Play around in the account settings long enough and you find the creepiest things, such as the fact that Google knows where you go whenever you have your device on you. It does make sense, given how high quality the real-time traffic directions are when using Google Maps to navigate.

If everyone with a Google account is tracked while in motion, as well as Google knowing the likely destinations of everyone on the road based on a combination of active navigation and your personal likely destinations by time of day, then Google knows very well what the flow of traffic is likely to be.