Originally Posted by MrFloppy
Most Sprint phones come with Sprint GPS. When you fire it up, it asks if you want to anonimously report info back to Google.
What it does is report your speed over Sprint's data connection. So, if you are on an Interstate, and you are doing 20mph, there must be heavy traffic.
So that's one way.
that was actually one of my thoughts - i didn't think about smartphones, but i thought maybe those cars with factory-designed GPS systems that can also receive traffic reports also transmit back your car's telemetry.
thanks for your observation about Sprint - did not know that one.