Debbie Proffitt operates a weigh station on one of life's highways. She works the midnight shift, and what she weighs are trucks, thousands of them, Macks and Freightliners and Internationals, gleaming pack mules of the superslab.

All night long, the trucks gear down and pull off Interstate 95, line up on a ramp between the exits for Dale City and Dumfries in Prince William County, ease onto three concrete-covered scales that handle 100,000 pounds, no sweat. Rain is falling lightly, and headlights glow against the asphalt like high-watt eyes, and the music of horsepower filters through the tinted glass and into the tower, where a radio is set to country.

Proffitt, 29, perches on a high chair in her tower 25 feet above the northbound lanes, popping Juicy Fruit and smoking Salems. From here she controls traffic bound north and south. As each rig pulls in, she watches the weight on the Digitruck readout, then flicks a toggle switch and hits a counter. Click, dit-click means a truck has gotten the green. A crackling voice through the intercom means a summons from the highway department.

"Driver, pull into the parking lot," Proffitt intones. "Bring all your papers and your trailer tag and come in through the tunnel." Then she calls down a spiral ladder to her partner. "Got a southbound, Smitty." On this night, Proffitt will click, dit-click 1,974 trucks. Twenty-two others will be met with her voice.

Last year, more than 7 million trucks rolled over the scales at Virginia's 15 weigh stations. Almost 45,000 of them were overweight, and their fines totaled more than $4 million--an average of less than $90 a truck. The fines are the state's way of enforcing the 80,000-pound maximum load limit for tractor-trailers, imposed primarily to keep the wear on roadways to a minimum. According to state calculations, a truck with the legal limit of 20,000 pounds on its front axle does the damage of 9,600 cars.

Dumfries is the busiest of the stations. Seven days a week, 24 hours a day, it is the highway department's version of a radar trap, only the truckers are required to go out of their way to run through it. And if they are passing between midnight and 8 a.m., chances are they will encounter Debbie Proffitt, known by the state as a Weigh Party Technician, known by the truckers as the girl in the chicken coop.

Proffitt isn't exactly loved by the drivers who pass her station, men out of North Little Rock or Milledgeville, Ga., or Kingsport, Tenn., pulling absorbent materials or Best Products or a piece of a mid-section of a submarine. It's nothing personal. She is the law when they are wrong. They act surprised or they act resigned or they make excuses. They say they had to stop short for a car and their load shifted. They say the company made them haul an overweight load. They say they took on ice or fuel. Sometimes they get downright nasty. One driver asks if she doesn't have anything better to do than badger a man trying to do his job. Another tells her he's certain the Easter bunny didn't visit her.

But to Proffitt, "There are no excuses. It's all after the fact. Maybe something did happen, but it doesn't matter as far as the tickets are concerned. They can tell it to the judge. I keep the discussion to a minimum." When she says this, she half-smiles, half-frowns. The dimples show and the tone is somewhat apologetic. After all, a driver's headache is his own fault. This is just her job, $15,000-a-year, money for the payments on her snow white Trans Am, and for dog food for her Belgian shepherd.

She lives with their inevitable deceptions. Sometimes drivers try and hang one wheel off the scale so they will register lighter. Sometimes they pull over and collect a convoy to assault the scales en masse and cause a backup. The empty or light trucks come in first, the overweight ones follow a distance behind. The light ones leave gaps between their rigs, hesitate when they get the green light, or drive at a snail's pace, all of which creates a dangerous backup on the highway. When this happens, Proffitt has to give them an automatic green, as she did the other night when she let 55 southbounders pass through unweighed in 13 minutes.

Proffitt has been on the job for eight years. She quit studies at Old Dominion University after 2 1/2 years to have surgery on a trick knee that would sometimes just pop out and leave her in a heap on the ground. She was studying sociology, and this was to be just a part-time thing to get her through her recovery. But the graduate of GarField High School in Prince William says she decided to blow off college, "because I liked working and having money and wanted a car and didn't like school."

There has been some excitement through the years. Sometimes the Budweiser Clydesdales come through in their trailer. Once a mobile production of the television show "Moving On" passed through, shiny enough to eat on. Another time she met the roadies from the Charlie Daniels Band. They were hauling the band's equipment to a concert down south in two jet black tractor-trailers with enough chrome to light the night. She stopped them just for a chance to catch a glimpse of Charlie. He, unfortunately, had flown on ahead in a private jet.

Besides the occasional ghostly footsteps said to be those of a trucker who died in the tower after shifting his load of fertilizer on a sweltering summer day, Proffitt has been visited by the driver's education students from Quantico High School, countless packs of Cub Scouts, and a woman whose husband left her at the nearby rest stop. Seems the woman was sleeping in their camper, and when her husband stopped, she woke up and went to the bathroom. Thinking she was still asleep, he drove off, not to discover his loss until North Carolina.

Once another woman walked in and locked herself in the bathroom. When the state trooper stationed at the tower tried to get her out, she opened the door and threw lye in his face. And Proffitt is often visited by a trucker who finds the musty tunnel beneath the interstate perfect for making recordings of his truck-driving songs.

But these events are few, and mostly there is just the shining lights and the revving engines, soulful country on the radio and the constant click, dit-click of her toggle switch and counter. "I know this sounds strange, but I really like my job," Proffitt says. "Sometimes it gets boring and obnoxious, but it's kind of like I have a hold over the highways. It's like a game. Me against the drivers, but the cards are marked and I usually win."