Google Maps has gained a new feature which appears to be active now, at the very least for the US and UK. Upon looking up driving directions, you can swipe up on the lower bar right before starting your trip to check if the travel time will change over the course of a few hours.
Swipe up to see more info
This is especially useful when trying to head somewhere around rush hour. Maps will show you a visual as to convince you it might be better to leave to your destination an hour from now to avoid traffic. Googles next step should be to add this feature for those in metropolitan areas who depend on public transit. In fact, HereWeGo maps already does this.
Do you find this feature useful? If youre outside the US or UK, let us know if its working for you. Also, do let us know if it works on iOS.