A double-decker bus is a bus that has two storeys and is used a mean of mass transport in many parts of the world, the most iconic example being the red bus in the United Kingdom. A variant with open-top is used as sight-seeing buses for tourists. In the UK they have been favoured over articulated buses because of the shorter length of double-deckers and larger amount of seating capacity; they also may be safer to operate through the narrow streets and tight corners common in Britain.
Source: wikipedia
