California officials voted Friday to fully transition the state’s public bus fleet to electric power by 2040.

The California Air and Resource Board (CARB) voted unanimously to make California the first state with such a commitment.

The new rule will ultimately require the production and purchase of more than 14,000 new zero-emission buses.

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The decision comes at a time when the nation is facing a crossroads on how to deal with worrisome climate reports that suggest the effects of climate change will soon be inevitable if greenhouse gas emissions are not significantly curbed in the next decade.

While the Trump administration has questioned how much the U.S. is responsible for cutting back emissions with other countries like China emiting at higher rates, California leaders have taken the lead in adopting new climate-aiding measures.

The latest move was championed by environmentalists.

“This is the biggest public transportation breakthrough since we switched from trolleys to diesel buses a century ago,” said Jimmy O’Dea, a senior vehicles analyst at the Union of Concerned Scientists, in a statement.

“Bus riders, bus drivers and anyone who has gulped the exhaust from a passing truck or bus knows we must do something about these vehicles. Electrifying them is a one-two punch: we reduce carbon emissions that worsen climate change and we clean up the air we breathe.”

“Today California took a momentous step to realizing the right to zero on our city streets,” said Adrian Martinez, attorney for Earthjustice.

“From disadvantaged community members choking on diesel and gas tailpipe fumes, to college students, to transit agencies like LA Metro, to bus riders, to doctors and nurses, to environmental advocates, Californians made it clear they demand zero-emissions buses in communities statewide.”

The state of California, which has some of the worst air pollution in the country, has long sought ways to purify its atmosphere.

Earlier this year California also voted to become the first state to mandate new homes be retrofitted with solar panels. In September, the Gov. Jerry Brown (D) signed a bill making California the first state to commit to transitioning to a 100 percent renewable energy electric grid by 2045.

Following the Trump administration’s announcement in the summer that it intends to weaken an Obama-era vehicle emissions standard, state officials said they plan to sue for their right to implement more stringent regulations.