Nineteen-ninety-four was a harrowing year for then-Seattle resident Demetrius Thompson. First he was rear-ended. Then he was struck while walking across an avenue by a car running a red light. Fortunately, neither accident was serious. But in both cases the driver had been talking on a cell phone – and that gave Thompson an idea.

Twelve years later, he’s finally ready to show that idea to the world: it’s a system that uses the Global Positioning System (GPS) chips lodged inside many cell phones to track a vehicle’s coordinates. Whenever a driver who’s talking on a phone closes to within 100 meters of a stoplight, the system interrupts his or her conversation with a loud chirp – providing a not-so-gentle reminder to slow down. Thompson (now living in Los Angeles) has demonstrated a prototype to city engineers and set up a company, Global Mobile Alert, to market the idea to cellular carriers, who could offer the warning system as part of a growing array of data services available to mobile subscribers.

“It’s about saving lives,” says Thompson, who has worked fulltime on the project since 1994. “If you’re driving and talking on your cell phone, you’re not really paying attention to what’s going on in front of you. But when you hear that mobile alert chirp, it’s going to bring you back to reality and give you a good 7 to 10 seconds before you will be at an intersection.”

Thompson’s demonstrations have been limited so far to the West Hollywood neighborhood of Los Angeles. But if the idea attracts interest, it will join a number of other traffic safety technologies being tested in cities across the country. In Michigan, for example, Motorola has experimented with a wireless system that would warn drivers when vehicles ahead of them are slamming on the brakes (see “Wireless Highway,” March/April 2006). But such experiments usually involve adding new equipment to cars, such as accelerometers, wireless transmitters, and GPS receivers – and they wouldn’t work in practice unless all vehicles were similarly equipped.

The only requirement for using Thompson’s system, however, is a GPS-capable cell phone. The phone compares signals from GPS satellites to determine the vehicle’s location, direction, and speed, and transmits that information over the cellular data network to a computer server built by Global Mobile Alert. The server contains a database with the exact latitude and longitude of all stoplights and other traffic hazards in the driver’s area. If the server calculates that the cell-phone user’s vehicle is nearing one of those positions, it sends a chirp resembling the cuckoo-clock sound played by some pedestrian-crossing systems for the benefit of the visually impaired.

Jim Carlin, a strategic account manager at market research firm Frost & Sullivan, has reviewed Global Mobile Alert’s technology, and says it would be natural extension of cellular telephony’s original purpose. “If you look back 10 or 15 years when cellular was still growing, one of the key selling points was that a cell phone would help you get aid if you are involved in an accident or a crime,” Carlin says. “It’s a way of enhancing safety when you’re out there on the road. By going back to those roots, Thompson may be hitting a sweet spot.”

It’s a spot that needs hitting. Driving remains the most dangerous form of mass transportation. For every 100 million miles Americans drove on interstate highways and other non-urban roads in 2003 (the most recent year for which data is available from the U.S. Department of Transportation) there were 2.3 fatalities. That was nearly eight times the airline industry’s rate of 0.3 fatalities. (Urban traffic is somewhat less hazardous, with 0.93 fatalities per 100 million miles.)

According to the National Highway Traffic Safety Administration, 80 percent of highway accidents involve driver inattention within a three-second period preceding the accident. The agency does not track how many of the drivers in these accidents were using cell phones. But a study released last year by University of Utah psychologists David Strayer and Frank Drews showed that talking on a cell phone while driving may double the risk of getting into an accident.

That’s because drivers who are absorbed in phone conversations are simply slower to respond to events on the road. In studies using driving simulators, Strayer and Drews found that drivers talking on cell phones took 18 percent longer to react to brake lights on the car in front of them. Even among 18- to 25-year-olds – the group expected to have the fastest reflexes – talking on a cell phone reduced alertness levels to those of 65- to 74-year-old drivers.

Twenty-six states have enacted laws that either ban drivers from using cell phones while driving, or, more commonly, restrict them to using hands-free devices, such as the Bluetooth wireless earpieces now available for many cell phones. And the National Transportation Safety Board (NTSB), which is charged with investigating major transportation accidents, recommended to all 50 states in 2003 that novice drivers – those who have had driver’s licenses for less than six months – be banned from using any electronic device while driving, including cell phones, pagers, and PDAs. “We’ve known for years that novice drivers need to limit distractions,” says Ted Lopatkiewicz, NTSB’s director of public affairs. “And, frankly, we see drivers who are not teenagers on the cell phone – and they shouldn’t be using it either because it is distracting.”

But the NTSB doesn’t have enough data on accidents involving drivers talking on cell phones to issue a blanket recommendation against the practice, Lopatkiewicz says. And, in any case, regulators and legislators would have a hard time stamping out a habit that’s indulged in by tens of millions of drivers every day – and is highly profitable for the carriers who sell all those expensive daytime minutes to commuters.

And that’s why there’s a niche for technologies that make it safer to use cell phones while driving, says Scott Fischler, an energy and transportation consultant in Palm Springs, CA, who’s working with Thompson to market his mobile alert system to cellular carriers. “This is an alternative to some of these reactionary laws banning cell phone use by drivers, where everybody is being penalized for the mistakes of a few,” says Fischler. Thompson’s technology would be useful, he says, because it would give drivers an unavoidable warning of upcoming hazards. “It’s obtrusive enough that you simply cannot ignore the fact that you’re approaching an intersection, but it’s not so disruptive as to prevent you from having a conversation,” says Fischler.

According to Fischler, Global Mobile Alert is in discussions with several cellular carriers about building a nationwide network of servers and adding the alert system to wireless customer’s existing data services – for a monthly fee of course. Insurance companies have also shown interest in the technology, Fischler says. They could attract customers by offering a safe-driver discount to drivers who subscribe to the service.