Joseph Averkamp collects stories about how people break the law. He keeps them in a Powerpoint presentation, dragging the grainy local news photos into the slides. There’s the guy who stuffed a pile of wooden boards into a hoodie. The Washington man who buckled up next to a cardboard cutout of Dos Equis' "Most Interesting Man" mascot. Another one he could add, but hasn't yet: The dude who stuck a yuge picture of Donald Trump's face on the headrest of his passenger seat.

All attempts to trick the authorities and sneak into that highway VIP zone, the carpool lane.

Averkamp is Xerox’s senior director for technology policy and strategy (yes, the copier company is in the transportation business), and he has a tool, first introduced in 2014, to bring those breaking the sanctity of the carpool lane to justice. This month, he has numbers to back it up—mostly.

Crime in the Fast Lane

Over the past three decades, agencies around the country, hoping to bust traffic, have turned to high-occupancy vehicle (HOV) lanes. Reserving less congested space for vehicles with multiple passengers encourages carpooling, or so the theory goes.

In some places, the lanes are open to electric vehicles, to encourage zero-emissions driving, or reserved for those who pay extra, to keep the city coffers stuffed. In transpo-speak, these are HOT—high occupancy toll—lanes.__ __

Yet, as anyone who's driven on a highway with an HOV lane knows, cheaters lurk behind the wheel. During a brief 2015 pilot program on a state highway, Xerox found nearly 12 percent of HOV users were lying liars. One stakeout in California nabbed 241 carpool fakers in a single day.

“Enforcement, especially if you have that occupancy component, is an important aspect,” says Christopher Tomlinson, the executive director of Georgia’s State Road and Tollway Authority. “Even if we have a low percentage of violators, it’s not fair to those within the system.” Six to eight percent of the drivers on his state's 16-mile tolled express road don't actually pay to be there.

Swindlers erode faith in the HOV lane, which can destroy the premium driving experience along with its goals of getting more cars off the road and reducing vehicle emissions. In the past, governments have depended on old-fashioned stakeouts and the naked eye to catch fraudsters. But new techniques are changing the state of the left-most lane.

X Marks the Spot

Xerox’s imaginatively named Vehicle Passenger Detection System uses two cameras, an illuminator, a video image processor, and a laser trigger. When a car speeds by at up to 100 mph (a different crime), the cameras capture its front and back, including the license plate.

Using geometric algorithms, the system determines whether there are enough people in the car to qualify for the HOV lane, and bust accordingly. “We tell it that that dog you see isn’t an occupant, and the baby in a car seat is an occupant,” says Averkamp. (Warning: If your unfortunate child looks more dog than baby, the system will have a hard time.)

The company says that during a three-day pilot last year, the system caught 78 HOV violators per hour on a stretch of California’s I-5, with a 95 percent accuracy rate. That’s a lot better than roadside observers equipped with only their eyes, who, according to Xerox, spot just 36 percent of violators on that stretch of road.

Images captured by the front and rear cameras of Xerox's Vehicle Passenger Detection System. Xerox

Because it’s not perfectly accurate, Xerox recommends personnel manually inspect the images of the alleged rule-breakers before mailing a bill to the address on the vehicle’s registration. The infrastructure will cost about the price of an electronic tolling system, says Xerox, but price is highly dependent on a municipality’s needs. (For comparison’s sake, Massachusetts is shelling out $130 million for one of those.) The system has been piloted in eight locations around the world, but has not been permanently installed yet.

Municipalities eager to purify their lanes have other high-tech options. On the 16-mile stretch of Georgia I-85 that uses HOT lanes, drivers who haven’t paid via transponder can get photographed by a roving band of speed camera-equipped cop cars. The system there alerts police when the car hasn’t paid, and it’s the "license and registration" dance from there, which usually ends with a $150 fine.

Fighting Cheaters by Design

There’s another way to discourage lane abusers from drifting into forbidden places: smart design. Research coordinated by the federal government’s National Cooperative Highway Research Program finds it’s harder to cheat when the special lanes are separated from general traffic by a physical, concrete barrier.

That eliminates the most tempting kind of cheating, the brief foray over the twin white lines: I know it's wrong, but I'll get right back to my lane—just after that bottleneck up ahead!

Okay, perhaps duh. But a barrier does more than repel swindlers, the researchers found. It made vehicles in the managed lanes move faster. "If you’re driving on the managed lane and you see stop-and-go [traffic], you’ll worry that someone will jump into your managed lane," says Yinhai Wang, a transportation engineer with the University of Washington who headed up the federal study. Drivers separated from the hoi polloi by a physical barrier feel safer going faster. Of course, concrete barriers cost money.

Tomlinson, the toll road director, says enforcement is worth the cost. When rule-abiding drivers see people ducking the system, they become disenchanted. When you’re trying to convince people to do something vaguely unpleasant or inconvenient—like trading their solo commute for a carpool, or paying extra for privilege of moving faster—they’re customers. Keep 'em happy.

And what makes the self-righteous carpooler happier than seeing that solo cheater brought to justice?