Can you own too many cars? In Berkeley, yes.

After a moment of hesitation, Shana Rocklin lowers her voice and confesses. Yes, she owns three cars. Yes, she parks them on the streets of her curb-abundant neighborhood. And yes, she deserves to be punished.

In many other cities in America, her automobiles wouldn't even be an afterthought. But this is not the wide-open Western plain or the freeway-blanketed landscape of southern California, where car ownership is seemingly the 11th article of the Bill of Rights. Here, in a city of causes that have ranged from the profound to the bizarre, today's target is the clutter of extra automobiles.

In what would be the first law of its kind in the United States, Berkeley is considering a tax on residents who own more than two cars.

Authorities wonder if it can be enforced. Experts question whether it can spread. But to many people here, that's beside the point. This is merely the latest spat in the ill-arranged marriage between a city determined to save the world and the machine that many here think is actively destroying it.

"In some parts of the country, cars are perceived as the epitome of freedom," says Kriss Worthington, the City Council member who made the proposal. "In Berkeley, they're seen as a necessary evil.... The general philosophy is that cars should pay for what their impact on society is."

The impact of extra cars in Berkeley is relatively small, Mr. Worthington acknowledges. Census figures suggest that only about 500 residents own three or more cars, and under his plan, these people would pay no more than $200 to register each vehicle beyond two.

The purpose, Worthington says, is to create an incentive for multiple-car owners to get rid of a few - unclogging curbs. And Ms. Rocklin says it would work, at least for her. "I would get rid of [my third car] rather than hold on in case I ever need it," she says.

But there is symbolism behind the proposal, as well. This is a city that has all but declared war on the gas-guzzling automobile.

To force cars off neighborhood side streets, it has turned its once-logical waffle-iron grid into a labyrinth of detours and cul-de-sacs with speed bumps and concrete planters. It has converted 200 buses, garbage trucks, and fire engines to run on an environmentally friendly form of diesel made from recycled cooking oil. And it has the second most extensive system of bicycle paths of any city in the US.

Worthington bicycles to City Hall, and the mayor participates in a car-share program that lets hundreds of residents drive communal cars. "Berkeley has always been at the front of alternative transportation," says Larry Magrid, executive director of City CarShare. He notes that Berkeley has the second most successful car-share program in the country - behind only San Francisco.

Some people roll their eyes at the proposal, of course. "It goes against all of what this country stands for," says a bespectacled Wayne Anderson, sitting along bustling Shattuck Avenue.

For a family with children, "you can't put [registrations] in the [kids'] names because it's even more of a penalty," he says.

Even supporters want to make sure working families who need multiple cars to get to work aren't penalized. But here, where people know how to pronounce "Kucinich" and a street-side stand implores "LaRouche vs. Cheney: Continue the American Revolution," socialist sympathies never linger far below the surface.

"It sounds fair to me," says college student Enrique Casillas, waiting for the bus. "Someone who has that luxury should have the extra money."