Escalator
an elevator in the form of a moving stairway. It is the most efficient machine for handling people in large numbers when the distance to be traveled is not excessive. The passengers travel on the moving treads and a single large-size escalator will deliver more than 10,000 persons per hour. Its use is principally for department stores, railroad and subway stations, theaters, and for large manufacturing plants where great numbers of employees must be transported quickly between the entrance to the building and the upper floors. They are made reversible for operation in opposite directions during different periods of the day.