For David Ragno, the Memorial Day weekend is off to an inauspicious start. It is Friday night, about 11 P.M., and the air is unseasonably cold—a harbinger, weather forecasters predict, of a soggy holiday to come. And now this. On New Jersey's Route 202—the highway that the 42-year-old chef uses on his daily Commute—a row of flares funnels the southbound traffic from two lanes into one. Traffic is at a crawl as state troopers check each passing vehicle. "Good evening, sir, are you on your way home?" asks Trooper Ed Dunn, shining his flashlight into the eyes of the driver of the car ahead of Ragno's. "Have you been drinking?" Satisfied the man hasn't, Dunn hands him a pamphlet, How Much Is Too Much to Drink?, and waves him on.

Ragno's encounter is tougher. The traffic office had decided the 10 P.M.-to-4 A.M. sobriety check would subject every 10th driver to an especially thorough examination—an arbitrary system that protects the police from possible charges of discrimination. Ragno's Nissan 300ZX is a 10th car. "May I please see your license and registration, sir?" asks Trooper Jim DeLorenzo. Ragno's registration is locked in his glove compartment, and he fumbles with one key, then another. The beam of DeLorenzo's flashlight sweeps across Ragno's eyes, darts to the dashboard, then back to Ragno's face. "I'm sorry, I can't find the key," says Ragno, his adrenaline surging. "Is this your car, sir?" DeLorenzo asks. Ragno is tense, and it shows. "Please step out of the car," orders DeLorenzo. "Do you know the alphabet?" Ragno nods. Following DeLorenzo's instructions, he places his feet together, his hands at his sides. "A, B, C, D,..." he recites, throat dry, eyes to the ground. For 10 minutes an increasingly uncomfortable Ragno shuffles, trying to avert the stares of passing motorists, as a trooper runs a computer check on him. No violations—save an inspection sticker missing from the windshield. For that, he is fined $20 and allowed to continue. Under his breath Ragno mutters, "This is just another reason I'm getting out of Jersey."

Ironically it may also be one reason he can get out—alive. A few hours earlier, a 42-year-old construction worker was barreling down nearby Highway 78. Troopers say his Buick was going 70 mph when it rammed into a slow-moving Chevrolet, causing the Chevy's gas tank to burst into flames. The speeder, who walked away from his car, was charged with drunk and reckless driving. But the other driver, a 61-year-old woman, was trapped inside her car and died.

The death was one of 451 on U.S. highways over the holiday weekend—about half of them ascribed to drunkenness. In New Jersey, police say, there might have been additional fatalities were it not for the checkpoints. As part of a public awareness program, they say, the checkpoint program helped reduce highway deaths in the state from 1,051 in 1988 to 892 last year. Still, many people object to the program. Civil liberties advocates—as well as drivers arrested on DWI charges—insist the random slops violate the Constitution's prohibition against unwarranted search and seizure. "Just because you're driving at a given place on a given night, say, in a Chevrolet on the night they're pulling over Chevrolets, doesn't make you a suspect in a crime," says Ed Martone, head of the New Jersey office of the American Civil Liberties Union. But Sandy Guritzky, former president of a New Jersey chapter of Mothers Against Drunk Driving, believes the checkpoints are justified. "Is going through a security check to board an airplane unconstitutional?" he asks. "The sobriety checks don't catch a lot of drunks, but the deterrent effect is tremendous." Taking the middle ground, a New Jersey Appellate Court ruled in 1985 that the checks may not be completely random: Traffic officials must be able to explain why they choose a given spot (an unusual pattern of accidents, for example) and give the community prior notice. But the court's decision was vague. A recent ruling, for example, deemed that a sign reading ROADBLOCK AHEAD was sufficient prior notice.

Back on Route 202, drivers seem less concerned about the Constitution than the delay. "The people we stop scream at us," admits DeLorenzo, "they shout and call us names." Dunn, surveying a line of cars that will take at least 15 minutes to pass, is sympathetic: "Hey, can you blame them?" he asks. Indeed, the troopers are the first to concede that the procedure is hardly efficient. "We'll check 300 to 400 cars at each site," says Trooper Gary Jones, who records the license plate number of each car that passes, "but the mobile units get most of the drunks. We'll be lucky if we get one or two a night."

By the time the troopers shut down the checkpoint on this Friday night, the catch will be two marginal inebriates and one certifiable drunk. A young man with tousled blond hair, jeans and sneakers wavers on one foot, head tilted back, counting backwards from 40 to 20. After struggling through the exercise, he is the first to be handcuffed. The second is a young man driving a Ford Mustang. "I swear, officer, I only had one drink," he pleads. "Okay, I swear to God, only two. I'm just tired." DeLorenzo reads him his rights and slaps on the cuffs.

The two men are driven in cruisers to the county's state police barracks, where Breathalyzer tests are administered. The readings fall just short of the 10 percent that New Jersey considers the benchmark of legal intoxication, but are higher than the .06 percent that allows arrest at the discretion of the police. The men are not charged but will not be permitted to drive. If they can't find a ride home, they will spend the night in jail.

The troopers' final quarry is a middle-aged man driving a dark Buick LeSabre Limited who stumbles through his dexterity tests. At the barracks, the pin-striped suit registers .10 percent and is charged with driving while intoxicated. If convicted, he will lose his driver's license for at least six months and pay a fine of up to $500. His annual insurance premium would increase $1,000 for the next three years, and he could go to jail for a month.

For all this, the troopers say, he may be one of the lucky ones. Tonight, at least, he will also be safe. "That," says DeLorenzo, "is what makes all the abuse out there okay." What isn't okay, say critics of the program, is the erosion of personal freedoms in the name of public safety.