California regulators are considering approval of far-reaching anti-smog regulations that would require automakers to ensure that 15 per cent of all vehicles sold in the State by 2025 are zero emission vehicles, while remaining cars will be required to show dramatically improved fuel efficiency.

The California Clean Air Board had been scheduled to vote on the proposal on Thursday, but were still listening to a procession of speakers. They represented the auto industry, environmental organisations and consumer groups, all voicing support for the rules that would transform that California auto scene.

California has traditionally set the standards for auto emissions across the U.S. Fourteen other States currently follow California’s emission goals and the new standards have been compiled in conjunction with federal regulators so they can form the basis of a national emissions policy.

The new regulations will begin with cars sold in 2015, and impose a gradual mandate that by 2025, one in seven vehicles sold in the State will be an electric or hydrogen zero emissions vehicle or plug-in hybrid.

Board officials estimated that the new technologies needed to reach this goal would add between 1,400 dollars and 1,900 dollars to the price of a new vehicle, but would save more than three times that much in reduced fuel costs.

The regulations also set a goal that by 2050, 87 per cent of all California vehicles will be zero emission hydrogen or battery vehicles, with most of the remainder made up of hybrid vehicles. What the board called Advanced Gasoline Vehicles will by that time make up less than 10 per cent of all the vehicles in the largest State in the US.

“We can’t afford to wait. We have to act on these issues now,” said Mary Nichols, chairman of the California Air Resources Board, who called the proposal “historic” and said it would “lead the nation and the world.”