We already provided the option to use the imperial unit system in the RoutePlanner. But now you will also see the length of the route in miles on the RouteViewer page and in the Search-results.
If you select at the top right the country USA (language English or Español), you will get to see the length in miles and height in feet.
Later on you will be able to set your unit preference in your user profile (so you don't have to select the country/language choice USA.
Picture source: (CC).