This is a double decker bus, which is very common in Hong Kong,(to be more exact, an air conditioned one, but we seldom see non-air cond’ed ones nowadays)
the smaller one is a photo of a Public Light bus, a.k.a Mini bus, is a single deck Van type vehicle with a capacity of 16. They actually exist in HK, green mini buses have fixed routes and red ones(same appearance but painting is switched from green to red) have a more free lance route type. (http://en.wikipedia.org/wiki/Public_light_bus)

I know most here cannot read Chinese characters, and this is a commercial saying “Reduced from a large bus to a mini bus”(large fonts on middle right) and the small fonts on the left says “Effective slim-bodying” and a company logo(with no name) next to it.(poor advertising since most will not be able to know what company it is) On the light bus, the Chinese words says Public Light Bus 16 seats as well.

0:)