Pinpointing traffic jams is a daily headache for highway departments. For years they've relied on simple sensors mounted at overpasses or embedded in the roadway to relay information back to operations centers. But too often the sensors break down, the advisory signs are useless, and motorists are stuck.
But now a new technology may change all that.
"Today you can actually look at the flow of cellular calls on highways to determine the amount of congestion and what is even more signficant, the speed of travel on those road,"says Oliver Hilsenrath.
Hilsenrath spent 18 years developing radio tracking devices for the Israeli military. Now he runs U.S. Wireless, a Silicon Valley company. His invention uses monitors atop already existing cell phone towers. When drivers talk on their phones, the device tracks the signal, which shows how fast the traffic is flowing.
"It's pretty much like a radar screen," says Hilsenrath. "Every time it sweeps, it adds a target."
Soon highway officials in Maryland and Virginia will begin testing the system along a 15-mile stretch of one of the area's heaviest traveled freeways.
"If the wireless technology can work where we can actually monitor all the different cellular phones out there that are traveling along this particular network and get those average speeds, we'll be able to light that entire map," said Mike Zezesky.
Officials insist that the system cannot identify the caller - that the cellphone user is merely a dot on the screen. But privacy advocates worry about the consequences.
"It's just a short step from that very generalized approach to a very particular approach where particular individuals can be located," said David Sobel, of the Electronic Privacy Information Center
But Mike Zezesky sees the day when drivers will want the information fed into their in-vehicle computer.
"And when you punch in your destination in the computer, it will actually tell you what the best route would be to take," said Zezesky.
But that kind of high tech edge is years away.