Lesson 6 of 8How lifts work
Lift safety systems.
A lift has several independent systems whose only job is to stop it safely when something goes wrong. Here is what each one protects against, and what happens, step by step, if a car goes too fast.
Layers of protection.
No single device keeps a lift safe. Instead, several independent systems each protect against a different kind of failure, so that if one fails another is still there.
| If… | What protects against it |
|---|---|
| the car stops at a floor or the power fails | The machine brake holds the car |
| the car goes down too fast | The overspeed governor and the safety gear |
| the car goes up too fast | Ascending car overspeed protection |
| the car moves away from a floor with the doors open | Unintended car movement protection, on lifts built to newer standards |
| the car or counterweight travels past the end floors | Final limit switches, then the buffers in the pit |
| a landing door is opened when the car is not there | The landing door interlocks |
| any safety switch opens | The safety circuit cuts power to the machine and the brake applies |
The most important of these are treated in law as safety components, which have to be certified before they are fitted to a lift.
What happens if a car goes too fast.
Step through the sequence below. It shows a car travelling down faster than it should, and the two stages of protection the governor provides.
Normal running
The overspeed governor is a pulley driven by its own steel rope. The rope runs from the governor down to a tension pulley in the pit and is fixed to the car, so the governor turns at a speed that matches the car’s speed.
The governor detects overspeed
If the car goes faster than it should, the governor’s switch opens. The switch is part of the safety circuit, so opening it cuts power to the machine.
The machine stops and the brake applies
With the power cut, the brake applies. In most cases, such as a drive fault, this alone brings the car to a stop.
The governor grips its rope
If the car keeps accelerating, for example because the brake or the suspension has failed, it reaches the governor’s tripping speed. Jaws or a ratchet inside the governor then stop and grip the governor rope.
The rope pulls the safety gear linkage
The car is still moving but its governor rope is now held, so the rope pulls a linkage on the car frame. The linkage lifts the safety gear wedges or rollers into contact with the guide rails.
The safety gear stops the car
The safety gear grips the guide rails and brings the car to a stop, independently of the ropes, machine and brake. A switch keeps the lift out of service until a competent engineer has found the cause, released the safety gear by raising the car and checked the lift.
The law
The Lifts Regulations 2016 require lifts to have an overspeed limitation device and a means of preventing free fall that works independently of the suspension, and require buffers between the bottom of the shaft and the floor of the car.
The overspeed governor.
The governor is usually at the top of the shaft or in the machine room, with its tension pulley in the pit. It works in two stages. The first is electrical: its switch opens the safety circuit, which stops the machine. The second is mechanical: at the tripping speed, it grips its rope and trips the safety gear. On lifts rated above 1 m/s, BS EN 81-20 requires the switch to act before the car reaches the tripping speed; on slower lifts it may act at the same moment.
The tripping speed is set for each lift. BS EN 81-20 requires it to be at least 115 per cent of the lift’s rated speed, so the governor does not trip in normal service, and sets upper limits that depend on the type of safety gear, so the gear can still stop the car safely.
Governors are sealed and set at the factory or by a specialist. Engineers check that the governor turns freely, that its rope is in good condition and correctly tensioned, and that its switch works.
Safety gear.
The safety gear is a pair of gripping devices on the car frame, one on each guide rail. There are two main kinds:
| Type | How it works | Where it is used |
|---|---|---|
| Instantaneous | Wedges or rollers grip the rails almost at once, stopping the car in a very short distance | Only slow lifts: on new lifts, a rated speed of 0.63 m/s or less |
| Progressive | Wedges grip the rails against springs, so the car slows over a longer distance with limited deceleration | Lifts of any speed, and required on faster lifts |
Once it has operated, safety gear stays locked on the rails. It is released by raising the car, and a competent engineer has to return the lift to service, after finding out why it operated and checking the rails and the gear for damage.
Buffers.
Buffers sit in the pit beneath the car and the counterweight. They are not meant to stop a falling car: that is the safety gear’s job. They are there for a car or counterweight that travels past its lowest normal position, for example after a control fault.
| Type | How it works | Where it is used |
|---|---|---|
| Energy accumulation | A spring or polyurethane block compresses and stores the energy | Lifts with a rated speed of up to 1 m/s |
| Energy dissipation | A piston forces oil through small holes, absorbing the energy | Lifts of any speed, and required above 1 m/s |
Oil buffers have a safety switch, so the lift cannot return to normal service until the buffer has extended fully again, and their oil level must be easy to check. Engineers check buffer oil levels and that nothing is stored on or around the buffers in the pit.
