Association Challenges California's Clean Truck Partnership
The Western States Trucking Association is challenging a deal that truck and engine makers made with California to continue to meet the state's truck emissions rules even if it lost the federal authority to implement those rules

California's NOx and zero-emission truck regulations are dead..... but are they really?
Image: HDT Graphic
The Western States Trucking Association is challenging a deal that truck and engine makers made with California to continue to meet the state's truck emissions rules even if it lost the federal authority to implement those rules.
The association filed a petition with California’s Office of Administrative Law, alleging that the California Air Resources Board, by entering into the Clean Truck Partnership, improperly adopted what was in reality a regulation in violation of the California Administrative Procedure Act.
CARB, the Truck and Engine Manufacturers Association, and truck and engine makers entered the Clean Truck Partnership in the summer of 2023.
In that deal, the OEMs agreed to comply with CARB’s Advanced Clean Trucks and Heavy-Duty Omnibus regulations, “irrespective of the outcome of any litigation challenging the waivers or authorizations for those regulations or of CARB’s overall authority to implement those regulations.”
Truck makers did this in exchange for California's commitment to work collaboratively with manufacturers to provide lead time to meet specific regulatory requirements before imposing new ones.
Congress vs. California Air Resources Board
After Congress recently voted to revoke the Environmental Protection Agency waiver for California’s Advanced Clean Trucks regulation and the Heavy-Duty Low-NOx Omnibus rule, CARB has taken actions indicating it’s forging ahead in its truck emissions goals by expecting truck and engine makers to abide by the Clean Truck Partnership agreement.
On May 23, CARB issued a Manufacturers Advisory Correspondence document saying it will continue to certify engines and trucks pursuant to the ACT and Omnibus regulations for model year 2026 in part to “facilitate meeting the commitments of the [CTP]," according to the WSTA petition.
After President Trump signed the congressional orders revoking the EPA waivers, California Gov. Gavin Newsom issued an executive order that, among other things, continues the Clean Truck Partnership work and requires reports on progress every six months.
Western States Trucking Calls CTP 'Invalid Underground Regulation'
“The CTP creates new regulatory obligations for virtually an entire industry — including the requirement to follow regulations that are not authorized by federal law,” said the association in its petition.
“It also purports to grant CARB new powers, such as the power to require new vehicle and engine certifications to meet requirements that do not have federal authorization. Although the CTP stands in for CARB regulations, CARB did not comply with the APA in introducing this alternative regulatory regime. Thus, the CTP is an invalid underground regulation.”
The petition notes that if CARB had gone through the APA procedures, it would have had to publicly explain and justify the implementation of its stringent zero-emission vehicles policy in the face of federal preemption, and purchasers and fleet operators would have had the opportunity to comment on the issues the CTP will create.
Critics: Petition is ‘Attack on the Industry’
Critics of the Western States Trucking Association petition say the Clean Truck Partnership has helped provide certainty to businesses that have already adopted electric trucks, at a time when shifting federal regulations have caused uncertainty.
The WSTA petition undermines that certainty, critics say, calling the challenge an attack on the future of the trucking industry.
One of those critics is Craig Segall, who helped negotiate the Clean Truck Partnership Agreement as CARB deputy executive officer and assistant chief counsel.
He said the association's attack on the agreement would set the trucking industry back and called on truck manufacturers to stand by the agreement they signed two years ago.
“The companies shook hands with California on a workable path forward," Segall said in a news release.
"Will they now stand behind their commitments as others attack them? Or will they stay silent during this attack? My hope is that they will stand up for the electric future they claim to support.”
More Equipment

NHTSA Moves to Rewrite Truck Fuel-Economy Rules
The National Highway Traffic Safety Administration says it lacks authority to regulate medium- and heavy-duty truck engines separately from complete vehicles, but the existing standards have not yet been eliminated.
Read More →
Detroit Opens Orders for EPA 2027 Engines
Detroit isn’t starting from scratch to meet EPA 2027 diesel emissions standards. Its Gen 6 DD13 and DD15 engines keep much of today’s platform while updating the fuel and aftertreatment systems.
Read More →
Carrier Transicold Adds All-Electric TRU for Stationary Cold Storage
Carrier Transicold’s new Vector 8200 all-electric transport refrigeration unit gives fleets a diesel-free option for temporary refrigerated and frozen trailer storage.
Read More →A Closer Look at Kenworth’s Electric T880E Vocational Truck [Video]
Learn more about Kenworth's T880E battery-electric vocational truck at the Paccar Technical Center, including its range, applications, upfitting considerations, and PTO options, in this HDT Spotlight video.
Read More →
Kenworth T880E Brings EV Power to Vocational Trucks
A closer look at the Kenworth T880E’s range, charging, powertrain and upfit options — and where fleets are showing the most interest.
Read More →
What the U.S.-Canada Trade War Means for Trucking
Escalating U.S.-Canada tariffs could disrupt cross-border freight, reduce truck volumes, raise costs, and create new uncertainty for carriers on both sides of the border.
Read More →
Autonomous Truck Testing Moves Ahead in California as Teamsters Challenge Rules
California has begun permitting heavy-duty autonomous truck testing, with Aurora and Kodiak among the first to receive approval, as the Teamsters sue the DMV over the new regulations.
Read More →Behind the Wheel of the New Mack Anthem [Video]
HDT takes the new Mack Anthem around Mack’s Pennsylvania test track to see how its driver-focused design, technology, visibility and handling perform from behind the wheel.
Read More →
DTNA Plans New U.S. Truck Plant as Manufacturing Footprint Shifts
Daimler Truck North America is evaluating sites for a new assembly plant expected to open in 2029 while winding down operations at its longtime Portland manufacturing facility.
Read More →
Great Dane Flatbed Trailer Offers Light Weight and Strength
Freedom Ultra is designed for a wide range of open-deck applications, including building materials, lumber, machinery, steel products, industrial freight, and coil hauling.
Read More →
