From the AP:
Atlanta’s horrendous traffic has inspired two companies that are looking to monitor many more roads and highways than is done today and at a much lower cost. Their approach: Track the signals of cell phones that happen to be inside cars. By using anonymous data from wireless providers to mark how fast cell-phone handsets are moving - and overlaying that information with location data and maps - IntelliOne and AirSage hope to offer more detailed information and pragmatic advice than other firms that monitor traffic through radar, helicopters or cameras. But some critics aren’t so sure the benefits outweigh the potential privacy risks.
Privacy advocates are predictably up in arms over this. But they, and other cellphone users may not have realised that the tracking feature is a fundamental feature of cellular phone networks; they need to know where you are located (or rather, where your cellphone is located) to ensure handoff between base stations. This is why you can continue chatting on your phone even when travelling in a car. This system has been in place since the early days of cellphones!
Those who worry that the "govt is tracking me" seem a bit paranoid, or even "perasan" (filled with self-importance) - as if anyone wants to know that you go to KFC every Tuesday between 1:30 and 2:30pm.
Tracking people via cellphones also has some important uses. A system called Wireless Enhanced 911 is already in place in the US which helps emergency services pinpoint the location of cellphone callers who cannot give directions to where they are.
For example, the "help I'm being kidnapped and I'm in a car boot!" scenario.
I think traffic-tracking is a useful and legitimate use of this built-in feature.
So, if you're really paranoid, try wrapping your cellphone in aluminium foil, or put it in one of those X-Ray film protecter bags which are lead-lined. ;-)