BELMONT — When police Sgt. Richard Mann briefed his team of 16 officers before they conducted a sobriety checkpoint overnight Friday, he defined a successful operation.

“I hope we don't catch any drunk drivers tonight,” he told the regional DWI task force members. “That would mean we've been doing our job well.”

About an hour later, however, Mann's hopes were dashed.

After dozens of drivers passed through the checkpoint along busy Route 3, a man driving an SUV was pulled over in the westbound lane. When the motorist opened his window, an officer smelled booze. The driver's words were garbled in answering police questions, and when he was asked to get out of the car, he stumbled as he opened the car door. A few minutes later, he failed a field sobriety test.

He was helped by two officers across the street into the state's DUI Mobile Command Center, where he was charged with drunken driving.

“He clearly couldn't operate a vehicle, he couldn't do much at all in that state,” Mann said.

Man noted what could have happened had he not been stopped.

“You look out there at the cars on either side of him, there were kids and babies in those cars,” Mann said, shaking his head.

Police had publicized the sobriety checkpoint for months. Stories about it ran in newspapers. Notices of it were posted on beer coolers at local stores, at area bars, and on convenience store gas pumps. There was a flashing sign warning of it placed along area roads. Police didn't give the time or the place, but cautioned drivers that a checkpoint would be in the area from June 17 to 23.

The task force comprises officers from the Belmont, Northfield, Tilton and Sanbornton police departments. Each department has run checkpoints over the past few years, Mann said.

This checkpoint, about a mile west of the Laconia line, was set to run from 9 p.m. Friday to 3 a.m. Saturday on one of the busiest roads in the Lakes Region, with 20,000 cars passing each day. It was placed within a quarter-mile of seven restaurants with bars, a state liquor store and several convenience stores, Mann said.

The team's command center was a motor home-sized, all-in-one drunken driver processing vehicle, complete with a Breathalyzer to measure the level of intoxication, video cameras, communications stations and jail cells. It straddled the road, and its tall light towers made it seem like daylight below.

The checkpoint site — which took up about 300 feet of road — was cordoned off using signs, cones and police vehicles. It had two lanes in which vehicles were stopped and two lanes for vehicles to pass through if the checkpoint was busy.

Mann said motorists should be stopped for no more than 30 seconds.

“We stop as many as possible, with the least invasiveness possible,” he said.

Amid calm chatter among colleagues, officers waving lighted red wands directed motorists to stop. Behind those officers were others prepared to assist.

“How we doin' tonight?” an officer asks one driver, who quickly finds his license and registration as the officer explains why he was stopped. “Have a great night,” the officer says as the driver, seemingly unfazed, drives away.

For the most part, despite the heat, the humidity and the occasional cranky driver, the officers mostly smile as they just check licenses and registrations. Most drivers seem more irritated with having to find their documents than with the police officers, and sometimes the stops take longer than 30 seconds. Some of the drivers thanked the officers when leaving, others grumbled.

When an officer suspected a driver of being under the influence, other officers would gather around the vehicle. The driver would be directed to exit the vehicle, and it was searched for evidence of drug or alcohol use. A local court official was available all night to issue search warrants.

During one stop, an officer smelled the aroma of marijuana coming from a car. When the driver got out, a bag of pot fell to the road, and he was arrested. Another man was later arrested after trying to hide a bag of marijuana in his shoe.

One driver who seemed to have his coordination and wits about him was asked to get out of his car and promptly failed both a field sobriety test and a Breathalyzer test. Awhile later, he hugged his female companion in the parking area, then dialed his cell phone as an officer drove his car to an impoundment area. Charged with DWI, he didn't want to discuss the incident with a reporter.

At 1:45 a.m. Saturday, there were fewer cars passing or being stopped, but the command center's two jail cells, which hold three people each, were full, Mann said.

“It's been a busy night,” he said.

By the time the checkpoint was dismantled at 3 a.m., police had stopped 330 vehicles and had made four arrests for drunken driving, four arrests for drugged driving and one arrest of a person on a U.S. immigration charge. In addition, 28 drivers had been cautioned about vehicle safety issues.

“Actually, that's about what we had last year,” said Mann, sounding disappointed.

But he remained optimistic about the checkpoint's mission.

“If we stop a drunk or drugged driver, we've done a good thing. But with the publicity and the awareness that comes with these checkpoints, there's a deterrent effect. We stopped some people, but who knows how many people didn't drink and drive this week because they heard about the checkpoint? That's what we hope for.”