The Truck and Engine Manufacturers Association has sued the California Air Resources Board, saying the agency has not provided enough lead time for truck and engine makers to meet its latest emission standards due to go into effect in 2024.
EMA Lawsuit: CARB Emissions Rule Violates Clean Air Act
The Truck and Engine Manufacturers Association said the California Air Resources Board's new emissions regulations don't give manufacturers enough time to comply.

More than half of the commercial vehicles on the road in the U.S. are advanced clean-diesel technology models, according to the Diesel Technology Forum.
Photo: Diesel Technology Forum
On Dec. 22, 2021, CARB adopted the Heavy-Duty Engine and Vehicle Omnibus Regulation, 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 Omnibus Regulation requires heavy-duty engine and vehicle manufacturers to comply with the new standards on Jan. 1, 2024, giving manufacturers only two years of lead time.
The federal Clean Air Act allows California to establish its own emissions standards, EMA said, provided California meets certain requirements — including providing heavy-duty on-highway engine and vehicle manufacturers four full model years of lead time.
In its filing, EMA said the Omnibus Regulations would require, among other things, that heavy-duty engine manufacturers:
Develop and deploy new technology to reduce nitrogen oxide (NOx) emissions initially by 75% and particulate emissions by 50%.
Demonstrate emissions compliance on entirely new test cycles.
Ensure emissions compliance for certain “Class 3” heavy-duty engines using new durability test procedures out to an extended “useful life” range of 150,000 miles instead of 120,000 miles.
It would require engine manufacturers to redesign, test and build their engines to comply with all of those new requirements starting with Model Year 2024, which begins, at the latest, on Jan. 1, 2024.
“Truck and engine manufacturers are proud that today’s modern engines reduce harmful emissions to near zero levels, and we are committed to building still cleaner products,” said EMA President Jed Mandel in a news release.
“But CARB must provide manufacturers the minimum four years of lead time mandated by Congress…. This lawsuit is simply to ensure that CARB follows all of the prescribed rules — one of which is intended to maximize the likelihood of the smooth and successful implementation of new emission standards.”
Environmental Groups: ‘A New Low’
Environmental groups were quick to criticize the suit. They claim that truck and engine makers that are part of EMA are being hypocrites, as several prominent executives have publicly called for faster action to meet global emissions targets.
A blog post on the website of the Natural Resources Defense Council characterized the action in a headline, “Truck Manufacturers Sue to Continue Polluting,” accompanied by a photo of an old rig belching black smoke in 2014.
“EMA’s lawsuit is a direct attack on our communities, lungs, and the environment,” wrote Patricio Portillo, senior advocate for NRDC’s Climate & Clean Energy Program. “It’s also a new low for EMA, a trade association comprised of vehicle and engine manufacturers who have made public statements about their desire to clean up vehicle pollution….
"This lawsuit is evidence that no matter the public statements, truck manufacturers will never clean up their act unless forced to by vehicle emission standards.”
In an email, a spokesperson representing a group environmental organizations, including NRDC, said, “These standards will literally save lives. American Lung Association's latest State of the Air report finds that California cities continue to top the country's list of most polluted. Diesel death zones situated arounds ports and warehouses are some of the clearest examples of environmental racism in the state thanks to decades of redlining. These communities are desperate for relief.
“Adding insult to injury, California gives EMA members — e.g. Volvo, Daimler, Cummins — hundreds of millions of dollars to support clean truck R&D.”
Other groups represented by this email in addition to NRDC include the Center for Community Action and Environmental Justice, the People's Collective for Environmental Justice, East Yard Communities for Environmental Justice, Central California Asthma Collaborative, BlueGreen Alliance, and Earthjustice’s Right to Zero campaign.
For more on diesel emissions:
More Equipment

Top Green Fleets of 2026: Nomination Deadline Extended
Is your company a leader in sustainability efforts among trucking fleets? If so, Heavy Duty Trucking's editors want to hear from you.
Read More →
Kenworth Announces Reinforced Front Frame Option for T880 and T880S Models
Kenworth has released a factory-installed reinforced front frame option for T880 models, designed to simplify upfits, cut costs, and speed time to service.
Read More →
Stoughton Rolls Out PureBlue Reefer Trailer, Raises Safety Bar With 40-mph Rear Impact Guard
Stoughton’s new refrigerated trailer platform delivers double-digit efficiency gains while a next-generation rear impact guard exceeds current crash standards.
Read More →New Lightweight Wheel Cover Targets Simpler Aero Gains [Watch]
Watch to learn how Deflecktor's new wheel cover design is taking a simpler approach to aerodynamics, with an eye toward making it more practical for both trucks and trailers.
Read More →
How Maxiloda’s Glide System Unlocks Hidden Trailer Capacity
By turning unused vertical space into usable capacity, Maxiloda’s Glide system helps fleets move more freight per trip while reducing loading risks and equipment damage.
Read More →
Deflecktor: Hubbub Aerodynamic Wheel Cover Cost-Effective Even for Trailers
Aerodynamic wheel covers can deliver small but meaningful fuel-economy gains for fleets, and Deflecktor says its latest design aims to make the technology easier and more affordable to deploy.
Read More →
Kenworth Revives Iconic 'TourAmerica' Paint Scheme
Kenworth’s new, limited-edition scheme celebrates trucking heritage while supporting a nationwide mobile museum tour.
Read More →
Ryder Joins International’s Autonomous Truck Pilot on Texas Freight Lane
Ryder and International take autonomous trucking out of the lab and onto a live, 600-mile Texas freight lane.
Read More →
FTR: Class 8 Orders Stay Hot in March Despite Monthly Dip
Fuel prices aside, Class 8 demand remains elevated as freight fundamentals improve and fleets regain confidence in long-term investments.
Read More →
Fontaine Expands Flatbed Lineup with New Fleet-Focused Models, Eyes 2027 Launch
Fontaine is broadening its flatbed lineup with new models aimed at fleets, including a lightweight aluminum trailer expected in 2027 that emphasizes durability, repairability, and lower cost.
Read More →
