Metro Traffic adds tens of millions of virtual traffic reporters via cell deal.

From "Inside Radio" for August 5th....

Metro Traffic adds tens of millions of virtual traffic reporters
via cell deal. Westwood One’s Metro Traffic and AirSage partner
to use cell phone signals to provide faster alerts, more
reliable travel times and better alternate route suggestions.
AirSage compiles anonymous data from signals sent from 53
million Sprint Nextel mobile phones on traffic flow and speed.
AirSage’s network covers 150,000 miles of roadway, compared to
fixed-traffic data sensors, which monitor real-time traffic for
about 7,000 miles of interstates. The new reporting technique
will begin rolling out next month.

What a great idea. Typically folks have been dependent on getting traffic info from the sensors that folks like CalTrans puts in the road bed.

I would expect that the technology wouldn't be too complex to do this. You just need to track when a particular cell phone gets handed off between cell sites. Since the tower locations (Lat/Lon) are known, you can determine speed. You can even use the Inverse Square Law and smooth out the signal strength the cell site is getting to see how fast someone is going towards or away from a cell site.