It's the middle of the night in front of the Department of Commerce building at Constitution Avenue and 14th Street NW. Suddenly, a flashing, whirling orange light slices the darkness and the quiet is invaded by a loud rumbling.

A vagrant, stretched out on a bus shelter bench in front of the building, sits up and gawks as a huge yellow machine rolls slowly down the street toward him, riding against the northside curb of Constitution Avenue. Spraying water and gathering up beer and soda bottles, newspapers, candy wrappers and the rest of the day's debris, the diesel-powered "road sweeper" looks like a giant three-dimensional Pac-Man.

Inside the sweeper, driver Curly Washburn leans out a window, rests his arm on the edge and smokes a cigarette while he steers the machine. A tall, slender man with thick, salt-and-pepper hair and matching mustache, he has worked at the D.C. Department of Environmental Service's Street and Alley Cleaning Division since 1965.

He has worked at night for 12 years, part of a team of six sweepers who converge on the city's downtown section each weeknight. They sweep at night instead of during daylight hours because there are fewer parked cars blocking the curbs.

The vagrant waves at Washburn and smiles, flashing a mouthful of decaying teeth. For those who live on the streets, the sweeper is as close as they get to a personal maid.

By virtue of his mole-like lifestyle, Washburn, 52, sees a different side of Washington than most people. To him, the city is shadows, street lights and waste. Vagrants, prostitutes and police are regular sights in his world. The famous marble buildings and monuments that line his downtown route are merely nameless edifices whose curbsides need tidying up.

He enjoys the immediate gratification inherent in his job. "You know what you've got to do and you do that. You see the dirt and you clean it up. And nobody bothers you. The supervisors don't ride your back," says Washburn. He is a man who savors his freedom and even bought 25 acres of land and built a house in Culpeper, Va., to enhance and preserve it. He drives 196 miles to and from work.

The worst part of Washburn's job, he says, is the rough ride inside the sweeper. There are no shock absorbers on the monster, which does the work of 10 men. The slightest bumps in the the road cause tremors that keep the driver bouncing in his seat like a basketball. "Because of the nature of this job, I do think that we should be graded higher than we are," says Washburn, who is paid about $25,000 a year. "After bouncing around like this all night, we deserve every penny we get."

Another drawback is the low status of his job. He says he is often jeered by crowds of bystanders and called derogatory names. But, Washburn says, "I look at it like this: It's a job. It feeds and clothes my family."

The machine he drives is equipped with two steering wheels and a dual panel of levers that resemble electronic game "joysticks." Washburn uses the levers to maneuver the awkward-looking machine around corners and zip skillfully around parked cars. He refills the sweeper's 100-gallon water tank at curbside fire hydrants.

Crawling along at speeds of about seven miles an hour, the machine is guided by two wheels joined together at the rear. Two circular brushes made of thousands of steel bristles are attached to either side of the sweeper. The brushes can be adjusted to fit the curb angle. The left brush spins quickly in a clockwise direction and the right one spins in the opposite direction. Each propels trash and dirt inward into a trap beneath the machine that is composed of three parts--a vertical conveyor belt with wedges, a triangular-shaped steel bar that points toward the belt and a long, cylinder-shaped brush that looks like a giant hair roller and is positioned in back of the belt.

The sweeper machine simultaneously conjures up fearful images of a combat landing craft and a harmless, gigantic algae eater. Moving slowly down the street, leaving a trail of water behind, it sometimes resembles a giant snail.

Sweepers scoop up everything from paper bags to leaves to broken and discarded automobile exhaust pipes. "Some drivers hate to see the trash," Washburn says. "But it doesn't bother me. Because if nobody threw it down there, I wouldn't have a job. But I hate to see them throw it down there right after I clean the street. I wish they would wait until the day to do that."

At the dumping site near South Capitol and Fourth streets SW, about three blocks from the department's garage at 900 New Jersey Ave. SW, Washburn deposits hundreds of pounds of debris on a single night. In the shadows of the night, the wet mound of waste looks like some hairy thing excavated from the bottom of the sea.

"All in a night's work," says Washburn.