Cellphone triangulation (Score 1)

Talking of cellphone triangulation, one could get a much higher sample size by just averaging the movement of the vast sea of mobile phones driving down the road. Almost 100% road coverage without needing shed loads of people to have a GPS enabled phone and the appropriate software.

In fact, Google says that Missouri is one step ahead of me:
http://www.engadget.com/2005/10/11/missouri-to-use-cellphone-signals-to-monitor-traffic/