Tap a claim to open the verdict. Everything here links to a source at the bottom.

The one that’s actually useful

If an elevator stops between floors: stay inside, press the alarm or call button, and wait for the voice. Don’t pry the doors and don’t climb out. The car is the safest place in the building, and the people coming to get you do this all the time.

Sources

1. computer.rip: the door close button (quotes and corrects the 2016 New York Times story)
2. People: Betty Lou Oliver and the longest elevator fall survived
3. Brouss Elevators: what to do if you're stuck in an elevator
4. Reader's Digest: why buildings skip the 13th floor
5. 6sigma: on queueing and elevator mirrors
6. HistoryLink: Muzak
7. Statista: elevators and escalators in operation worldwide

The fastest elevator on record climbs 440 meters in about 42 seconds, then comes back down at half speed, on purpose.

The short version

• The Guinness record belongs to a Hitachi elevator in the Guangzhou CTF Finance Centre: 21 m/s (47 mph) going up, certified in 2019.
• Before that, Mitsubishi Electric’s Shanghai Tower cars held the title at 20.5 m/s.
• The CTF record car goes down at 10 m/s. Hitachi also engineered cabin pressure control against the ear-popping.
• TWIN puts two independent cars in one shaft. MULTI throws out the rope entirely and uses linear motors, so cabins can move sideways.
• UltraRope swaps steel for carbon fiber so a single elevator run can approach a kilometer.
• And a few hundred paternosters, open cabins on a loop that never stop, still run in Germany.

The speed war

Hitachi’s CTF elevator goes from the ground floor to the hotel lobby on the 95th floor, 440 meters, in about 42 seconds. Hitachi’s spec sheet lists its rated speed as 1,260 m/min going up and 600 m/min going down. To keep that comfortable, the car has a capsule-shaped body borrowed from high-speed-rail design, active guides that damp vibration, and pressure control to fight blocked ears. The brakes use special heat-resistant friction material, because stopping a car from 47 mph turns a lot of motion into heat.

Mitsubishi’s Shanghai Tower cars set the Guinness record at 20.5 m/s in 2016, one of several elevator records the tower collected that year. Hitachi’s certificate came in 2019. If you’ve seen “world’s fastest elevator” attached to both buildings, that’s why.

Two cars, one shaft

TK Elevator’s TWIN runs two completely independent cars in the same shaft, each with its own motor, controller, and safeties. The upper car serves upper floors, the lower car serves lower ones, and the dispatch system has one extra hard rule: they never meet. If they get too close, drives cut out and the safety gear can engage. TK says the payoff is more capacity from the same building footprint, plus parking one car when traffic is light.

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MULTI: no rope, and it goes sideways

MULTI is the elevator from science fiction. There’s no rope. Each cabin rides on linear motors, the same basic idea as a maglev train, which means several cabins can share a loop of shafts, and a rotating section of rail can send a cabin horizontally into the next shaft. TK Elevator installed it in 2017 in its elevator test tower in Rottweil, Germany.

The honest status check: as of 2024, Wikipedia’s entry lists no MULTI installations outside test sites, so it’s still a test-tower story, not something you’ll ride at the office. Ropeless doesn’t mean brakeless either. The design literature leans hard on layered braking and dense sensors.

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Carbon-fiber rope

In a really tall building, the steel rope itself becomes the problem. At some point most of what the motor lifts is rope, not people. That’s why supertall towers use sky lobbies, where you change elevators partway up. KONE’s UltraRope, launched in 2013, replaces steel with a carbon-fiber core. KONE says it’s a small fraction of the weight of equivalent steel rope, and that it makes single elevator runs of around a kilometer practical, roughly double the old limit. It was chosen for the planned Jeddah Tower in Saudi Arabia, a kilometer-class building designed around 58 elevators and all-digital destination dispatch.

The elevator that never stops

A paternoster is a chain of open cabins going up one side and down the other in a continuous loop, about as fast as a slow walk. There are no doors and no buttons. You step on, and you step off at your floor. West Germany banned new ones in 1974, but Germans love the survivors. A few hundred still run there, with more in the UK and Central Europe, and preservation campaigns have fought off attempts to shut them down.

