Fairfax County may be crawling with buses on weekdays but some residents would like to see more of them on the weekends.

"There's a lot more to public transportation than commuting into the District," said Mary Sue Lyons, who advocates Saturday bus service within the county. "With one car, we're canned in here on weekends. We want to show the supervisors that there are other transportation needs besides commuters in this county."

Lyons and other Fairfax residents have gathered more than 500 signatures on a petition asking the county Board of Supervisors to add Saturday service on Metrobus Route 26A, which runs from West Park down Gallows and Backlick roads to Springfield Mall.

In asking for the weekend service, the residents noted that 26A is a cross-county route and is used by travelers who have business or errands within the county, not just by commuters. Gloria Hwang, another resident lobbying for the expanded service, said the route connects residential areas with shopping centers, parks, schools and local recreation centers.

"Fairfax, despite all the press, is not totally upper crust," she said. "There are all kinds of needs that we should address."

However attractive Saturday service for 26A may be to residents, it would be a major financial burden to the county, said Shiva K. Pant, director of transportation.

To initiate Saturday service, he said, Fairfax would have to request that Metro start it up. Since the bus line runs completely within county lines, Fairfax would bear the full brunt of the subsidy that area communities pay to Metro for bus service.

This summer, the county supervisors asked the county Office of Transportation to study the proposal. Last week, Pant said he doubted that his office would recommend adding Saturday service when it reports back to the supervisors next Monday.

"It is pretty hard to recommend this," Pant said. "I don't know how much that subsidy would be; we haven't pulled our figures together. But it would be substantial."

Fairfax contributed $20 million last year to Metro for bus service.

Pant said 26A is one of the least productive routes in the county. Although most routes recoup 35 percent of their costs at the fare box, he said, 26A earns only about 11 percent of its keep.

Lyons said she thinks the 26A route is underused because many Fairfax residents don't know about it and because the buses only run every hour.