It seems that when you're trucking along (in the USA, UK, France or China, at least), navigating using Google Maps on your smartphone, you're actually helping crowd source traffic data for Google, i.e. the application is reporting back to Google on your position and speed, a process described here in detail. While there are possible privacy implications in this, it does seem an interesting approach - or at least it would be if there were enough people using the system - so far in the UK, only motorways seem to be tagged for traffic status. Comments welcome.