The US Environmental Protection Agency (EPA) has proposed rolling back emissions standards for new heavy-duty trucks and buses, cutting the warranty period for emissions-control components from ten years to five and delaying when the current useful-life rules take effect. At a press event, Administrator Lee Zeldin said the changes retain the underlying pollution limits while removing what he called “the single biggest cost of all to the trucking industry.”

Zeldin emphasised: “We’re proposing to roll it back while keeping the underlying emissions standards in place.” The proposal targets rules finalised under the Biden administration in 2023, which cut the federal NOx limit for heavy-duty vehicles by nearly 90% and extended their useful life from 435,000 miles or ten years to 650,000 miles or 11 years, with a warranty period stretched from 100,000 miles or five years to 450,000 miles or ten. Under the new plan, the stricter NOx threshold remains in place, but the extended warranty reverts to five years and the useful-life extension would not take effect until 2030 rather than 2027.

The EPA is also proposing to eliminate deratements entirely—that is, the practice of automatically throttling a truck’s speed to as low as 5 mph when a Diesel Exhaust Fluid or emissions sensor fails. The proposal would replace this practice with visual and audible warnings that let drivers reach a repair shop while retaining the truck’s normal power. The EPA estimated that the combined changes could save the trucking industry up to US$12bn, including as much as US$6,000 off the sticker price of a new vehicle.

Industry voices have largely proven effusive about the proposal. Cummins Chief Executive Jennifer Rumsey welcomed the warranty change specifically, calling it a “really big deal” and praising the removal of a requirement that buyers “purchase upfront an emissions warranty over the whole life of a product.” This, she believes, gives fleets more choice in how they manage compliance costs. 

The proposal also introduces nonconformance penalties allowing engines that temporarily miss the new NOx standards to keep selling. The measure is aimed at avoiding supply disruptions during the transition away from higher-polluting vehicles. 

Critics have argued the changes gut the practical enforcement of standards that remain nominally unchanged. Guillermo Ortiz, Senior Clean Vehicles Advocate at the Natural Resources Defense Council, said: “Warranty and useful life requirements sound so dry and like corporate fine print, but they’re the actual teeth of this clean air rule.” He noted that a standard becomes meaningless if the underlying technology is not required to keep working.

The EPA’s own modelling of the 2023 rule estimated it would prevent 6,700 hospital and emergency department visits and 18,000 cases of childhood asthma onset annually by 2045; the agency’s current proposal projects the rollback will raise NOx pollution from trucks by 4.2% by 2030 and 11.6% by 2055. Heavy-duty trucks make up only around 5% of vehicles on the road but disproportionately drive the nitrogen oxide emissions linked to respiratory and cardiovascular illness.

The move follows a broader pattern of Trump administration EPA rollbacks this year, including a May proposal delaying emissions standards for MY2027 light- and medium-duty vehicles and a separate effort to rescind 2024 limits on the carcinogenic gas ethylene oxide. For manufacturers, the trucking rollback may offer some genuine near-term cost relief. For climate and public health advocates, it is another glaring instance of warranty and compliance mechanics, rather than the headline emissions targets themselves, being used to soften rules without formally abandoning them.