How Escalators and Moving Walks Work

An escalator seems to defy a simple question: how can a staircase move without its steps colliding or leaving gaps? The answer is that the steps are not a staircase for most of their trip. They are separate platforms on wheels, joined by a chain, riding two tracks that pull them into a stair shape on the way up and fold them flat at the ends. This page walks through those parts, covers moving walks (the flat or gently inclined cousin), summarizes safety features as public bodies and reporters describe them, and sketches the history. It is a general explanation, not guidance about any particular machine.

The step chain and the tracks

Each step is a metal platform. According to a 2024 article in USC Viterbi's Illumin magazine, the steps are linked together by a pair of step chains, and every step has two sets of wheels. The upper set rides on the chains, which are pulled by drive gears, while the lower set follows a track. Because the two wheel sets follow different paths, the angle between a step's tread and its neighbor can change as it travels.

That is the secret of the folding: the paths the wheels follow decide whether the steps stand up as stairs or lie flat like a moving floor. Illumin says the wheels let the steps protrude while moving and flatten at the landing platforms. It is easy to miss, but those flat zones are where you step on and off.

The steps return underneath. Chains and steps travel around a continuous loop, going up on top and coming back down below, out of sight inside the machine.

Truss, drive and handrail

The truss is the steel framework that spans between floors. Illumin describes it as housing the machine and supporting the tracks. A motor and drive gears pull the step chain. In the same description, a rubber handrail moves at the same speed as the steps, and the balustrade, the sidewall alongside the steps, supports it.

Matching speeds matters. A handrail that outran or lagged behind the steps would pull a rider off balance, so the two are designed to stay in step with each other. Illumin also lists reversible operation, which lets a building change direction to suit heavy traffic.

One more detail from the same article: bristles along the inside edges of the balustrade keep objects out and also warn riders whose feet drift too close to the edge. They are a small and sensible piece of design, and easy to overlook when you are just trying to get to the second floor.

Comb plates and landings

At each landing the moving steps meet the stationary floor. The comb plate bridges that join. It sits at the edge of the landing, where moving steps meet fixed floor. Illumin describes comb plates at both ends of the landing platforms as keeping foreign matter from damaging internal components.

Comb plates also figure in the stopping logic. In an NPR report about why escalators sometimes stop, Florida elevator inspector Robert Rauch said many safety micro switches (small electrical switches) throughout the unit can stop the escalator in certain circumstances, for example when something is caught in the comb plate. Richelle McCaskill-Diaz, who has worked on elevators and escalators for about 30 years, described a comb impact switch as meant to stop the escalator and keep it from moving forward when something is stuck in it. A stop that startles riders is often the machine working as designed.

Moving walks: flat and inclined

A moving walk applies the same idea to a surface that stays level, or nearly so. University researchers writing in 2017 describe moving walkways as systems for facilitating pedestrian movement on specific routes. They report that conventional walkways are limited in speed, with the authors giving 3 kilometres per hour as a comfort limit, and they discuss accelerating designs in which the surface speeds up in the middle so walkers can reach top speeds of up to 12 kilometres per hour. They sort accelerating designs into four types: in-line belts, sliding parallelograms, accelerating or decelerating rollers, and sliding pallets.

The same paper notes that some moving walkways serve hilly places, such as in Medellin, Colombia, and Perugia, Italy. That is the inclined case. Technical Safety BC, the safety regulator in British Columbia, Canada, treats inclined moving walks as a place with its own rule: carts are not allowed on them unless special permission has been granted for specially designed carts.

Flat or inclined, a walkway shares the escalator's habits. It has handrails, comb-style ends and the same sensible safeguards. If you are curious about the elevator side of vertical movement, how elevators and lifts work covers the machines that serve a different job.

Safety features, as public bodies and reporters describe them

Illumin lists several built-in features: a safety brake button under a clear plastic cover, a brake that engages when a foreign object jams the escalator, handrails with an extended balustrade, ventilation to dissipate heat, and the synchronized step and handrail speeds mentioned earlier. It also notes that ASME standardizes escalator safety protocols. Different countries and building types carry different requirements, and inspection, maintenance and regulation explained covers who checks what.

Public safety bodies mostly speak to riders. Hong Kong's Electrical and Mechanical Services Department says to hold the handrail, face forward, keep loose clothing and shoelaces away from step edges, avoid waiting in the landing area, and press the Emergency Stop button immediately in the event of an accident. Technical Safety BC adds that a stopped escalator should not be used as a stairway unless special permission and extra safety measures are in place, since its brake system may be compromised. It also says emergency braking can be sudden, and that riders who feel an unexpected stop should hold the handrail and keep their balance.

More general rider guidance, and what to do in a mishap, is in elevator, lift and escalator safety. In an emergency, use the Emergency Stop button where one is available, then call emergency services; do not try to fix a machine yourself.

A brief history

Illumin traces the escalator through a handful of patents and exhibitions. Nathan Ames received a patent for "revolving stairs" in 1859, but it was never built. In 1892 Jesse W. Reno patented an "inclined elevator," described as the first working escalator, a single belt with combed plates; it debuted at Coney Island in 1896. In 1898 Charles D. Seeberger bought the patent of George A. Wheeler, who had patented a moving stairway with flat steps, and while at the Otis Elevator Company developed the first step-type moving stairway. A Seeberger-Otis escalator won a Grand Prize and Gold Medal at the 1900 Paris Exposition, and one reached Macy's in 1902.

The article credits the modern design, from about 1922, to combining Reno's cleated steps and combed plates with Seeberger's flat steps. It also says the word "escalator" comes from the Latin scala (steps) and elevatus (rise), and that Otis trademarked the name before it became generic. The Groningen researchers place early moving walkways at the 1893 World's Columbian Exposition in Chicago and the 1900 Exposition Universelle in Paris.

Rules, inspections and enforcement vary by jurisdiction, and the local authority and qualified professionals have the final word on any real installation.

The short version

An escalator is a chain of wheeled steps on two tracks that stack into stairs on the slope and fold flat at the landings, driven by a motor with a synchronized handrail. Comb plates, switches and an emergency stop add protection, and moving walks use related ideas on a flatter path. Local rules and qualified professionals decide the requirements for any real machine.