Traffic police could be anywhere. Waiting in the grassy median. Lurking underneath overpasses. And now they are even perched atop a harmless-looking state highway mower.

What will those champions of compliance think of next?

In Frederick County, the Maryland State Police are teaming with the State Highway Administration in a clever -- some might say sneaky -- experiment to catch speeders. Maryland has been under heavy pressure from the federal government to reduce the number of speeders; 76.2 percent of motorists in the state early this year were found to be exceeding the 55 mph speed limit, while the national norm is 56 percent.

State police have responded with several crackdowns, including rolling roadblocks, but the Frederick plan, the first of its kind in the state, involves placing officers with radar speed detectors in yellow mowers, dump trucks and other heavy equipment along the busiest highways. It is one of the few techniques police are eager to publicize; the mere chance that an officer might be hiding at a construction site may force drivers to slow down, they said.

"I believe very strongly in that air of omnipresence," said Lt. Allen Swope, commander of the 52 sworn officers attached to the Frederick County State Police Barracks. So far, the program, launched this month, has been used only a few times.

One afternoon last week, Trooper 1st Class Frank Woullard sat in a bright yellow, 18,000-pound state highway truck parked on the shoulder of busy I-70, a few miles north of the city of Frederick. His regulation tan police hat rested on the seat beside him.

Using the truck's rear-view mirror, Woullard checked the stream of afternoon traffic against the digital speed readings of a radar unit in his lap. He relies on his judgment as well as the radar in catching speeders, he said. Several cars passed -- at 59, 56, 62 mph -- then Woullard lifted a walkie-talkie to his lips.

"Got a green Buick coming up in the fast lane going 70," Woullard radioed to his partner, Ed Syracuse, who was waiting a quarter-mile ahead in an unmarked car.

The driver of the green Buick haplessly zipped up the highway, ignorant of the spy in the yellow truck. Syracuse, in full uniform, took a step into the road, pointed at the Buick, then pointed to the shoulder. The driver pulled over.

"Anything over 55 is vulnerable," said Woullard, 34, who has 13 years of police experience.

What state police do not like to publicize, however, is that motorists driving below 65 are usually left alone in order for police to nab the more lead-footed offenders. Unofficially, the individual trooper makes the decision about exactly how much speed is too much.

Some speeders scraped by with just warnings on this afternoon, but not the driver of the green Buick.

"Seventy miles an hour? Sure, I gave her a ticket," said Syracuse, 21, after issuing a $40 citation.

The driver sat woodenly behind her wheel, waiting to reenter I-70. "This is the first ticket I've gotten in 15 years of driving," she said. Did she deserve it? "Absolutely not. It's the sneakiest thing I've ever heard of, hiding in a truck."

But state police say the strategy is effective. Troopers in neighboring Carroll County are making plans to start a similar program after Labor Day, and officers in other counties are considering the technique. State highway officials are in favor of the plan because it reduces the danger to their construction crews.

"We don't want to cause the public any problems," said John Anders, assistant district engineer State Highway Administration assistant district engineer, "but . . . they do speed through our work zones, as well as on the rest of the highway."

Swope said there had actually been a slight decrease recently in speeding tickets along well-traveled Rtes. I-270, I-70, 15 and 340. Last year, Frederick County troopers wrote 7,917 tickets to drivers who sped past 55, he said; an additional 2,357 tickets were written for other speeding violations.

"When we use the highway equipment, the CB radio chatter is phenomenal," Swope said. "That convinces me the program is working and the word is getting out. People say things like, 'Hey, there's a piece of state road equipment. Better watch it.' "