Behind the wheel, someone messing with stoplights

Monday, May 14, 2007 | 7:04 a.m.

Las Vegas traffic authorities are concerned that drivers, particularly taxi drivers, are using technology to turn red lights green, a crime under Nevada law - and a crime where it's practically impossible to catch the criminals.

The Regional Transportation Committee is concerned enough about the illegal switches causing accidents and congestion that it's asking police, firefighters and public works employees to reprogram their traffic light technology this summer. It won't catch criminals, but should prevent the crime.

The technology that changes traffic signals resides in two pieces of equipment. The first is a receiver that sits atop traffic lights (the thing that looks like a bird feeder). The second is a transmitter that is usually mounted on the light bar of an emergency vehicle. It flashes invisible pulses of infrared light and , if the rate of flashing is right, the receiver will accept the signal and turn its traffic light green.

Legally, only agencies that respond to emergencies can buy these transmitters. Traffic hackers, though, get their hands on them, usually by deceiving transmitter manufacturers or buying used ones on online auction sites such as eBay. Do-it-yourselfers can build transmitters using instructions available online.

Since 2005 it has been illegal for private Nevadans to own or sell the transmitters. If police catch you with one, they can impound your car and a judge can punish you with up to six months in prison and $10,000 in fines. But because infrared light isn't visible to human eyes, it's awfully hard for the police to spot someone switching a traffic signal.

There is one way to be absolutely sure someone is using an illegal transmitter: Catch him on camera. All digital cameras and video cameras "see" infrared light as bright white light.

(Try it yourself at home: Take a remote control, hold down any button, take a picture with a digital camera - even a cell phone camera will do - and you'll get a picture with a bright light at the tip of the remote.)

As luck would have it, there are cameras watching almost every intersection with an emergency switch. They're there to watch for traffic congestion and are on all the time. To catch people breaking the law, all the government would have to do is set these cameras to save video from a few seconds before to a few seconds after an emergency signal switch.

This is not going to happen any time soon.

In Nevada it's illegal to use a remote-control camera to catch traffic-law violators. Has been since 1999. Police agencies have gone to Carson City for the past two legislative sessions and asked for a change in the law to catch red-light runners. They've lost both times, with lawmakers citing concerns about a Big Brother police state and an epidemic of fender benders if drivers started braking for yellow lights.

Maybe when the Legislature meets again in 2009.

In the meantime, there are only suspicions. Niel Rohleder, assistant traffic manager for Las Vegas, says his staff members have seen vehicles they suspect are illegally changing lights, mostly taxis, although there was one private car and even a motorcycle.

Joe Dahlia, the Taxicab Authority's chief investigator, says he hasn't caught any taxi drivers with illegal transmitters, but, he deadpans, "there's only 6,477 of them, you know."

At the moment, authorities have no idea how many emergency signal switches are fakes.

But 2,500 switches per day seems like a lot (there are more, actually, but older equipment doesn't record switches). Also, some of the switches look funny.

Imagine there's a fire truck heading to an emergency. The emergency is likely a couple of miles away and the firefighters will take major roads to get there. The truck's lights and therefore its signal preemptor will be on the whole time. Because the traffic lights are supposed to be synchronized, if the fire truck has to switch one of them, it will likely switch all successive lights. Therefore, on a log of signal switches, police and fire emergencies show up as a cluster of changed lights.

But what if just one light is changed? Nothing before it, nothing after it, nothing near it. Mohammed Kaseko, a UNLV civil engineering assistant professor hired by the Regional Transportation Committee to study its signal logs, says he suspects these are illegal switches. It's speculative, he admits - single switches could be short-distance runs by emergency vehicles or equipment malfunctions - but if you're looking for traffic hackers, these are signal switches to look at.

If you could. Which you can't.

So, what the Regional Transportation Committee plans to do at its June meeting, says its manager, Murali Pasumarthi, is ask that every receiver and transmitter in the valley be encrypted, which will cost hundreds of man hours and thousands of dollars.

After that, authorities will be able to subtract the number of definitely authorized signal switches from the old suspect number of signal switches. Then they'll know how many times the lights were illegally switched.

And they won't be able to do anything to the people who did it.

The good news is that no one will be able to illegally switch any more red lights to green.

Until, that is, someone figures out how to break the new encryption .