An escalator is a conveyor transport device for transporting people, consisting of a staircase whose steps move up or down on tracks that keep the surfaces of the individual steps horizontal. A moving walkway, moving sidewalk, travelator, or travellator is a slow conveyor belt that transports people horizontally or on an incline in a similar manner to an escalator. In both cases, riders can walk or stand. The walkways are often supplied in pairs, one for each direction.