California withdraws diesel truck ban and other clean-air rules ahead of Trump taking office

California has decided to abandon its groundbreaking regulations phasing out diesel trucks and requiring cleaner locomotives because the incoming Trump administration is unlikely to allow the state to implement them.

State officials have long considered the rules essential to cleaning up California’s severe air pollution and combating climate change.

The withdrawal comes after the Biden administration recently approved the California Air Resources Board’s mandate phasing out new gas-powered cars, but had not yet approved waivers for four other emissions standards for diesel vehicles that the state adopted.

President-elect Donald J. Trump has threatened to revoke or challenge all zero-emission vehicle rules and California’s other clean-air standards. By withdrawing its requests for U.S. Environmental Protection Agency approval, the Newsom administration is signaling a dramatic step back as the state recalibrates in anticipation of the new Trump era.

“California has withdrawn its pending waiver and authorization requests that U.S. EPA has not yet acted on,” Air Resources Board Chair Liane Randolph said in a statement. “While we are disappointed that U.S. EPA was unable to act on all the requests in time, the withdrawal is an important step given the uncertainty presented by the incoming administration that previously attacked California’s programs to protect public health and the climate and has said will continue to oppose those programs.”

Environmentalists were distressed, saying it puts communities at risk and dismantles key programs.

“To meet basic standards for healthy air, California has to shift to zero-emissions trucks and trains in the coming years. Diesel is one of the most dangerous kinds of air pollution for human health, and California’s diesel problem is big enough to cast its own shadow,” Paul Cort, director of the group Earthjustice’s Right To Zero campaign, said in a statement. “We’ll be working tirelessly in the coming years — and calling on Gov. [Gavin] Newsom, state legislators, and our air quality regulators to join us — to clean up our freight system and fix the mess EPA’s inaction has created.”

California’s Advanced Clean Fleet rule, which would have phased out diesel trucks, was one of the most far-reaching and controversial rules that California has enacted in recent years to reduce air pollution and greenhouse gases. It would have ended the sale of new fossil-fuel trucks in 2036 and required large trucking companies to convert their medium and heavy-duty fleets to electric or hydrogen models by 2042.

The truck fleet rule was approved in 2022 after years of analysis, public hearings and discussions with industries and experts. It would have ended diesel’s stronghold on goods movement in the state, with potentially profound effects on the state’s environment and economy. Trucking companies had already sued the state to stop the rule, saying electric and hydrogen big rigs are not practical for many uses and that it would destroy the state’s economy.

Diesel exhaust has been linked to cancer and contains fine particles that can trigger asthma and heart attacks as well as gases that form smog. Low-income, disadvantaged communities of color near ports, freeways and warehouses have long complained about noxious and dangerous diesel exhaust.

In addition, the state withdrew three other measures, including ones regulating emissions from diesel-powered locomotives, commercial harbor craft and refrigeration unit engines that are hauled by trucks and rail cars.

Under the locomotive rule, only locomotives less than 23 years old would have been allowed in California, unless they were zero emissions. The rule also limited how long they could idle. People living in communities with trains and rail yards have long complained that the emissions are making them sick.

Under the Clean Air Act, Congress more than a half-century ago granted California the unique ability to set its own standards regulating vehicle emissions because of its severe smog. But the federal EPA must grant California a waiver to implement them.

For decades, the EPA has granted California waivers to set its own ambitious, technology-forcing standards for cars, trucks and other sources. Only one waiver was initially denied — a 2008 rule setting greenhouse gas emission standards for cars — and that decision was quickly reversed and the waiver granted.

But when Trump was last in office, his administration took aim at the state’s special status to enact stricter rules — one of the more significant environmental clashes of the first Trump era. The Biden administration reversed those efforts.

California air-quality officials have been waiting for years for the Biden administration’s EPA to approve the last four rules, hoping that time wouldn’t run out. But the EPA failed to act in time.

The air board may have to rely instead on voluntary agreements with engine manufacturers, trucking companies and railroads.

“The California Air Resources Board is assessing its option to continue its progress as part of its commitment to move forward the important work of improving the state’s air quality and reducing harmful pollutants that contribute to poor health outcomes and worsen climate change,” Randolph said.

“It’s clear that the public health, air quality, and climate challenges that California faces require urgent action. We are ready and committed to continuing the important work of building a clean air future.”