Protections added by newer standards.
Lift standards have added protections over time, so a lift’s safety features depend partly on when it was built.
Ascending car overspeed protection
On a traction lift, an empty car is lighter than the counterweight. If the brake failed, the car could run upwards out of control. Ascending car overspeed protection detects this and stops the car, or slows it to a speed the counterweight buffers can take. It can act on the car, the counterweight, the ropes or the sheave, for example as a rope brake, a brake on the sheave or safety gear that works upwards.
Unintended car movement protection
If the car moved away from a floor while its doors were open, someone stepping in or out could be caught. Unintended car movement protection detects the movement and stops the car. On a lift built to BS EN 81-20 it must stop within 1.20 m of the landing. This protection was added to the European lift standards by an amendment in 2009 and has been expected on new lifts since 2012, so older lifts may not have it.
Older lifts may not have these protections. BS EN 81-80 gives a method for assessing the safety of an existing lift against current standards and deciding which improvements to make, and when.
How these systems are checked.
Routine maintenance keeps the safety systems working: engineers clean, lubricate and check the governor, rope, safety gear linkage, buffers and switches. Separately, the law requires the lift to be thoroughly examined by a competent person, who will look at these systems and report any defects.
Some systems also need practical tests, such as tripping the governor and making the safety gear grip the rails. The competent person decides whether and when those tests are needed, and they are often carried out as separate supplementary tests with the maintenance company’s help. SAFed’s LG1 guidelines describe how these tests are done. Our guide to LOLER explains when thorough examinations are due, and our lesson on how to read a LOLER report explains what the examiner reports.
Safety first
Never open lift doors with a release key, enter a lift shaft or pit, or try to free trapped passengers unless you are trained and authorised to do so. If someone is trapped, use the alarm or call your maintenance provider. If anyone is in danger, call 999.
Check your understanding.
Three quick questions on this lesson. Choose an answer to check it, or open the answer below each question.
-
When a car starts to go too fast, what does the governor’s switch do?
Show the answer
B. It opens the safety circuit, which stops the machine and applies the brake. The governor’s switch is part of the safety circuit, so opening it cuts power to the machine and the brake applies. If the car keeps accelerating, for example because the brake or ropes have failed, the governor grips its rope and trips the safety gear.
-
Why does the safety gear work independently of the suspension ropes?
Show the answer
A. So it can stop the car even if the ropes fail. The safety gear grips the guide rails, which are fixed to the building. It can stop the car whatever has happened to the ropes, the machine or the brake.
-
What are buffers for?
Show the answer
B. Stopping a car or counterweight that travels past its lowest normal position. Buffers are the last line of defence at the bottom of the shaft. They absorb the energy of a car or counterweight that travels below its normal end position.
Sources.
The primary sources for this lesson. We checked them when the lesson was last updated on 18 October 2026. How we research and check our lessons.
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Related reading
Questions about the safety of an older lift?
Talk to an engineer about how your lift is protected and what newer safety features it could have.
Common questions.
Quick answers to common questions about this topic.
Can a lift fall down the shaft?
Lifts are designed so that a free fall is prevented. A car hangs from at least two independent ropes, sized with a large safety margin, and the overspeed governor and safety gear stop the car by gripping the guide rails if it goes too fast, independently of the ropes.
What is a lift overspeed governor?
It is a speed-sensing device driven by its own rope, which is connected to the car. If the car goes too fast, the governor opens a switch to stop the machine and, at its tripping speed, grips its rope to pull the safety gear into action.
What happens after the safety gear has operated?
The car is held on the guide rails and a switch keeps the lift out of service. The safety gear is released by raising the car, and a competent engineer must find out why it operated and check the lift before returning it to service.
Do older lifts have the same safety systems as new ones?
Older lifts have the core systems, such as the governor, safety gear, buffers and interlocks, but may lack protections added by newer standards, such as protection against the car moving away from a floor with the doors open. BS EN 81-80 sets out how the safety of existing lifts can be assessed and improved.