How do escalators work without steps falling off?

Modern escalators use George Wheeler's design, where each step is attached to a chain via a single axle, allowing it to rotate. A second set of wheels follows a different track to control the step's angle, keeping it level on the incline and flipping it for the return journey.

What was the first escalator invented for?

The first escalator, invented by Jesse Reno in 1896, was an attraction at Coney Island called the 'continuous elevator.' It was a 25° incline conveyor belt designed as a proof of concept for future transportation.

Why is the handrail on an escalator slightly faster than the steps?

The handrail moves about 2% faster than the steps to compensate for friction wear on the drive wheel. This ensures the handrail doesn't lag significantly behind the steps over time.

Can downward escalators generate electricity?

Yes, through a process called regenerative braking. When people's weight drives the motor faster than its magnetic field, the motor acts as a generator, producing electricity that can power other devices, including upward escalators.

What caused the escalator accident in Rome in 2018?

The Rome accident was caused by a catastrophic failure of multiple safety systems due to severe neglect and deliberate sabotage of maintenance records and safety features. This included a weakened main brake and a disabled auxiliary brake.

How safe are escalators if properly maintained?

When properly maintained, escalators have enormous safety margins, engineered to handle forces far beyond normal use. Experts state that catastrophic failures are vanishingly small under correct maintenance conditions.

Key Moments

Why Do Escalator Steps Have Teeth?

Veritasium

Education4 min read23 min video

Sep 11, 2025|13,513,662 views|320,217|15,109

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Key Moments

TL;DR

Escalator safety features and their tragic failure due to human negligence.

Key Insights

Escalators evolved from early conveyor belts to modern staircases by solving the problem of step rotation and safe entry/exit.

Modern escalators incorporate multiple sophisticated safety systems, including motor resistance, brakes, and interlocking comb plates.

The Rome escalator disaster was caused not by a technological failure, but by deliberate sabotage and neglect of maintenance protocols.

Regenerative braking in downward escalators allows them to generate electricity, contributing to power efficiency and inherent safety.

The 'teeth' or grooves on escalator steps interlock with comb plates at the top and bottom, preventing items from getting trapped and allowing safe disembarkation.

Ultimately, escalator safety relies heavily on diligent human maintenance; technological safeguards are rendered useless by negligence.

THE EVOLUTION OF ESCALATOR DESIGN

The concept of moving people vertically began with Jesse Reno's "continuous elevator" in 1896, a simple metal conveyor belt acting as an attraction. This initial design, while popular, was precarious to stand on due to its steep incline. A similar device by Harrods in England also proved unnerving for passengers. Early attempts at creating moving stairs, like the "revolving stairs," presented issues with tilting steps at the top and bottom, creating treacherous transitions. These early challenges highlighted the need for a stable, flat surface for passengers while maintaining continuous motion.

WHEELER'S INNOVATION AND SEABURGGER'S COMMERCIALIZATION

George Wheeler's crucial innovation, forming the basis of modern escalators, involved attaching steps to a chain via a single axle, allowing each step to rotate. By incorporating a second set of wheels following a different track, Wheeler enabled the steps to remain level during ascent and descent, and crucially, to flip upside down and store within the structure during their return journey. Although Wheeler's patent received little attention initially, Charles Seaburger later acquired it, partnered with Otis Elevator Company, and debuted the first true commercial escalator at the 1900 Paris Exposition, which became a major attraction.

ADDRESSING SAFETY GAPS AND CONVENTIONS

Early commercial escalators, despite Seaburger's improvements, still had smooth steps that created dangerous gaps at the ends, leading to incidents where clothing and even body parts could get caught. To mitigate this, a triangular shunt was introduced, directing passengers to disembark to one side. This led to the convention of standing on the right and walking on the left to optimize flow and reduce collisions. The comb plate, with its "teeth" that interlock with the escalator steps, was a significant advancement, lifting potential snags out of harm's way and allowing for safer, forward disembarkation.

