plus-15s noun (pedestrian) overpasses connecting buildings in Calgary, Alberta CANADA
It’s a city that is growing rapidly, with new buildings and “plus-15s” springing up all the time. “Plus-l5s” [is a term] referring to their height above the street--though given the weather they should probably be called minus-15s. — MontrealGazette, p. F2, 29 May 2002