Sources

1. Hitachi: Guangzhou CTF elevator wins Guinness World Records title as the world's fastest (2019)
2. Mitsubishi Electric: Shanghai Tower Guinness World Records (2016, PDF)
3. Otis: SkyRise brochure (Burj Khalifa double-decks at 10 m/s, PDF)
4. Wikipedia: Usain Bolt (top speed)
5. Wikipedia: TK Elevator MULTI
6. ENR: UltraRope can double the maximum run to 1 kilometer, says KONE
7. Elevator World: the elevator designs of Jeddah Tower
8. 99% Invisible: paternoster lifts
9. Nationwide Lifts: Germans fight to keep paternoster elevators

Find the oldest phone line in a modern office building and there's a decent chance it's the one in the elevator.

The short version

• Elevator codes require a two-way emergency communication device in every car. Press the button and you have to reach a real person who can send help.
• For decades, that meant an analog phone on a copper POTS line, usually one line per elevator bank, auto-dialing a monitoring company.
• Carriers are retiring copper. AT&T has said it plans to get out of most traditional landline service by 2029.
• The replacements are cellular communicators (often LTE, with battery backup and the antenna outside the steel shaft) or IP-based systems.
• The 2019 edition of the elevator code added a text or video requirement, so riders who are deaf, hard of hearing, or can’t speak can communicate too.

What the code actually asks for

In North America, ASME A17.1 section 2.27 covers emergency communication. The basics, in plain English:

• A button in the car that starts a two-way voice call, with no handset to pick up and nothing to dial.
• The call goes to authorized personnel who can respond around the clock, typically a monitoring service.
• A visual signal in the car that lights up when the call is acknowledged, so a rider who can’t hear knows help was reached.
• Since A17.1-2019, per the National Elevator Industry Inc., the code spells out requirements aimed at riders who are deaf, hard of hearing, or speech impaired, which in practice means a two-way text or video display in the car for buildings that fall under that edition.

The ADA standards add that the system can’t rely on voice alone.

Why the copper matters

A POTS line is a very simple, very reliable thing. The phone company feeds it power from the central office, so it keeps working when the building’s power is out. It has a dial tone you can test, and old elevator phones were designed around exactly that behavior.

That copper is going away. In late 2024 AT&T said it planned to eliminate traditional landline service in 20 of its 21 states by 2029, and other carriers are shrinking their copper networks too. According to emergency-phone vendor Kings III, an FCC change that took effect in March 2026 means carriers no longer need the agency’s approval before retiring copper, just 90 days’ notice to customers. So building owners are facing a forced upgrade on one of the most safety-critical phone lines they have.

What’s replacing it

• Cellular communicators. A box that presents a phone-line interface to the elevator phone and connects over LTE instead. Since steel and concrete shafts kill cell signal, the antenna usually goes on top of the car, in the machine room, or outside the hoistway, and the unit carries a battery because it no longer gets power from the phone company. Many are sold as “dual path,” with a second connection for backup.
• VoIP / IP systems. The elevator phone rides the building network. That works, but now the phone depends on the building’s power, switches, and internet, so battery backup and network design matter a lot more.
• Car displays. To meet the newer text and video rules, the car gets a small screen, and the monitoring center can type or show video back.

Sources

1. NEII: elevator emergency communications and A17.1-2019 requirement 2.27.1
2. UpCodes: ASME A17.1 Section 2.27
3. Kings III: what the latest elevator code says about emergency phones
4. USA Today: AT&T to eliminate most traditional landline service by 2029
5. Kings III: POTS emergency phone replacement
6. DataRemote: elevator emergency communication
7. U.S. Access Board: ADA Accessibility Standards (section 407, elevators)

Somewhere there's a dashboard that knew your office elevator's door was getting sticky before anyone in the building noticed.

