The state Air Resources Board on Friday approved revolutionary tailpipe emission standards, a move expected to result in millions of electric and other alternative-fueled cars on California roads beginning in 1997.

The tough standards, approved on an 8-0 vote in Los Angeles, are expected to have dramatic implications for California motorists, automobile manufacturers and oil companies.

As early as 1998, 2% of all new cars sold in California--an estimated 40,000 vehicles--must be electric powered. By the year 2003, 200,000 cars--10% of all new cars sold--would have to be electric powered.

In addition, far greater numbers of other cars powered by cleaner burning methanol, ethanol or compressed natural gas are expected to be on the road because it is believed that those fuels are the only ones that can comply with the stringent new standards, the toughest in the world.

The new standards will slash tailpipe emissions in half beginning in 1994. Over the next five years, the standards would progressively tighten until every new car sold would be from 70% to 100% less polluting than cars produced in 1994. Cars built before 1994 would not have to meet the standards.

Backers of the plan hailed its approval and called it a major step toward finally bringing California's smoggiest urban areas into compliance with federal clean-air standards.

"I think we took a gigantic step forward today. We will have to wait and see if we put all the right pieces together," ARB Chairwoman Jananne Sharpless said after the vote.

James M. Lents, executive officer of the South Coast Air Quality Management District, added: "To me, it's just a revolutionary change from where we were three years ago to having a proposal on the table today that will get the job done."

Last-minute changes to meet objections from oil companies and automobile manufacturers appeared to ease their concerns.

"We are on board," said Samuel A. Leonard, director of automotive emission control for General Motors Corp.

While automobile and oil companies questioned how much public acceptance alternative-fueled cars would have, backers of the plan predicted a strong market because of widespread concern about the environment.

But, they stressed that alternative fuels must be competitively priced and at least equal to gasoline in performance. Executives of electrical and natural gas utilities enthusiastically endorsed the program.