Directions button

Indicates the estimated travel time to the destination from your current location, using either transit directions when the Transit map is selected, or your default mode of travel (driving , walking , or cycling ) when the Explore, Driving, or Satellite map is selected.

To select a different map, tap the button at the top right. To change your default travel mode, go to Settings  > Apps > Maps, then choose an option below Preferred Type of Travel.