The short version

• All the big makers sell connected service: an edge gateway reads the controller and sensors and streams data to the maker’s cloud.
• The pitch is predictive maintenance: catch a door that’s slowing down or a brake switch that’s drifting before it strands someone.
• Elevators also expose APIs now, so delivery robots and building apps can call cars.
• The core safety systems still work locally. If the cloud goes down, the car should lose features, not safety.
• We couldn’t find a publicly documented ransomware attack that stopped passenger elevators. Security folks still treat these gateways as operational technology that belongs on its own segmented network.

The big four’s platforms

• Otis ONE. Launched in 2019 as Otis’s IoT service platform. It combines decades of remote elevator monitoring with cloud analytics and machine learning, and gives building owners a live view of their equipment. Otis has talked publicly about a cloud data lake taking in data from controllers, drives, and doors across its fleet.
• KONE 24/7 Connected Services. Built with IBM’s Watson IoT platform after a 2016 partnership. KONE and IBM material describes monitoring hundreds of parameters per unit across a very large connected fleet.
• Schindler Ahead. An on-site gateway called the Ahead Cube connects the elevator, with a technical operations center and apps on top. Schindler says it can push updates to the gateway’s apps over the air, which is a different thing from updating the safety-rated controller firmware.
• TK Elevator MAX. A cloud predictive-maintenance platform running on Microsoft Azure. TK Elevator cites well over 100,000 connected units and claims large cuts in downtime and breakdowns. Those are the company’s own numbers.

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What the sensors actually watch

Past the controller’s own fault codes, connected elevators track things like door cycles and door timing (doors open and close hundreds of times a day, so they wear fast), trip counts, motor and bearing temperature, machine vibration, brake switch timing, and in some systems rope or belt condition. A door that takes a little longer to close each week is exactly the kind of drift a model can flag before it turns into a stuck car on a Friday night.

Robots take the elevator

Once an elevator has an API, it doesn’t care whether a human or a robot is calling it. Otis markets robot integration through its dispatch system, and Schindler publishes a REST-style integration API that supports robots and credentials like QR codes, faces, and phones. Hotel and hospital delivery robots that ride elevators by themselves already work this way. Some of them just push the buttons with an arm.

The honest security picture

Here’s what we could and couldn’t find:

• Safety stays local. The safety chain, governor, and brakes don’t depend on the network (Floor 2). A cloud outage should degrade monitoring and fancy dispatch features, not make a car unsafe.
• Lots of the installed base is offline, or reaches its maker only through a modem or VPN. We didn’t find a reliable public count of how many US elevators are connected.
• No confirmed public case of ransomware shutting down passenger elevators at a major maker turned up. The closest public material is training and research. The DFRWS 2023 forensics challenge, “Troubled Elevator,” was built around a malfunctioning bank elevator controller with network captures and memory dumps to analyze.
• The advice from the industry is the same as for any operational technology: authenticate remote sessions, keep the elevator gateway off the general office network, and never expose controller engineering ports to the internet.

Sources

1. PR Newswire: Otis launches Otis ONE (2019)
2. Otis: Otis ONE
3. Altoros: KONE and IBM Watson IoT
4. Schindler: digital services and Ahead
5. TK Elevator: MAX
6. Schindler: BuilT-In integration API (PDF)
7. DFRWS 2023 forensic challenge: Troubled Elevator
8. KEB America: remote monitoring for elevators

The dispatch AI gets the headlines. Most of the code is a very careful answer to one question: what mode am I in right now, and what am I allowed to do in it?

The short version

• A modern controller is a state machine. Normal service is just one state out of many.
• Fire Phase I recalls every car to a safe floor. Fire Phase II hands one car to a firefighter with a key, and the controls change behavior.
• Inspection mode lets mechanics ride the car top at a crawl. Earthquake and emergency power modes decide who moves and when.
• The firefighter’s key was standardized in many places so any fire crew could use any building’s elevators. Security researchers have pointed out the obvious downside.
• The service tools that read fault codes and change parameters are often proprietary, which has turned elevators into a right-to-repair fight.