ADVANCED SAFETY FEATURES AND HANDRAIL MECHANICS

Modern escalators incorporate subtle yet vital safety features. The grooved steps and the comb plate at the ends work in unison to prevent entrapment. Furthermore, skirt brushes, added in 1982, address the pinch points along the escalator's sides. The moving handrail, a concept from Jesse Reno, operates independently via a friction wheel connected to the motor. Due to wear on this wheel, the handrail is calibrated to move slightly faster than the steps, ensuring it doesn't lag behind and remains a reliable support.

REGENERATIVE BRAKING AND POWER EFFICIENCY

Downward escalators, particularly when heavily loaded, can utilize a principle known as regenerative braking. The weight of the passengers drives the motor, which, rather than consuming power, acts as a generator. An AC induction motor, when spun faster than its magnetic field, induces electric currents that create an opposing magnetic field, acting as a brake. This excess mechanical energy is converted into electrical energy, which can be fed back into the building's power grid, often used to power upward escalators. This makes escalators remarkably power-efficient.

THE ROME DISASTER: NEGLIGENCE OVER TECHNOLOGY

The tragic 2018 Rome escalator incident, where multiple safety systems failed and the escalator plummeted, was not a result of technological deficiency but of deliberate human sabotage and systemic neglect. Investigations revealed that the main brake was significantly underperforming, approximately 37% of its specification. Critically, the auxiliary brake had been intentionally disabled with plastic straps. Furthermore, error logging systems had been turned off, preventing any record of malfunctions. Maintenance records were falsified or incomplete, indicating a pervasive pattern of negligence by contractors and transit authorities.

THE IMPORTANCE OF HUMAN RESPONSIBILITY IN MAINTENANCE

The investigation into the Rome disaster pointed to a contractor, Metro Roma, and the transit authority, ATAC, as being responsible for negligent maintenance and falsification of records across the network. It was discovered that safety devices were deliberately sabotaged to avoid shutdowns. Wiretaps revealed a callous disregard for safety, with one manager referring to potential future failures in terms of statistics. This incident underscored that while escalators are engineered with enormous safety margins, capable of supporting immense weight, their ultimate safety hinges entirely on proper and honest maintenance by humans.

ESCALATORS AS A TESTAMENT TO PROBLEM-SOLVING

Escalators, from their humble beginnings as a solution to a daily inconvenience for Jesse Reno, represent a triumph of engineering and problem-solving. Modern escalators are incredibly robust, designed to withstand forces far exceeding their operational loads. The overwhelming number of safe escalator trips worldwide annually highlights their general reliability. However, the Rome disaster serves as a stark reminder that even the most sophisticated technology requires diligent human oversight. The fundamental lesson remains that human responsibility and a duty of care are paramount in ensuring the safety of public transportation systems.

Escalator Safety and Operation Guidelines

Practical takeaways from this episode

Do This

Stand on the right side of the escalator.

Keep the left lane clear for faster walkers.

Hold onto the handrail.

Ensure the escalator is properly maintained.

Be aware of your surroundings and the steps.

Step off the escalator safely, facing forward.

Avoid This

Do not stand still in the moving lane.

Do not try to stop or tamper with safety features.

Do not allow loose clothing, shoelaces, or large items to get caught in gaps.

Do not assume an escalator is safe without proper maintenance.

Escalator Safety Features

Data extracted from this episode

Feature	Year Introduced	Primary Function
Moving Handrail	1896	Provides stability and grip for riders.
Comb Plate	Unknown (modern)	Interlocks with grooved steps to lift objects clear of gaps.
Skirt Brush	1982	Prevents objects from getting trapped in side gaps.
Triangular Shunt (early)	Post-1900	Directed riders away from dangerous gaps at the top.
Revolving Stairs (early concept)	Decades before Wheeler	Attempted to provide a flat surface, but had issues with entry/exit.
George Wheeler's Design	Post-1900	Mechanism allowing steps to remain level and flip upside down for return journey.
Regenerative Braking	Modern	Motor acts as a generator on downward escalators, producing electricity and regulating speed.

Common Questions

The 'teeth' on escalator steps are actually part of the comb plate mechanism at the top and bottom. These grooves interlock with the comb plate to lift small items out of harm's way and allow for a safe dismount.