Traffic signals equipped with pre-emption systems bear a telltale infrared sensor mounted on top. View Slideshow If you've ever been stuck in traffic longing for a magic box that could turn all your red lights to green, beware: Acting on that fantasy became a federal crime this week.

The Safe Intersections Act, part of the transit bill signed Wednesday by President Bush, makes it a misdemeanor for unauthorized users to wield a "traffic signal pre-emption transmitter," a special remote control used by police, firefighters and ambulance drivers to change traffic lights to green as they approach an intersection.

Lawmakers took an interest in the devices, called mobile infrared transmitters, or MIRTs, a couple of years ago, when it emerged that impatient commuters could purchase rogue boxes online for around $500. Several states outlawed unauthorized possession of the transmitters, and Sen. Mike DeWine (R-Ohio) introduced the federal bill in 2003. The measure won support from police and firefighter groups.

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"When you first look at it, you think, 'It's not such a big deal,'" says DeWine spokesman Jeff Sadosky. "But when you realize the possible implications, somebody using one of these to go 80 miles an hour through rapidly changing lights, you realize it could be life-threatening."

Selling a device to an unauthorized user can land the vendor up to a year in prison; using an MIRT without authorization will carry a penalty of up to six months.

"We agree with the provision," says Gerald Donaldson, senior research director with Advocates for Highway and Auto Safety. "We see how (MIRTs) can be used by people who pose a security threat to American institutions and people."

At first blush, the new law would seem to be a red light for companies like Beeco Sales, which sells an aftermarket transmitter called the Stealth EVP, a tiny emitter that can be clipped to a windshield visor like a radar detector or mounted invisibly behind the grill of a car. But company owner Bruce Erichsen says his network of dealers only sells to authorized governmental users -- the stealth model is for undercover cops, he says.

"I don't want them in the wrong hands," says Erichsen. "I want the police and fire departments in small towns who can't afford what my competitors charge to be able to have pre-emption. It saves lives."

Starting at around $250, Erichsen's MIRTs are still not the cheapest option. Last month, the hardware hacking site I-Hacked.com published plans and instructions for building a home-brew MIRT with a handful of parts totaling less than $20. Site owner Bill Swearingen, a Kansas computer security specialist, says he learned everything he needed to design the circuit from the web. "It's very simple to build," he says.

The devices are essentially infrared strobe lights, says Swearingen. They flash at one of two particular frequencies -- a low-priority frequency used by mass transit just keeps a green light green a little longer. The other, high-priority frequency is for emergency vehicles, and it flips red lights to green, initiating the change cycle within two seconds of activation.

Swearingen says he tested his proof-of-concept device on the streets of Kansas City with complete success before disassembling it to avoid trouble. "I take the freeway to work," he says. "There are no traffic signals." He criticizes equipment makers for not building some kind of authentication into the devices. "Traffic lights are critical systems," he says.

Donna Fleming, spokeswoman for 3M, says the latest generation of the company's Opticom pre-emption system has a security option that allows cities to program their traffic lights to respond only to an infrared signal that pulses an authorized serial number. "Your emitter is programmed into it, so when you trigger this system it recognizes you as an authorized user," Fleming says. "All the systems that we sell have that feature."

Maryland is one of the states embracing the newer equipment, says Thomas Hicks, traffic safety director at the Maryland Department of Transportation. "All of our fire equipment and emergency equipment will now have a coded signal, and the traffic signal itself will have a coded receiver," he says. The state is swapping in the newer, more secure equipment, a process that he says will be done by the end of 2006.

Replacing all the systems nationwide would be a large undertaking. A 2002 Department of Transportation survey found pre-emption systems in use at nearly 25,000 intersections across the country.

The newer systems can also be programmed to log every activation, a useful feature for finding rogue MIRTs, says Hicks. "There will be periodic checks into the number of uses, and if you see spikes in the number of signals, you begin to wonder why," he says.

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