Fire service, up close

Fire codes treat elevators as something to take out of public use during a fire, not an escape route. Shafts can fill with smoke, power can fail, and water from sprinklers and hoses gets everywhere. So:

• Phase I (recall). Triggered by a smoke detector in a lobby, machine room, or shaft, or by a key switch at the fire recall floor. Cars cancel every call, head for the designated floor (or an alternate floor if the smoke is at the main floor), open, and park. The light-curtain door sensors are typically switched off in this mode, because smoke can block the beam and hold the door open forever.
• Phase II (firefighter operation). A firefighter gets in and turns the in-car key. Now the car answers only its own buttons. The doors open only while the firefighter holds the button, and if they let go early the doors close again, so a firefighter can peek at a smoky floor and back out. Here, finally, the door close button does exactly what it says.

Some newer high-rises go further with occupant evacuation operation, where protected elevators help empty the building under tightly controlled conditions. Codes and local adoption vary, so it’s not everywhere.

The key problem

For firefighters to use Phase II, they need a key that works. In many jurisdictions that means a standardized fire service key, so a crew doesn’t need a ring of hundreds. Security researchers Deviant Ollam and Howard Payne spent a DEF CON 22 talk walking through elevator terminology, modes, and controls, and the tension is easy to see. A key every firefighter can carry is a key other people can get too. We’re not going to describe the key. The public talk is the right place to go for the security side.

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Tech tools and the right-to-repair fight

On older equipment, a skilled mechanic could fix almost anything with a meter and a wiring diagram. On a lot of newer proprietary controllers, you can’t even read the fault log without the manufacturer’s service tool. Depending on the brand, that’s a handheld unit, a laptop app, or a key-card, and independent elevator companies say they either can’t get one or can only lease one on the manufacturer’s terms.

Elevator World and independent contractors describe the same pattern as the car and tractor right-to-repair fights. Building owners who want to switch maintenance companies can find the new company locked out of their own equipment. The counter-move is open-architecture controllers from independent makers, sold on the promise that any licensed mechanic can service them with published tools. That’s also why “modernization” jobs so often replace the whole controller.

Sources

1. UpCodes: ASME A17.1 Section 2.27, emergency operation and signaling devices
2. DEF CON 22: Ollam & Payne, Elevator Hacking (slides, PDF)
3. Elevator World: The Right to Repair
4. Elevator Blueprint: OEM vs. independent elevator companies

Pressing "up" doesn't call an elevator. It files a request with a scheduler that's juggling every car in the bank and guessing what everyone else is about to do.

The short version

• The classic rule is collective control: a car answers every call in its direction of travel, then turns around. If you’ve studied disk scheduling, it’s basically the SCAN algorithm.
• Banks of cars add a group supervisor that assigns each hall call to the car with the best estimated arrival time, and switches strategy for morning rush, lunch, and evening.
• Destination dispatch asks for your floor in the lobby, then groups people going to the same floors into the same car. Schindler invented the first practical one, the Miconic 10, in 1990 and introduced it in 1992.
• Modern makers advertise fuzzy logic, neural-network traffic prediction, genetic algorithms, and machine-learning tuning. Some of that is well documented, and some of it is brochure language.
• Below, you can race the two approaches yourself.

Classic: up, down, and hope

With plain up/down buttons, the system knows that you want to go up, but not where. So a car stops for you, everyone piles in, and then everyone presses a different floor. In a morning rush, a car leaving the lobby with 12 people can easily end up stopping at 8 or 9 floors, and its round trip gets long. The next person waiting in the lobby pays for every one of those stops.

Destination dispatch: tell it where first

Destination dispatch moves the floor buttons into the lobby. You type 14 on a kiosk (or badge in, or tap your phone), and the screen tells you which car to take. The computer now knows every rider’s destination before they board, so it can send the three people going to 14 and the two going to 15 together, and put the people going to 6 in a different car.

Each car makes fewer stops, so it gets back to the lobby sooner, and waits get shorter. That’s why many of these buildings have no floor buttons inside the car at all. It’s also why you shouldn’t follow your friend into Car B if the kiosk told you Car D. Car B doesn’t know you exist.

What the big makers say they’re doing

Group control algorithms are proprietary, so what we have is what the manufacturers choose to publish. Treat the fancier claims as marketing unless there’s detail behind them.

• Mitsubishi Electric ΣAI-2200C. The best-documented. The brochure describes fuzzy logic and expert-system rules, neural-network traffic prediction, a “Dynamic Rule-set Optimizer” that simulates competing strategies every few minutes and picks the winner, “psychological” waiting-time scoring, and an energy-saving mode that prefers the cheaper move (like a heavy car going down) when several cars could arrive at about the same time.
• Otis Compass 360 / Compass Infinity. Destination management with “SmartGrouping.” Otis says Compass Infinity uses machine learning to tune the hundreds of dispatch parameters that would otherwise be set by hand and go stale as a building’s traffic changes.
• KONE Destination. KONE’s brochure language lists traffic forecasting, fuzzy logic, and genetic algorithms. That’s a vendor claim. Nobody outside KONE has published the internals.
• Schindler PORT. The descendant of the 1992 Miconic 10. It adds identity: your badge can carry your default floor, access rights, and accessibility needs, like extra door time.
• TK Elevator TWIN. Two cars in one shaft, so the scheduler also has to keep them from ever meeting. More on Floor 8.

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The access-control twist

Once the elevator knows who you are, it becomes part of building security. Access control integrator AMAG describes two patterns. In one, the elevator asks the badge system, in real time, “may this person go to floor 12?” In the other, the cardholder database is copied into the elevator system, which decides locally. Either way, your floor choice is now tied to your badge. That’s handy for tenants, and it’s one more system for the building’s IT people to think about.

Sources

1. Wikipedia: Destination dispatch
2. Schindler: Miconic 10 (1992) and PORT
3. Mitsubishi Electric: ΣAI-2200C group control brochure (PDF)
4. Otis: Compass 360
5. KONE: Destination brochure (PDF)
6. Schindler: PORT destination control
7. AMAG: destination dispatch and access control white paper (PDF)
8. Elevator Saga: documentation

For most of the 20th century, the elevator's program was a wiring diagram. You could hear it think.

The short version

• Early electric elevators had a human operator running a lever. Automation didn’t take over until the 1940s and ’50s.
• For about 90 years, smooth speed control came from Ward Leonard motor-generator sets: a motor spinning a DC generator whose output drove the hoist motor.
• Logic lived in walls of relays. Floor selectors, timers, and interlocks were all mechanical and electrical, and techs debugged them by ear.
• Microprocessor controllers arrived in the 1980s, and variable-frequency drives replaced the motor-generators.
• A modern elevator is a small network: car controllers, a group supervisor, a drive, door operators, and fixtures, talking over CAN bus, serial links, and Ethernet.

When you could hear it think

Walk into an old machine room and the controller is a steel cabinet, or a whole wall, of relays. Each floor has relays that latch when you press its button. A mechanical floor selector, basically a scale model of the shaft driven by the machine, tracks where the car is and trips contacts to slow it down at the right place. Timers are dashpots and thermal relays. When a call gets answered, you hear a cascade of clacks.

Troubleshooting meant a meter, the wiring diagram, and a good ear. The upside: everything was visible, and a skilled mechanic could fix almost anything with parts off the shelf.

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The modern stack

Today the same job is split into layers, and each layer is its own computer.

• Car controller. One per car. Runs the doors, leveling, direction, special modes (Floor 5), fault handling, and the speed profile sent to the drive.
• Group supervisor. Owns the bank. Decides which car answers which call, parks idle cars, and switches strategies for morning rush, lunch, and evening (Floor 4).
• Drive. A variable-voltage, variable-frequency (VVVF) inverter that synthesizes three-phase power for the motor. It follows jerk-limited “S-curve” speed profiles, which is why a good elevator starts and stops without that stomach lurch. An encoder closes the speed loop.
• Position. Absolute encoders and landing-system magnets or tape in the shaft. After installation, the car does a slow learning trip to map every floor height into memory.
• Buses. CAN bus, RS-485, and proprietary serial links to car panels, hall fixtures, door operators, and load-weighing sensors. Ethernet between cars and the group computer.

Open-architecture controller makers publish enough to show how this is organized. MCE’s Motion series, for example, splits the car into operation control, motion control, and power control boards, with CAN ports where a handheld tool plugs in and Ethernet for a PC monitoring app.

What the technician sees

On a modern controller, the “machine room” is a small screen or a handheld tool. Typical menus include live car status (position, speed, direction, door state, safety chain inputs), a fault log with codes and timestamps, drive parameters (contract speed, acceleration, jerk, encoder counts, motor nameplate), hoistway learning, mode overrides for inspection and testing, raw I/O monitoring, and group screens showing every hall call and car assignment.

Some tools are physical keys to the kingdom. This video shows a technician restoring a Mitsubishi controller board’s program with the manufacturer’s service card, a rare look at OEM maintenance software.

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Who gets those tools is a live fight. More on that on Floor 5.

Sources

1. Wikipedia: Ward Leonard control
2. Wikipedia: Elevator (history, Siemens 1880)
3. Wikipedia: Elevator Strikes (New York, 1945)
4. KONE: MonoSpace and EcoDisc, 1996
5. KEB America: regenerative drives for elevators
6. Nidec Elevator / MCE: Motion controller documentation

The elevator wasn't the breakthrough. People had hoists for centuries. The breakthrough was a brake that works when everything else has already failed.

The short version

• In 1854, Elisha Otis stood on a platform in New York’s Crystal Palace, had the hoist rope cut with an axe, and a spring-loaded catch grabbed the notched guide rails. He dropped a few inches.
• Today’s version is a chain: an overspeed governor notices the car going too fast, cuts power, then pulls a lever that jams safety wedges against the rails.
• The motor brake is spring-applied and electrically released. Cut the power and it clamps by itself.
• Doors are part of the safety loop. The car can’t run with a landing door unlocked, and a landing door can’t be opened unless the car is there.
• Newer codes add unintended car movement protection (UCMP): if the car creeps away from a floor with the doors open, a separate brake has to stop it within about four feet.

The stunt that sold skyscrapers

Otis’s safety wasn’t an instant hit. Elevator World’s history notes he sold only a handful of elevators in the year after the Crystal Palace show, and the first safety elevator built to carry passengers didn’t go into service until 1857, in the E.V. Haughwout Building in Manhattan. But the idea stuck, and it’s still the foundation: assume the rope is gone, and stop the car anyway.

Why the software doesn’t get a vote

Modern controllers are full of computers, but the core safety devices are designed to fail safe without them. The governor is a spinning wheel with flyweights. The safeties are steel wedges. The machine brake is a spring held open by an electromagnet, so a power cut applies the brake.

Electrically, all the critical switches (door locks, the governor switch, pit stop switches, final limit switches at the top and bottom of the shaft) sit in one long series loop called the safety chain. Open any one of them and power to the motor and brake drops. The software can watch the chain, and newer electronic safety boards are certified to strict functional-safety levels, but it can’t wish a broken chain closed.

The door problem and UCMP

For decades the scariest accidents weren’t falls. They were cars that moved with the doors open, from a brake that slipped or a control fault, catching someone half in and half out. Codes on both sides of the Atlantic now require unintended car movement protection. ASME A17.1 in North America and EN 81-20 in Europe both call for detecting that movement and stopping the car within a short distance, about 1.2 meters (48 inches) in the North American rule, using a brake that doesn’t depend on the thing that just failed.

Many older traction elevators are being retrofitted with rope grippers or dual brakes to meet this, on deadlines set by local code.

The one famous fall

Real free falls are so rare that the most famous one needed a B-25 bomber. On July 28, 1945, an Army plane lost in fog hit the Empire State Building. Debris cut the cables on the elevator that operator Betty Lou Oliver was in, and it fell about 75 stories. She survived, and Guinness still lists it as the longest survived elevator fall. Accounts credit the pile of coiled cable in the pit and the air cushion in the shaft for slowing the car.

Sources

1. Elevator World: Elisha Otis at the Crystal Palace, Part 2
2. National Inventors Hall of Fame: Elisha Graves Otis
3. FIRGELLI: how elevator safety gear works
4. HydraSafe: understanding the code update on unintended car motion
5. Elevator World: compatibility of systems and subsystems in UCMP
6. ASME A17.1-2022 table of contents
7. People: Betty Lou Oliver still holds the record for the longest elevator fall survived
8. Brouss Elevators: what to do if you're stuck (elevators aren't airtight)

The motor in a traction elevator isn't hauling your whole weight up the building. It's tipping a balance that's already almost level.

The short version

• Most mid- and high-rise elevators are traction elevators: steel ropes or flat belts run over a grooved wheel (the sheave), with the car on one side and a counterweight on the other.
• The counterweight usually weighs about as much as the empty car plus 40 to 50% of its rated load. So the motor only moves the difference.
• Short buildings often use hydraulic elevators instead: a pump pushes oil into a cylinder and a piston shoves the car up. Cheap, simple, slow.
• Since 1996, many traction elevators have had no machine room at all. A flat motor bolted inside the shaft does the work.
• Fun consequence of the seesaw: an empty car going up is actually the light side winning. The motor has to hold it back, and a modern drive turns that braking into electricity.

Traction: friction does the lifting

Nothing is tied to the motor. The ropes just drape over the sheave, and friction in the grooves grips them. Turn the sheave one way and the car rises while the counterweight falls. Turn it the other way and they swap. That’s where the name “traction” comes from.

The counterweight is the whole trick. With it sized at roughly an empty car plus 40 to 50% of capacity, a half-full car is almost perfectly balanced, and the motor barely works. The worst cases are the extremes. A packed car going up means the motor lifts the difference. An empty car going up means the counterweight is heavier and wants to fall, so the motor acts as a brake.

In old buildings that braking energy went into big resistor banks and became heat, which is one reason old machine rooms were so hot. Modern regenerative drives push it back into the building’s electrical system instead.

Tall buildings add two more details. Roping ratios like 2:1 loop the rope through pulleys on the car, trading speed for pulling force, like a block and tackle. And compensation chains hang under the car and counterweight so the weight of the ropes themselves doesn’t pile up on one side as the car travels.

Hydraulic: the car on a stick

For two to six stops, a lot of buildings skip all that and use a hydraulic elevator. A pump pushes oil into a cylinder, a piston (the “jack”) pushes the car up, and a valve lets the oil back out to lower it. Gravity does the downhill work. Classic installs bury the cylinder in a hole under the pit. “Holeless” versions stand the jacks up beside the car.

They’re cheap and simple, but slow (roughly walking speed to jogging speed), and the pump motor works hard on every up-trip, since there’s no counterweight helping.

Geared, gearless, and the machine room that disappeared

Older traction elevators used a geared machine: a fast motor turning a worm gear that turned the sheave. Rugged, but it wears, leaks oil, and loses energy in the gearbox.

Gearless machines bolt the sheave straight to a big slow motor. Smoother, faster, and the standard for high-rise work.

Then in 1996 KONE shipped the MonoSpace, the first machine-room-less (MRL) elevator, powered by a flat, disc-shaped gearless motor called the EcoDisc. KONE says the idea came to one of its engineers, Harri Hakala, while jogging. The motor got thin enough to mount on the guide rails inside the shaft, and the penthouse full of iron went away. Every major maker followed.

Otis went a different direction with Gen2: instead of round steel ropes, it uses flat polyurethane-coated steel belts. They bend around a much smaller sheave, so the machine can shrink too, and there’s no metal-on-metal contact to grease.

Sources

1. Wikipedia: Elevator (traction design, counterweight sizing, hydraulic types)
2. KONE: Making room for more since 1996 (MonoSpace, EcoDisc, the jogging idea)
3. Otis: Gen2 Premier (coated steel belts)
4. TK Elevator: conventional traction vs. machine-room-less
5. KEB America: regenerative drives for elevator applications