For repair crews on the Cabin John Bridge, life between the fast lanes is not easy.

Day and night, a relentless stream of cars and trucks speeds over the bridge, confining men, materials and equipment into a center section that is often little wider than two car lengths. A misstep could plunge a man into an 80-foot-deep channel of the Potomac so treacherous that the U.S. Coast Guard considers it unnavigable. A net of yellow nylon rope stretches ominously from deck to deck -- to prevent the worst from happening.

"It's been tight working quarters," said John Seale, a crane operator for 30 years. Each workday Seale gets up at 5 a.m. and drives 80 miles from his home in the Shenandoah mountains to go to work on the bridge. Seale says he would not give up living in the mountains just for a shorter ride.

Besides, he likes the job. Seated in the cabin of a red and white crane, Seale and his machine lasso 1 1/2-ton white Jersey barriers, hoisting them into the air like baby elephants and gently putting them into place.

For Seale, the finished bridge will be worth the wait. "You start with a hole in the ground. You see something new every day, and you look back at it and say, 'I was a part of it.' "

About 60 men work on the Cabin John bridge. The variety of skills reads like a who's who of the AFL-CIO: crane operators like Seale, pile drivers who hammer steel beams into the earth to support the bridge at either end, carpenters who build wooden forms for the concrete, and laborers who set up the barriers, break up the old bridge, lay pipes and grade the concrete.

This week the ironworkers have swung into night action. They have started setting monstrous steel girders, weighing more than 30 tons, on top of concrete piers, shaped like angular hourglasses 50 feet tall.

Yellowish-white floodlight beams are trained at the foot of the piers that ironworkers are preparing for the steel girders. Away from the glare, Montia Rice, the project manager for erecting the steel, leans against the bridge railing, taking a break with Jim Hall, the project engineer. They have joined 10 others who have been working the 9 p.m.-to-5 a.m. shift for several months.

"What it's like? Tough man, tough," Rice said. "The weather, traffic. Have you ever worked at 22 below?"

"People have no mercy," added Hall. "They throw stuff at you on Friday nights."

Hall refers to the angry motorists who get caught in one-mile traffic backups on Friday night or in the wee hours of the morning when lanes are closed for such operations as erecting the steel.

"I've been called names I never knew existed," confided the grizzled Rice. Rice, who lives in Fairfax, has helped build some of the world's largest bridges all over the country for 38 years.

There is no such thing as regular sleep when they work at night, Rice and Hall say. Both men go to their offices at Williams Enterprises at 7 or 8 o'clock in the morning to es make estimates on other jobs that require their steel.

"You sleep a little in the afternoons if you get a chance. Sleep a couple hours before you come out here. Sleep two or three hours at a time, probably three times a day," said Hall.

"You lose all relationship with days and times," Rice said.

As work progresses, the night crew members will increase so that, by midsummer, they will be doing 50 percent of all the work, says Lane Construction Corp.'s Mike Costa, who is managing the Cabin John Bridge redecking.

Otis Bussey of Suitland and of AFL-CIO Local 456 started working nights about a month ago. In an orange vest, Bussey walks along the side of the bridge railing, facing the bright headlights of cars and trucks. Trucks rumbling by at 60 mph make the bridge shift and vibrate uneasily.

Bussey, who has been a construction worker for 18 years, operates a concrete saw that cuts into the existing deck. He expects to be doing the nightly grind for at least four more months and says he does not mind it too much.

But his girlfriend Shirley does. "She wants to know when it's going to end," Bussey said.