A small but controversial new section of bicycle trail along the George Washington Memorial Parkway was completed this week after a delay of more than four years and an expenditure of $467,000 in federal funds.

And it has a new full-time bicycle ranger to patrol it.

The two-mile section just north of Fort Hunt, paved earlier this week, is located aong the west side of the parkway on National Park Service land. Bicyclists had been routed over small Fairfax County roads since the popular bike trail between Washington and Mount Vernon was constructed in 1973.

Residents west of the parkway, who wanted the Park Service to route the bike trail along the east side where the rest of the trail is located, had sued the park Service and blocked the construction of the trail until this summer. The Park Service made detailed studies of varying routes and concluded that the new west-side path would be safer and do less scenic damage to the parkway.

Congress had appropriated $524,000 for the new two-mile section of trail, more than the entire trail cost in 1973. The funds were to cover a bicycle bridge over the parkway, if necessary. A large portion of the funds were used for studies and an environmental review, because of the concern over the trail's location. The two-mile stretch above Fort hunt is the only part of the 14-mile trail, outside the city of Alexandria, to be routed along public streets.

The trail's new bike ranger, Carotine DuBois, patrols the path with a bag full of "band aids, bike tools and bird books," she says, ready to assist the 200,000 bicyclists a year who pedal along it. Additional thousands of joggers, walkers, bird watchers, skateboarders and even an occasional wheelchair use the trail. The trail passes through Dyke Marsh, a bird sancturay.

DuBois, assistant bicycle coordinator for the District of Columbia transportation department until this summer, helped organize Bikecentennial during 1976, the nonprofit group that routed more than 4,000 bicycists along back roads across the country from Yorktown to the West Coast.

She wears a bike helmet, carrying her ranger hat on a rack, but pedals her own 10-speed bike on the job. A U.S. Park Police officer previously had been assigned to patrol the bike trail, on a government-issue bike, but only on some weekends and during periods of heavy use.