For more than a year, Chain Bridge has been a one-lane cripple, creating confusion and frustration for the many motorists who use the bridge. But D.C. transportation officials say relief is around the corner.

By mid-December, transportation officials expect a major overhaul of the bridge to be completed, the latest improvement to a crossing point that has served this area since the late 1700s.

The major purpose of the $4.97 million project, according to D.C. transportation officials, is to widen and strengthen the bridge, giving it a new, 30-year lease on life.

"You either fixed it now or you lost the bridge," D.C. Transportation Director Thomas M. Downs said.

The District began redecking and widening the three lanes on Chain Bridge in June 1981, leaving the bridge with one lane to handle commuting needs between Virginia and the District.

"I can never figure out when [traffic] is going which direction," said Mary Pederson, an Arlington resident who has given up using the bridge for now.

The schedule allows traffic from Virginia to the District from 6 a.m. until 3 p.m. on weekdays. From 3:30 p.m. until 5:30 a.m. commuters can use the bridge only from the District to Virginia, and on weekends the schedule changes again, with Virginia-to-District traffic only.

Although the District has jurisdiction over the bridge, both the District and Virginia have contributed funds to the project. The District share is $967,000, and the Virginia share is $337,000. The remainder, about $3.67 million, is from federal funds.

Even though the basic bridge structure isn't being changed -- a stone carver named Fisher will still have his signature, dated 1896, inscribed neatly on a pier -- there will be other changes.

The three bridge lanes, which were 10 feet wide each, will be replaced by a 12-foot-wide lane and two 11-foot-wide lanes. Already completed are one lane, a new bicycle ramp to replace stairs to the C&O Canal and a walkway on the upstream side for all pedestrian traffic.

But the deck is the important thing.

The redecking calls for replacing some of the steel girders and putting down corrugated metal deck forms, an advance over wooden slats that once were used as forms for poured concrete. Workers also are installing reinforced steel rods horizontally through the deck, for structural strength. The top layer of rods is coated with an epoxy to help prevent deterioration from salt used for winter road maintenance.

But the pie ce de resistance is a new, lighter-weight concrete for the bridge surface. Transportation officials say the new concrete weighs only 110 pounds per cubic foot, compared to 150 pounds for the concrete that had covered the bridge. And that is a lot of dead weight off Chain Bridge's 48,000 cubic feet.

The lighter "dead load" means Chain Bridge can carry a heavier "live load," said Raul D. Silas, a structural engineer with the D.C. Transportation Department -- and also a safer load, thanks to grooved concrete used to prevent hydroplaning in wet weather.

Despite the improvements, D.C. transportation official Horace Jones said there won't be "all that much improvement in traffic flow." The District doesn't own adequate right of way to reroute Chain Bridge, officials said, and the major concern currently is that the bridge be made safe.

In the meantime, officials said, commuters seem to have adjusted to traffic inconveniences. But in the first months of construction, transportation officials said, they got more angry calls from motorists than on any traffic project they could remember.

Although only eight traffic accidents have been reported during the project, Sgt. Randall Ramey of the D.C. police 2nd District noted, "There are lots of accidents there that we don't even know about. People are in a rush and they don't bother to report them." Ramey said one problem may be a lack of emergency phones near the bridge.

Transportation director Downs will be particularly happy when traffic returns to preconstruction status.

"Of all people, I should know better," he said recently as he described the evening he tried to go to a party in Virginia via Chain Bridge.

Downs said he got all the way to MacArthur Boulevard and Arizona Avenue: "And there it was: the traffic was going the wrong way."