A large group of Fairfax County residents, concerned about the traffic and congestion generated by the nearby Fair Oaks Shopping Center and the growing commercial district surrounding it, have decided to sell their $250,000 homes to two developers who are planning a large-scale residential development near the mall.

Owners of 86 of the 98 homes in the 320-acre Fairfax Farms subdivision already have agreed to sell their homes to the Georgelas & Sons development firm of McLean and the Hadid Investment Group of Rosslyn. The other 12 still are considering whether to sell, according to a spokesman for the homeowners group.

Georgelas said the property "is under contract," but that the price for the land will not be set until studies, financed by the developers, determine how the land should be redeveloped. The agreement calls for a three-month study period "to permit us to arrive at a fair value for the property which will reflect the best use of the land," he said.

Washington-area residents who feel they are being overwhelmed by nearby commercial development are increasingly banding together to sell their property to developers who construct still more office buildings and retail stores.

But the pending Fairfax Farms sale is unusual because the developers say that they are likely to bulldoze Fairfax Farms and erect town-house complexes, possibly along with a neighborhood shopping area to serve the residents. The land today is dominated by large rambler-style homes on wooded lots, some of which are as large as 10 acres.

However, many of the residents said that with the coming of Fair Oaks and still more massive development planned, they no longer find their homes to be the idyllic retreats they once were. Traffic, noise and pollution brought on by the increasing commercialization of the area have dramatically changed the character of Fairfax Farms, according to members of a steering committee pushing for consolidation of the lots so they can be sold.

When Edward Davis, a member of the committee, and his family moved to their home on Valley Road 10 years ago, he said there was little hint of future dramatic changes.

Today, some of Fairfax County's biggest commercial projects are either under construction or approved for construction near Fairfax Farms. Traffic in and out of Fair Oaks mall has made it unsafe for residents to use Fairfax Farms Road, the major access to the neighborhood, according to Shirley Sweeney, a 10-year resident.

Sweeney has for several years led a fight to get state and county officials to install traffic signals and reduce the speed limit along Rte. 50. She said driving no longer is safe. "I have written letter after letter, but everything falls on deaf ears," Sweeney said.

"We sit at the mouth of an exit ramp off a major interstate (Interstate 66) near the major intersection of Rte. 50 and West Ox Road between two flyover ramps leading to Fair Oaks Mall," Sweeney said.

Money, Sweeney said, is not the force driving residents of Fairfax to sell. The issues are life style and traffic.

According to Davis, many residents are senior citizens who have not coped very well with the changes in the traffic patterns and life style that the mall has brought to the community.

Residents have known that commercial development was coming since Fairfax County several years ago adopted an overall development plan known as the 50-66 study.

"But we were still happy to be out in the country," Sweeney said, until Fairfax officials a year ago approved construction of 1,800 town houses surrounding the Penderbrook golf course that abuts the western edge of Fairfax Farms. That decision prompted neighbors to organize to sell and eventually ask the Rand Realty brokers to help them find a builder or developer who would be willing to tackle a project plagued by an already bad traffic situation.

Even though the deal with Georgelas and Hadid, signed recently, contains a study period, developers and residents said they are confident that eventually it will be finalized. Because of Fairfax County's land-use policy, which calls for maintaining low-density residential development on the site, developers and residents have abandoned the idea of creating another giant commercial center there.

Georgelas said the 14 million square feet in the area should be plenty to accommodate what Fairfax County calls a planned development housing project. He said the developers would like to build six to eight town houses per acre on the land but aren't yet sure of the final shape of the project because of environmental problems on the site. Fairfax Farms is divided by an environmental quality corridor known as Difficult Run.

Under the planned development housing zoning category, developers also might be permitted to build a neighborhood shopping center.

Before any change can happen, the developers said they would have to devise a transportation network that serves not only the site, but also helps relieve existing traffic problems. "We need a very creative network," Georgelas said.

A committee of residents, headed by Sweeney and Davis, recently asked Fairfax officials to change its land-use plan to allow for a mix of commercial and residential development on the land as part of the 1986 review of the county's comprehensive land-use plan.

The deal with Georgelas and Hadid is not tied to whatever decision might be made by county officials this year, developers said.