City Council members pushing for a near total car ban in New York's two largest parks averted a legislative showdown with the mayor Tuesday, deciding to give his less-restrictive trial program a chance to play out.

The mayor's program, which was launched Monday and will run for six months, bans cars in Central and Prospect parks except during the morning and evening rush hours. It also allows cross-town traffic to continue through Central Park.

Council members were pushing for an almost complete ban, but withdrew a bill Tuesday that would have challenged the mayor's approach.

The central concerns, both parties say, is finding the right balance between protecting the city's parks and preventing excess traffic from clogging nearby streets.

"All the parties have decided to let the mayor's plan run its course," said Chad Marlow, a lawyer working with Transportation Alternatives, which supports the council bill. "We expect the data will demonstrate that closures to park roads does not result in a dramatic increase of traffic around the park."

The first restrictions on car traffic in Central Park were introduced in the 1960s. Some entrances to Central Park were closed to cars altogether in 2004. The recent City Council legislation was introduced in an effort to beef up the restrictions. It would have closed all of Central Park to cars, not including the cross-town transverses. Prospect Park would have been open only during the morning rush hour.

"After we introduced the legislation the mayor decided to act," said City Councilman John Liu (D-Flushing). "He didn't go 100 percent of the way, but he went 95 percent of the way."

Advocates for car-free parks are hoping the trial program will be successful enough for the mayor to permanently ban cars from park roads.

"The goal is to have car-free parks," said Paul Steely White, executive director of Transportation Alternatives. "We submitted a petition with 102,000 signers saying they want a car-free Central Park at all times. We see this summer closure as a watershed event that will test the viability of longer closures."

Bloomberg declined an outright ban on cars after some neighborhood residents said their streets would become a gridlocked mess during rush hours if all the usual park traffic was diverted.

A Parks Department spokesperson declined to comment on whether the car restrictions would be made permanent, saying it would depend on traffic-impact studies conducted during the six-month trial.

Exact street closing times are available at www.centralparknyc.org and www.prospectpark.org.