As a power-driven, continuous moving stairway designed to transport passengers up and down short vertical distances, escalators are used around the world to move pedestrian traffic in places where elevators would be impractical. Principal areas of usage include department stores, shopping malls, airports, transit systems, convention centers, hotels, and public buildings.
The benefits of escalators are many. They have the capacity to move large numbers of people, and they can be placed in the same physical space as one might install a staircase. They have no waiting interval (except during very heavy traffic), they can be used to guide people toward main exits or special exhibits, and they may be weather-proofed for outdoor use.
As recently as 2004, it was estimated that the United States had more than 30,000 escalators, and that 90 billion riders traveled on escalators each year.
Modern escalators have single-piece aluminum or steel steps that moves on a system of tracks in a continuous loop. Escalators are typically used in pairs with one going up and the other going down, however in some places - especially European stores and metro stations - there are no escalators going down, the escalators only go up. Some modern escalators have transparent side panels that reveal their gearings.
Escalators are required to have moving handrails that keep pace with the movement of the steps. The direction of movement (up or down) can be permanently the same, or be controlled by personnel according to the time of day, or automatically be controlled by whoever arrives first, whether at the bottom or at the top (the system is programmed so that the direction is not reversed while a passenger is on the escalator).