Those toll-paying radio tags glued to millions of American windshields-four million in the New York metropolitan area alone-are getting more and more roles. In many areas they double as traffic counters, and in a few pilot projects they allow drive-thru debiting of McDonalds purchases and airport parking fees. Now, they’re getting their toughest-and most controversial-job yet: helping law enforcement officers decide which tractor-trailers to pull over for inspection.

Normally, freight-hauling trucks face the random chance of a mandatory stop at a highway weigh station. There, police check the truck’s weight, its safety equipment and the driver’s logbook. But in a Maryland pilot study, truckers will have the option, when buying a regular toll tag, of instead getting a new “fusion” tag. The new tag pays tolls just like the old ones. But there’s a key difference: the tag carries a second set of protocols to communicate with a roadside scanner as the vehicle approaches a weigh station.

The scanner relays the truck’s ID number to the station ahead where a police officer checks safety databases for information about the truck and its corporate owner (though not the driver, due to privacy concerns). At the same time, a “weigh in motion” sensor embedded in the pavement records weight on the fly. Within seconds, the officer makes a decision and beams a signal back to the tag. For trucks with clean histories and proper weights, the tag flashes a green light: keep on truckin’. Riskier rigs get the red: pull over for inspection. Good truckers are spared needless stops; police operate more efficiently.

Such pre-screening systems are already being used in some parts of the country. But these existing systems use transponders built only for weigh-station screening, not tolls. Adoption has been slow; only 200,000 of the nation’s three million trucks carry these screening-only transponders. Transportation officials believe that adding the screening function to popular toll tags-starting with the E-ZPass system in seven northeastern states including Maryland-will bring them into far wider use.

And so the Maryland experiment is being closely watched as the first 3,000 fusion tags are readied for distribution this month; for starters, they’ll only be checked at a single weigh station along I-95 in Perryville, MD.

This modest beginning is the first step toward a unified nationwide transponder infrastructure. In such a system, a single tag pays tolls everywhere, spares good truckers needless inspection stops and enables police to focus on higher-risk trucks, says Madeleine Marshall, program manager of the Intelligent Transportation Systems program at the Johns Hopkins Applied Physics Lab in Laurel, MD, which is developing the Maryland system.

“It’s been a long time coming,” she says. “The grand vision is that trucks traveling throughout the continental U.S. will have one transponder on the windshield for tolls and for electronic screening.” This could take five years, and initially will focus on the congested Northeast zone covered by E-ZPass, she says.

Lukewarm Welcome

But not everyone is enthusiastic. Truckers are wary that toll tags, which until now have had the sole purpose of helping them avoid tollbooth traffic jams, will become a tool to help police slap truckers with violations. “They are attempting to use electronically collected information as an enforcement tool, and we have some serious concerns with that,” says Mike Russell of the American Trucking Association, a Washington-based trucking trade group. “It smacks of Big Brother, and Big Brother hasn’t been authorized to do this.”

For now, anyway, Big Brother is being held at bay, says Rich Taylor, director of information systems for the Intelligent Transportation Society, a Washington-based consortium of government agencies and private companies that develops transportation technologies. That’s because participation will be voluntary, he says, with truckers having the option of getting the original E-ZPass tag without the screening function.

Taylor sees a boon to truckers. “It could be very significant, because it provides the trucking companies, at least in the Northeast, the ability to have common accounts and reduced transponder costs. And it takes up less room on their windshields.”

Of course, the initiative raises the question of whether cars, too, will one day be subject to toll tag-based spot-checks of registration and inspection information. After all, in many regions the infrastructure already exists; tag-readers are installed not only at tollbooths, but also along highways, where authorities use them to count cars and detect traffic jams (see “The Road Ahead”).

Not to worry, says Taylor. Transportation planners know that linking car toll tags to policing would prompt drivers to tear them off windshields and resume pitching quarters into baskets. That’s why states have resisted the temptation to use tag readers as speed traps, he says.

In any case, car drivers simply don’t face the sort of random checks for weight limits and safety as truckers. So it seems likely that with ordinary car toll tags, you probably won’t ever get screened. But you might get fries with that.