The core of an escalator is a pair of chains looped around two sets of gears. An electric motor turns the drive gears at the top, rotating the chain loops. A typical escalator uses a 100‑horsepower motor. The motor and chain system are housed inside a truss—a metal structure spanning the space between two floors.

Unlike a conveyor belt that moves a flat surface, the chain loops move a series of steps. The steps remain level as the chains move, and at the top and bottom they collapse onto one another, forming a flat platform that eases boarding and alighting.

Each step contains two sets of wheels that run along separate tracks. The upper wheels, located near the step’s top, are driven by the rotating chains and the top drive gear. The lower wheels glide along a second track, following the motion of the upper set.

The track spacing is engineered so every step stays level. At the top and bottom, the tracks become horizontal, flattening the stairway. Each step has interlocking grooves that mate with the steps ahead and behind during this flattening.

The electric motor also powers the handrails. A handrail is a rubber conveyor belt looped around a series of wheels, moving at exactly the same speed as the steps to provide riders with stability.

Escalators are not designed to lift people many stories like elevators, but they excel at short‑distance transfers because of their high loading rate. While an elevator must wait for its capacity to fill before it can depart, an escalator accepts a new passenger immediately after one boards.

For more technical details, consult industry standards and engineering references.