We followed this unusual bus to a parking lot, where I was finally able to get a capture. Their site (fun to look at) http://www.portlandbarkbus.com advertises “An Adventure Program For The Active Dog In Your Life.”

“As a Bark Bus Dog your pup will most likely know the sound of our bus entering your neighborhood and will run to the nearest window, tail wagging. Time to board the bus! Your dog will greet the other Bark Bus Dogs and find his or her designated seat where a pack leader will secure them safely in their Kurgo Tru-fit Smart Harness and tether. Adventure time! The Bark Bus will pick up a few more furry friends, and then embark on an hour and a half long adventure on 60 acres in Windham, Maine. Your dog will be able to play, romp, sniff, and swim under our careful supervision.”

Best to view in "Original" because other versions resized by Pbase are decidedly unsharp.

Spreading her wings, posted earlier: