How Elevators Work

Before the safety elevator existed, buildings couldn’t be taller than five or six stories. Not for engineering reasons, you could stack stone as high as you wanted. The limit was human legs. Nobody wanted to climb ten flights of stairs. When Elisha Graves Otis demonstrated his safety brake in May 1854 at the Crystal Palace Exposition in New York City — by cutting the rope on a hoisted platform while standing on it, and not dying — he didn’t just invent a machine. He invented the modern city skyline.

The short answer

Most elevators work using a traction system: a motor at the top of the shaft winds a set of steel cables (called hoist ropes) that are attached to the elevator car on one side and a counterweight on the other. The motor doesn’t have to lift the full weight of the car; the counterweight (usually equal to the car’s weight plus half its rated capacity) does most of the balancing.

A sophisticated control system manages exactly how fast the motor moves, coordinates calls from multiple floors, and monitors a continuous stream of sensor data to keep the ride smooth and the car precisely level with each floor.

The full picture

The counterweight: the elegant solution

Without a counterweight, lifting a fully loaded elevator car from the ground floor to the 30th would require enormous energy. The motor would strain to lift the full weight of the car plus passengers on every trip up, and would need a braking system to dissipate all that energy on the way down.

The counterweight makes the system nearly balanced. A car loaded to half capacity is roughly equal to the counterweight on the other end. Going up with a half-loaded car takes almost no net energy; the motor just maintains control of the movement. Going down with a lighter car, the heavier counterweight does the work.

Modern elevators even recover energy from this process. When the system is moving in a direction where gravity helps (a heavy counterweight descending), the motor acts as a generator and feeds electricity back into the building’s power supply. This regenerative braking can reduce energy consumption by up to 30–35%, according to Mitsubishi Elevator and industry studies — a meaningful figure given that elevators typically account for 2–5% of a building’s total energy use.

The cables: more redundancy than you think

An elevator doesn’t hang by one cable. It hangs by six to eight steel cables (depending on the size), each individually strong enough to hold the car and its maximum load with a safety margin several times over.

The cables are made of hundreds of thin steel wires twisted together, a structure that distributes stress and prevents a single weak point from causing failure. The wires are regularly inspected, and cable tension is precisely balanced across all cables so no single one bears disproportionate load.

But here’s the key: even if every cable snapped simultaneously (an essentially impossible scenario, but the engineers planned for it), the car would not fall freely.

The safety brake: Otis’s original innovation

Elisha Graves Otis didn’t invent the elevator. He invented the safety brake — patented in 1861, conceived around 1852 — which is what made tall buildings possible.

Otis designed a spring-loaded ratchet mechanism attached to the car. If the cable suddenly goes slack (as it would in a free fall), the springs force the ratchet into a guide rail running along the side of the shaft, stopping the car immediately. He demonstrated this publicly by cutting the cable on a platform he was standing on, at the Crystal Palace Exposition in New York in 1854. The car dropped an inch and held. The Otis Elevator Company, founded by Otis in 1853, still manufactures elevators today as one of the world’s largest elevator companies.

Modern safety gear works on the same principle. Speed governors constantly monitor how fast the car is moving. If the speed exceeds a threshold (a car falling would accelerate beyond normal operating speed), the governor triggers safety clamps that grip the guide rails and stop the car within a short distance. The stopping is firm but survivable.

The control system: coordinating a building

In a multi-elevator building, naive scheduling (send the nearest elevator to every call) quickly becomes inefficient. Modern elevator control systems use sophisticated algorithms to minimize average wait time across all floors.

These systems continuously track every car’s position, direction, and load. They predict where demand will come from based on time of day (office buildings have predictable rush patterns: down in the morning, up after lunch, down in the late afternoon). Some newer systems use destination dispatch: instead of pressing up or down in the hallway, you enter your destination floor, and the system groups passengers going to nearby floors into the same car, reducing total trips.

The precision of positioning is also impressive. An elevator stops within a few millimeters of the floor level, consistently, across millions of cycles. This is managed by a combination of floor sensors and fine motor control, ensuring no tripping hazard at the threshold.

Hydraulic elevators: the alternative

In low-rise buildings (typically under five stories), hydraulic elevators are common. Instead of cables and a counterweight, a piston underneath the car pushes it up using pressurized hydraulic fluid. A pump forces fluid into the cylinder to raise the car; releasing the fluid lets the car descend under gravity.

Hydraulics are simpler and cheaper to install. Their limitation: the piston must extend as tall as the building, and they’re less energy-efficient for taller applications. They also require a pump room and fluid reservoir below the shaft.

The future of vertical transport: ropeless elevators

For 170 years, the cable-and-counterweight model defined how elevators work. Now a fundamentally different approach is being commercialized.

Magnetic levitation elevators, most notably TK Elevator’s MULTI system (formerly Thyssenkrupp Elevator), use linear induction motors instead of cables. The cars are propelled by electromagnetic force and can move both vertically and horizontally within a building. Multiple cars can operate in the same shaft simultaneously, like a circular elevator system, because nothing physically connects them to a fixed cable.

This isn’t a gimmick. The cable model has a hidden constraint: the heavier the cable, the less of the cable’s weight budget can be used for the actual load. Elevators in supertall buildings, the 600-meter towers going up in Dubai, China, and Saudi Arabia, require cables so heavy that a significant portion of the system’s capacity is consumed just moving the cable itself. Beyond certain heights, traditional cable elevators become impractical regardless of motor power. Ropeless designs eliminate this constraint.

The first MULTI installation was inaugurated in Berlin’s East Side Tower, planned for completion in the early 2020s (the prototype was demonstrated at TK Elevator’s 246-metre test tower in Rottweil, Germany). The cost is still far higher than conventional systems, but as supertall buildings proliferate, the economics may shift. The city-in-a-building concept, kilometer-tall structures housing thousands of people, depends on this kind of innovation the same way 19th-century cities depended on Otis’s original brake.

Common misconceptions

If one cable snaps, the elevator will fall. Elevators use multiple cables, each strong enough to hold the car alone. Even if all cables failed, the safety brake would engage automatically.

Elevators can free-fall to the bottom. The safety brake (originally invented by Elisha Graves Otis) clamps onto guide rails if the car accelerates beyond normal speed. Multiple independent safety systems prevent free fall.

You’re safer taking the stairs during an earthquake. Modern elevators are built to strict safety codes and are inspected regularly. The more dangerous choice is typically the stairwell.

Hydraulic elevators are more dangerous than traction elevators. Both are extremely safe. Hydraulic elevators are simply a different technology commonly used in low-rise buildings, with their own redundant safety features.

Why it matters

Modern cities exist because of elevators. Without them, buildings couldn’t practically be taller than five or six stories (the limit of comfortable stair climbing). The entire model of vertical urban density, which allows millions of people to live and work within walkable distance of each other, depends on reliable vertical transportation.

The engineering behind elevators is a masterclass in layered safety: multiple cables, each sufficient alone; a governor that monitors speed; safety clamps that engage automatically; and software that manages the whole system. The result is that modern elevators are statistically among the safest transportation systems in existence. You are far more at risk walking to the elevator than riding in it.