Years ago I made a "real time web based traffic map" for a USDOT/MODOT project. We used traffic sensors made by 3M that sent data to a local 911 center that was also setup under the same project.
The sensors sent traffic counts every few minutes and I used that data to draw greeen/yellow/red lines of the areas covered on a road map.
Thanks man for justification. I'm curious about how currently it being captured.
Yesterday I was driving way home back and there were road blockages due to heavy rain and an accident. I just checked on map for traffic and it's nearly accurate to real traffic of vehicles. My commute routes does not consist of those type of devices/sensors per my understanding and observation. It's non metro city of India.
The sensors sent traffic counts every few minutes and I used that data to draw greeen/yellow/red lines of the areas covered on a road map.
http://multimedia.3m.com/mws/media/362275O/3-monitoring-traf...