Google Maps: Traffic

I think I know how Google gets its traffic information. I have a radar detector in my car whenever I drive on the highway and when I pass an on-ramp or off-ramp, the detector goes crazy, only for a few seconds, and only on the K-band (the CHP uses Ka-band). The detector going crazy must be the radar guns mounted on light posts which somehow relay the information back to CALTRANS or Google themselves when is then used to update the Google Maps Traffic pages.

I don’t think this is done with GPS or wire loops in the ground but it might also be done with CALTRANS FasTrak transponders. Those are little boxes you put in a car which is an electronic toll collecting thing. The FasTrak boxes use RFID as their primary means of telling the toll collecting machine that you’ve gone over a toll road.