How does my iPhone (iOS 9) know that I'm about to drive home? Since iOS 9, every time I get in my car and start it, I receive a notification that I can expect an x minutes drive to my home. How does the phone know that I'm driving my car?

Does it detect motion without footsteps? Does it know I just drove to that location and assumes that if I move away from it, I'm in my car again? Does it recognize that it has connected to my car's phone system via bluetooth?

The reason I'm suspecting the latter is that I got such a notification when my wife got into our car (which both of our phones are connected to) and drove away (while I walked away from that location). Anyway, I'm curious about how Apple pulled this off...
Does it recognize that it has connected to my car's phone system via bluetooth?


This. Precisely this.

It also works if you connect the device to your car system over USB (not just charging, but actually connected to receive phone calls), or start CarPlay if supported by your car.