Angered by commuters speeding through their secluded community, residents of the Rustfield subdivision in Fairfax City are installing a remote-controlled iron gate at its western entrance to prohibit further trespassing inside the affluent development.

According to city and Fairfax County officials, Rustfield will be the only planned residential development in the area using such a remote-controlled protective gate. Some private residential and condominium communities post guards or use mechanical wooden arms outside their entrances. The community is located on 12 acres between Chain Bridge Road (Rte. 123) and Little River Turnpike (Rte. 236), Fairfax City's two main thoroughfares, and its private roads are frequently used as a shortcut through the traffic-plagued city.

Residents of Rustfield will be able to activate the gates from inside their cars with devices provided by the Rustfield Homeowners Association and a small, manually controlled walk-through gate will accommodate pedestrians.

Homeowners said that since the one-lane bridge over Tusico Creek, which runs through the subdivision, was completed last year, commuters and trucks use Rust Hill Place, its main road, to bypass the usual city traffic.

"It's become a public thoroughfare in here," said William Fuchs, president of the Rustfield Homeowners Association. "We're a private community with private roads that are privately maintained. We know who lives here and who doesn't."

Rustfield's 41 three- and four-bedroom, two-story town houses sell for about $250,000. Residents there pay $95 a month to the homeowner association, which is responsible for maintaining the neighborhood's three narrow streets, landscaping, painting the houses and posting signs for the private community and its 15 mph speed limit.

Resident Barnes Fitzgerald, whose ironworks company will build and install the ornamental gate for between $7,000 and $8,000, lives near Rustfield's western entrance and said vandals have torn down the speed limit sign three times in the last year and a half.

"I've seen people come through here going about 50 mph," Fitzgerald said. "And during the rush hours you can't even back out of your driveway."

Residents also complained of youngsters shouting obscenities from their cars while driving through the private neighborhood. One town house had its telephone line severed and another had a garden hose cut in half, residents said.

"It's mainly teen-agers doing these things," said Fitzgerald's wife, Pat. "Now I don't know how people will react once the gates are up. They'll probably be angry. It really doesn't make much sense to me."

The wrought iron gates, which were approved recently by the Fairfax City Council, will be almost five feet tall and will connect to existing brick columns at Rustfield's western entrance, which intersects Railroad Avenue, Oliver Street and Tusico Place.

According to plans submitted to Fairfax City's planning director by the Rustfield Homeowners' Association, only one side of the gate will open and close electrically by a remote-control device similar to those used to activate automatic garage doors.

Fuchs said residents will be given two opening devices per household. The city's police and fire departments also will be provided with the devices. A small walk-through gate will accommodate pedestrians; other guests will have to drive in through Rustfield's only other entrance, located on Chain Bridge Road.

Residents decided to put the gate at Rustfield's western entrance because the city's trash collectors use the Chain Bridge Road entry and residents did not want the gate to interfere with this service or other traffic along the busy road.

Final design plans must be approved by the city's Board of Architectural Review before construction starts in a few months.

Fairfax City Police Chief Loyd W. Smith said Rustfield is not a high crime area, and that police patrol cars occasionally drive through the development "to let them know we're alive . . . . As long as they give us an opener, I don't care what kind of gate they have."

Smith said he asked for 13 remote control devices: one for each patrol car and one for the department's dispatch unit. The fire department will keep five devices: One for its ambulance, one for the medic unit and three for each of the fire trucks.

City Mayor George T. Snyder said the Rustfield residents had every right to protect their privacy and keep commuters out.

"Those are private roadways there," Snyder said, "and the people who live there have to maintain them, plow them and repair them. They are not city streets."