Escalator

An escalator is a vertical transportation device in the form of a moving staircase – a conveyor which carries people between floors of a building. It consists of a motor-driven chain of individually linked steps. These steps are guided on either side by a pair of tracks which force them to remain horizontal.

Escalators are used around the world in places where elevators would be impractical. Principal areas of usage include department stores, shopping malls, airports, transit systems (railway/railroad stations), convention centers, hotels, arenas, stadiums, and public buildings.

Escalators have the capacity to move a large number of people, and they can be placed in the same physical space as 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 weatherproofed for outdoor use. A non-functioning escalator can function as a normal staircase, whereas many other conveyances become useless when they break down.

Escalators, like moving walkways, move at constant speeds of around 0.3–0.6 metres (1–2 ft) per second. The typical angle of inclination of an escalator to the horizontal is 30 degrees, and the total difference in height can be about 18 metres (60 ft) or more. Modern escalators have single-piece aluminum or stainless steel steps that move on a system of tracks in a continuous loop.

Escalators have three typical configuration options: parallel (up and down escalators side by side or separated by a distance, seen often in metro stations and multilevel motion picture theaters), crisscross (minimizes space requirements by "stacking" escalators that go in one direction, frequently used in department stores or shopping centers), and multiple parallel (two or more escalators together that travel in one direction next to one or two escalators in the same bank that travel in the other direction).

As a safety measure, escalators are required to have moving handrails that keep pace with the movement of the steps. This helps riders steady themselves, especially when stepping onto the moving stairs. Occasionally, a handrail will move at a slightly different speed from the steps, causing it to "creep" slowly forward or backward relative to the steps. The loss of synchronization between handrail and step speed can result from slippage and wear. As a result, escalators must have moving handrails that move at the same speed as the moving stairs of the escalator.

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Wikipedia