How does Google Maps get the traffic information
How does Google Maps get the traffic density information for its travel maps?
Google maps has a fantastic feature that not many people seem to be aware of. You can enable real-time traffic information on Google Maps and this feature is available Worldwide!
I first discovered the London travel map through http://www.londontraffic.org/. I was then startled to discover that once I zoomed out, to France, the information was still available and it changed dynamically every time I refreshed the page. I then discovered it was available everywhere, in places that plainly would not have traffic monitoring systems linked to the Internet.
After much head scratching I worked out how they do it. They just monitor the information being transmitted by users mobile phones. Most modern phones have GPS and can locate the user to within a few metres. Certainly accurate enough for measuring traffic density.
How to enable traffic reports in Google Maps
To enable Google Travel, go to Google Maps, click the menu hotdogs (usually top left) and select Travel
Google Maps traffic flow information works both ways
If you are zoomed in close enough you will see that the traffic flow rate is shown in either direction.