The California Air Resources Board has approved amendments to toughen state standards on heavy truck smoke opacity limits as well as require motor carriers with two or more trucks to report their annual smoke test results to the agency.

The Trump administration announced that fuel-efficiency regulations for cars and light trucks are too stringent and must be revised, formally beginning a process sought by the U.S. auto industry to rollback anti-pollution targets.

As the Trump administration begins to dismantle Barack Obama’s ambitious auto efficiency regulations, California is said to be poised to retaliate by doing something that automakers have feared: de-coupling the state’s rules with those set in Washington.

The Trump administration’s chief environmental regulator signaled a coming showdown with California, warning the state won’t dictate the future of ambitious automobile fuel economy regulations enacted by the Obama administration.