Fall arrest vs work restraint: what actually differs
Work restraint physically prevents the wearer from reaching a position where a fall is possible. Fall arrest allows the fall to happen and then stops it, within a calculated clearance distance. The hardware looks similar and the logic is completely different, which makes confusing the two one of the more dangerous mistakes in height safety procurement.
The consequence sits in the word "calculated". A restraint system works by geometry: the lanyard is short enough that the user cannot reach the edge. A fall arrest system only works if there is enough empty space below the wearer for it to operate, and on low-level work there often is not.
- Work restraint stops you getting into a position from which you could fall. Fall arrest stops you after the fall has started.
- Restraint is preferable wherever the work allows it, because nothing has to perform correctly under load for it to have worked.
- Fall arrest needs verified clearance below: lanyard length, energy absorber deployment, the wearer's height below the attachment point and a safety margin.
- EN 355 absorbers limit arrest force to 6 kN and must not deploy beyond 1.75 m. A plain EN 354 lanyard with no absorber is a restraint component, not a fall arrest one.
- Only an EN 361 full body harness may be used for fall arrest, and a rescue plan must be in place before work starts.
Where each one sits in the hierarchy
The Work at Height Regulations set an order of preference, and personal fall protection is near the bottom of it. In HSE's terms: avoid work at height where reasonably practicable, prevent falls where the work must happen, and only then minimise the distance and consequences of a fall.
Collective protection comes before personal protection, because collective measures work without the person doing anything. A guard rail protects everyone on the platform whether or not they clipped on. A harness protects one person, and only if they wore it properly and chose a sound anchor.
- Work restraint is a prevention measure. The fall never starts.
- Fall arrest is a minimisation measure. The fall starts and the system limits what it does to the person.
Restraint is not simply the cheaper option. It sits a step higher in the hierarchy, so where a task can be done in restraint, choosing arrest instead is hard to defend.
How restraint is set up
Restraint is measurement rather than energy management. Anchor position and lanyard length are chosen together so the user's reach stops short of every edge and opening. HSE's guidance is direct: the lanyard length should be set or adjusted so the user cannot get into a situation where fall arrest is required, and that applies to fixed length, adjustable and retractable types alike.
- An adjustable lanyard used in restraint must be locked at the correct length and checked, or it silently becomes a fall arrest situation.
- Restraint depends on the anchor staying where it was planned. Moving it changes the reach envelope and can invalidate the arrangement.
Because nothing is arrested, restraint anchors are often rated below fall arrest anchors. Never assume a restraint anchor is suitable for arrest.
Clearance, the calculation that decides whether arrest can work
A fall arrest system needs a defined amount of unobstructed space beneath the wearer. If ground, a slab, plant or scaffolding sits inside that distance, the person hits it before the system has finished working. The distance is made up of:
- the lanyard length, or the payout of the retractable device;
- the deployment of the energy absorber, which under EN 355 may extend by up to 1.75 m;
- the wearer's height below the harness attachment point, since the feet arrive first;
- a safety margin below the lowest point reached.
Added up, the required clearance is commonly several metres. On tank tops, shallow pits, low gantries and much MEWP work the space is not there, which is why restraint or collective protection is so often the only workable answer at those heights. Do not estimate it: every fall arrest product is supplied with instructions stating the clearance required for that configuration.
Components, and the errors that keep recurring
- Using an EN 354 lanyard over a drop. EN 354 covers lanyards, EN 355 covers the energy absorber that limits the force reaching the body. A plain lanyard is a restraint component; clipping one above a drop transmits the full arrest force to the wearer.
- Using a belt or sit harness for arrest. An EN 361 full body harness is the only body holding device permitted for arresting a fall.
- Assuming an anchor is rated. Confirm suitability for fall arrest with whoever is responsible for the structure or equipment, particularly on MEWPs, where suitable arrest anchors are frequently absent.
- Buying with no inspection regime. Harnesses and lanyards need documented pre-use checks, periodic inspection by a competent person and removal from service after any arrested fall.
Rescue is part of the system
Arresting a fall leaves someone suspended in a harness, conscious or not, and that is time critical. HSE expects employers to plan for emergencies and rescue and to make sure workers know the procedure, rather than relying entirely on the emergency services.
So if fall arrest appears in a method statement, so should three answers: who performs the rescue, with what equipment, and how quickly they can reach the casualty. If those answers do not exist, the system is incomplete however good the hardware is - and that is a reasonable prompt to ask again whether the task could be done in restraint, where the question never arises.
Common questions
What is the difference between fall arrest and work restraint?
Work restraint prevents the wearer reaching a position where they could fall, by limiting lanyard length and anchor position so the edge is out of reach. Fall arrest permits the fall and then stops it within a calculated distance, using an energy absorber to limit the force on the body. Restraint prevents the event; arrest limits its consequences.
How much clearance does a fall arrest system need?
It must be calculated, not estimated. Add the lanyard length or device payout, the energy absorber's deployment, which under EN 355 can reach 1.75 m, the wearer's height below the harness attachment point, and a safety margin. The total is commonly several metres. Use the figure in the manufacturer's instructions for that configuration.
Can I use a work positioning belt for fall arrest?
No. Only an EN 361 full body harness may be used to arrest a fall. Work positioning belts and sit harnesses support a worker in position rather than absorbing and distributing arrest forces, and using one for arrest can cause serious injury. Fall arrest attachment points on a harness are marked and should be the only ones used.
Is a restraint lanyard the same as a fall arrest lanyard?
No. A plain lanyard to EN 354 has no energy absorber, so it is a restraint component. A fall arrest lanyard incorporates an EN 355 energy absorber, which limits arrest force to 6 kN and deploys by up to 1.75 m as it does so. Connecting a plain EN 354 lanyard above a drop is a serious and common error.
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