That video shows a articulated/double-decker bus hybrid, a very
rare type of bus. Not many such buses exist, because while they
have very large capacities (larger than many bendy buses and
definitely larger than any double-decker), however, they combine
every disadvantage of both double-deckers and bendies (hog road
space, height restrictions, etc.). Not only that, but thanks to
their size, they usually need really large and powerful engines
(read: noisy engines) and some kind of special systems on board to
prevent all kinds of stability problems (both double-decks and
bendies themselves already have centre-of-gravity and longitudinal
stability problems, respectively). Most buses of this type are
unsuccessful, and the model shown in the video, the Neoplan N138
JumboCrusier (actually a coach), had only 10 of it built (although
an 11th similar model was also built).
Sources:
http://jumbocruiser.mysite.wanadoo-members.co.uk/
http://en.wikipedia.org/wiki/Articulated_bus
