Twelve hours’ rest on paper.
Nine once they are home.

How the score is worked out

The figure beside each day on the board is a relative risk. It compares that shift with an eight-hour day shift at the start of a run, which scores 1.00. A shift at 2.25 carries a modelled accident risk two and a quarter times that one. It is not a probability, it is not a measurement of the person working it, and it says nothing about how anybody slept.

Three things move it, and each is a published figure rather than one of ours.

The first is when the shift starts. Folkard and Tucker’s 2003 review in Occupational Medicine found accident risk lowest on morning shifts, about 18% higher on afternoons and about 30% higher on nights. The tool reads a start before noon as a morning, noon until six as an afternoon, and six in the evening until six in the morning as a night.

The second is how long it runs. Risk is flat for the first eight hours and then climbs. The same review puts a ten-hour shift 13% above the first eight hours and a twelve-hour shift 27% above. The curve here is fitted to pass through both of those points exactly. Under eight hours the tool scores 1.00, because the review gives no figure for a shorter shift and inventing one would be worse than leaving it flat.

The third is where the shift sits in a run. Over four successive nights the published increases are 6%, 17% and 36% against the first night. Over four successive day shifts they are 2%, 7% and 17%. The series stops at four. Past that the tool holds the fourth figure and says so in the flags. The honest thing to say about a nine-day run is that it has gone off the end of the evidence.

The three are multiplied together, the way Folkard and Lombardi combined the same components in 2006. Travel, rest and breaks are deliberately not in that multiplication. There is no published coefficient to use for them, so they sit where they belong instead. Travel changes the rest gap. The gap is then checked against regulation 10 and against your own minimum, and the break against regulation 12.

The week the page opens with

Six twelve-hour nights, Monday to Saturday, starting at eight in the evening, with an hour and a half of travel at each end. Nothing about it is unusual and nothing about it is unlawful on its face.

Each shift is twelve hours on site, so the week is 72 hours worked and 90 door to door. The shift finishes at eight in the morning and the person is home at half past nine. The next one starts at eight, and they leave the house at half past six. That is nine hours between one door and the next, and it has to hold a commute, a meal, a shower and a full day’s sleep taken in daylight.

On the timesheet that gap reads as twelve hours. Door to door it is nine, and regulation 10 asks for eleven. Open the week, drop the travel to thirty minutes each way, and the gap reaches eleven exactly while the risk figure does not move at all. Those are two different questions and a rota needs both of them asked.

The risk figure follows the run rather than the week. Monday scores 1.65, a night start at 1.30 multiplied by twelve hours at 1.27. By Thursday the run multiplier has reached 1.36 and the same shift scores 2.25. Nothing about the shift changed. Only its place in the row did.

Which UK businesses have to manage fatigue

There are two answers. Every employer in Great Britain carries the general duty, and a handful of sectors carry a named one on top of it.

The general duty is section 2 of the Health and Safety at Work etc. Act 1974 and regulation 3 of the Management of Health and Safety at Work Regulations 1999: assess the risks your work creates, and control them. Fatigue is one of those risks. The Health and Safety Executive is explicit that keeping inside the Working Time Regulations does not discharge it on its own. HSE puts about 3.5 million people in the UK on shifts.

These are the sectors where a regulator has written fatigue down separately.

Rail and infrastructure

Regulation 25 of the Railways and Other Guided Transport Systems (Safety) Regulations 2006 covers fatigue. The controller of safety critical work must have arrangements so that nobody carries it out while so fatigued that safety could be significantly affected. The Office of Rail and Road enforces it. On Network Rail infrastructure the standard NR/L2/OHS/003 sits on top. Its long-standing limits are twelve hours on a turn, twelve hours between turns, thirteen turns in fourteen days and 72 hours in a week.

Road transport

Drivers of most goods and passenger vehicles work to drivers’ hours rules and to the Road Transport (Working Time) Regulations 2005. Those set 60 hours in any single week and an average of 48 over the reference period, with no individual opt-out. A driver doing night work is limited to ten hours in any 24. Enforced by the DVSA and the traffic commissioners.

Aviation

Flight and duty time limitations for flight and cabin crew, set by the Civil Aviation Authority. An operator working outside the standard scheme needs a fatigue risk management system.

Shipping

The Merchant Shipping hours of work regulations give seafarers at least ten hours’ rest in any 24, and 77 in any seven days. The ten hours may be split into no more than two periods, one of them at least six. The Maritime and Coastguard Agency inspects against it.

Offshore and major hazard sites

HSE has its own operational guidance for assessing shift work, fatigue and working-hours policy offshore. It also treats fatigue as a human factor on COMAH sites, where a single error has consequences well past the person making it.

Healthcare and emergency services

No separate fatigue regulation, but contractual limits on shift length, consecutive nights and weekly hours do the same job, alongside the general duty.

Construction

No fatigue-specific regulation. CDM 2015 puts planning, managing and monitoring on the principal contractor under regulation 13 and on every contractor under regulation 15. A working pattern is part of what is being planned. Where the work is on rail, highways or a client’s major hazard site, that client’s own standard usually bites harder than the law does.

The pattern behind that list is not the industry. It is night work, long shifts, long travel, call-outs and runs of consecutive days. Those turn up in facilities management, utilities, security, manufacturing, logistics, warehousing and care as readily as they do on a railway.

What this does not do

It is not the HSE Fatigue and Risk Index. That is a different model, from research report RR446, and its public spreadsheet was withdrawn in 2021. This page uses the published relative-risk figures from the review that work sits alongside, and shows you every multiplier it applied.

It draws one shift a day, so a call-out on top of a day shift cannot be entered. It knows nothing about the person: sleep, health, age, a second job, a young child, or whether the ninety-minute journey was driven or slept through on a train. It knows nothing about the work either, so a spotter and an operator on the same shift score the same. It does not know when the break was taken, only how long it was. It counts a day at zero hours as a rest day, which a day spent moving house is not.

A score below any threshold is not a finding of fitness for work, and a score above one is not a reason to stand somebody down on its own. Both are a prompt to look at the pattern and to ask the person. This is not legal advice, and it does not make anybody compliant with anything.

When the hours arrive on their own

Every figure on this page was typed by somebody who already knew the answer they were looking for. That is the limit of a calculator. On a site running QR code clock-in the start and finish come from a scan at the poster. The time is written by the server rather than read from the handset. Travel is recorded separately, against its own daily ceiling. The run, the rest gap and the night hours are then properties of a record that already exists rather than a research project somebody has to start on a Friday.

Advanced Fatigue Manager checks that record against the limits your firm has set. It shows the status next to the name in the labour run planner while the next job is being assigned. Both the office and the operative get the alert. The warning, the named decision and any override reason stay with the hours behind them. It puts the pattern in front of the person who can still change it.

Not legal, medical or safety advice. The regulations cited are the Working Time Regulations 1998, regulations 2, 4, 6, 10 and 12, and regulation 25 of ROGS 2006. The duty position is HSE on fatigue and ORR on managing rail staff fatigue. The multipliers are from Folkard S and Tucker P, “Shift work, safety and productivity”, Occupational Medicine 53(2), 2003. The way they combine is from Folkard S and Lombardi D, American Journal of Industrial Medicine 49(11), 2006. The break finding is Tucker P, Folkard S and Macdonald I, “Rest breaks and accident risk”, The Lancet 361(9358), 2003. All checked 22 September 2026.