For supporters of the closures -- or, as they call it, "Healthy Saturdays" -- extending the Sunday program is a logical step, a way to get residents outdoors, encourage physical activity and make the park a true respite.   "It's just kind of a no-brainer for me," said David Miles Jr., the renowned "Godfather of Skating" who can be found roller-skating most Sundays at the park. "It just draws people out to the park."

On Saturdays at the park now, Kennedy Drive is filled with cars. While motorists wait for coveted parking spaces, adults hold the hands of children, anxiously waiting for breaks in traffic to cross the street. Sundays at the park, meanwhile, have been a great time for Sunnyside resident Ed Pike to ride his bike and enjoy time with his 3-year-old daughter. The closed roads, he said, also are a place for people to learn how to bike or skate on flat land without the hassle and fear of traffic. "It's kind of obvious what the great benefit would be to have that on Saturdays as well," Pike said.

But that increased open space, opponents say, would limit weekend access to the park for people who are dependent on cars to get there, including the elderly, people with disabilities and families with children. Heather Clisby, 40, said she enjoys the closures but thinks asking for a second day is greedy.  "The city's for everyone, not just for the fit," Clisby said, as she took a break from riding her bike down Kennedy Drive on a Sunday. "You're making it exclusive."

Officials at cultural venues clustered in the park's eastern end also fear that another day of closed roads would mean another day with fewer visitors and fewer admission charges -- a trend they've already seen with the Sunday closures. The California Academy of Sciences' Golden Gate Park location has been closed since 2004 and will be until late 2008 for its rebuilding project, said marketing director Pat Kilduff. But that shouldn't be a reason to do a trial run of Saturday closures now -- or ever, she said.

The academy sees 10 percent fewer visits on Sundays than it does on Saturdays, the closed roads making the difference, Kilduff said. "Unfortunately, we're dependent on revenue," Kilduff said. She's been working with other groups to propose alternatives to the road closures, including closing different roads in other parts of the park.

The closure would come at a particularly bad time for the de Young, which reopened just six months ago with an all-night event and could reach its millionth visitor sometime in the next few weeks, spokeswoman Wendy Norris said. The existing Sunday road closure already keeps thousands of visitors away, she said. "Our mission is to educate people about art, and this would definitely make it harder for us to do that," Norris said.

The debate is practically a broken record in San Francisco, where advocates have pushed for Saturday closures for decades. Voters rejected two separate Saturday closure ballot measures in 2000, and the board scuttled a similar proposal in 2003. Supporters hope this effort will be the one to make it happen.