contributor of NOx emissions (on-road heavy-duty emissions account for 31% of total NOx emissions) and is expected to provide the most NOx emission benefits to help the state reach its federal air quality standards.”

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