Double Decker Tour Bus - 65 Passenger. double-decker bus is a bus that has two levels or 'decks'. While double-decker long-distance coaches are in widespread use around the world, double-decker city buses are less common. Double-decker buses are popular in some cities of Europe and in parts of Asia, usually in former British colonies. Some double-deckers specialise in short sight-seeing tours for tourists for, as William Ewart Gladstone observed, "the way to see London is from the top of a 'bus".