RMT defines fatigue as the decline in mental and/or physical performance that results from prolonged exertion, lack of quality sleep, or disruption of the internal body clock.The degree to which a worker is prone to fatigue is also related to workload. Work that requires constant attention, is machine paced, complex or monotonous, can increase the risk of fatigue.

A consensus view of scientists who study human performance and safety is that sleep is a powerful and vital biological need. Insufficient and disturbed sleep, chronic sleep loss and being awake for prolonged periods, increases the risk of errors and accidents. Research has shown that staying awake for 17 hours can make people perform as badly as being over the drink drive limit for driving on the road.

Fatigue, night work and/or shift-working arrangements have been cited as major contributory factors in numerous accidents and incidents including, for example, the 1988 Clapham Junction collision which killed 35 people, where staff fatigue caused by excessive overtime was identified as a contributory factor.

Circadian rhythms

This is a 24-hour cycle that virtually all bodily functions have, with a high and low point over the day; for example both body temperature and alertness have a cycle. Humans are programmed to sleep at night and be alert in the day. For shift workers, this means that it is very difficult to fall asleep in the day or keep awake at night.

The hours between 23.00 and 06.00 are when the body naturally wants to go to sleep, with maximum sleepiness between 03.00 and 05.00. Also, between 15.00 and 17.00 is another period when the body naturally wants to sleep.The internal circadian clock also receives external cues from changes between day and night, and between work and social life.

Health impact of shift work

Research has shown that gastrointestinal problems (such as indigestion, abdominal pain, constipation, chronic gastritis and peptic ulcers) and cardiovascular disruption (such as hypertension and coronary heart disease) is estimated to be greater in shift workers than day workers.

Amongst shift workers there is also increased susceptibility to minor illnesses such as colds,‘flu and gastroenteritis.

The International Agency for Research on Cancer has concluded that shift work which involves circadian disruption is “probably” carcinogenic to humans.



Health and Safety at Work Handbook

Reproductive problems in female shift workers have also been reported; the HSE writes “while the association for reproductive effects is less strong, it would be wise to consider shift work, especially night shifts, as a potential risk to reproduction”.

Shift work may also exacerbate existing health problems such as diabetes, asthma, epilepsy and psychiatric illness.Additionally, the effectiveness and potential toxicity of some drugs may vary depending on the time they are taken - as the dose response patterns of many drugs follow a circadian pattern.

Those who have sleep problems will experience excessive tiredness if working long shifts, as well as experiencing other symptoms such as insomnia, disrupted sleep schedules, reduced performance, and may experience irritability/depressed mood and suffer from difficulties with personal relationships. Unfortunately, treatment for these people is limited. Behavioural and pharmacological remedies can help alleviate symptoms; however, it should be remembered that for safety critical work, drugs, even from a pharmacist, can be problematic. Those finding themselves in this situation should always check beforehand whether any proposed medication will be safe for the work they do, including any driving, using machinery or other potentially hazardous work, and record what they are taking with their line management to get an agreed understanding for their use. Also, if driving, they need to be cautious if they are using medication to assist sleeping patterns.

If shift workers have difficulty sleeping during the day, the chances are they will have difficulty staying awake at work.The more tired/fatigued they are, the more likely they are to experience a “micro sleep” (this is an involuntary bout of sleep brought on by sleep deprivation that lasts for a few seconds). Some research indicates that the body may never fully adapt to shift work, especially for those who switch to a normal weekend sleep schedule.

Shift workers, particularly those who work at night, may be at risk of ill-health because shift work can disrupt the body clock (by interfering with the production of hormones by the body), disturb sleep and cause fatigue. In recognition of the particular risks to those working nights, the Working Time Regulations include a right for these workers to receive free health assessments.

Individual and social factors may also contribute to the risk of ill-health effects. Therefore, not everyone will experience or have the same pattern or degree of health problems. An individual’s attitude, behaviour, lifestyle, age, sex and family history plus the conditions they work in, will all play a part.

Long hours also reduce the time available for family, socialising and relaxing, and so can drastically undermine the quality of life and impact health. Fatigue is also associated with increased accident rates and reduced productivity.


Causes of fatigue

The main work-related causes of fatigue include:

  • Long shifts, particularly those that impinge on the normal hours of sleep (e.g., nights and early starts)

  • Rapid turnarounds (e.g. insufficient time available between shifts for rest and recovery)

  • High numbers of consecutive shifts

  • Inadequate breaks within a shift

  • Variability in the shift pattern (e.g. a rotating shift pattern that changes

    about once a week; short notice changes to roster; backward rotating shifts;

    variable shift start times in a sequence of consecutive shifts)

  • Unplanned work (e.g., on-call duties, overtime and emergencies)

  • Commuting time

  • Workload and nature of task

  • Features of the work environment (e.g. temperature, noise and vibration).

The level of work-related fatigue will be similar across individuals performing the same tasks. It should therefore be assessed and managed at the organisational level.

The main non-work-related causes of fatigue include:

  • Domestic and family circumstances that may cause sleep disruption

  • Health (e.g. sleep disorders)

  • Individual differences (e.g. body clock and preferences for certain shifts, age)

  • Strenuous activities (e.g. second jobs)

  • Lifestyle (e.g. diet; alcohol, drugs and recreational activities)

  • Stress (e.g. physical, mental or emotional response to external events)

The above are best managed at the individual level as the impact of different factors will vary considerably. Employers should ensure however that employees are aware of the (non-work-related) risks and know how and where to go for further information and support (e.g. General Practitioner or Occupational Health Department).


Section 2(1) and 3(1) of HASWA places a general duty on employers to reduce risks as far as practicable, including risks from staff fatigue. Section 7 of HASWA requires employees to co-operate with their employer, by for instance ensuring they are adequately rested to do their work safely, and by reporting any concerns to their employer.

The Management of Health and Safety at Work Regulations 1999 place a legal duty on employers to manage any risks from fatigue that arise from work. Fatigue is a risk, like any other hazard, and therefore needs to be controlled through risk assessment and risk management.



Health and Safety at Work Handbook

The Working Time Regulations 1998 (as amended) (WTR) lay down the minimum legal requirements on how to organise working time. Simply complying with the Working Time Regulations alone is insufficient to manage the risks of fatigue. Nor can an employer claim that a person willingly worked additional hours or shifts. The employer must ensure that they are aware of the hours a person works and take action to prevent any risk to the worker or to others – as some patterns could comply with the WTR but still be potentially fatiguing.

For further information, please see the HSE guidance “Managing shift work Health and safety guidance”: https://www.hse.gov.uk/pubns/books/hsg256.htm, which explains how to comply with the law and contains a ‘fatigue risk index’.

In addition to the more general duties under HASWA and WTR, the Management of Health and Safety at Work Regs – the Railways and Other Guided Transport Systems (Safety) Regulations 2006 (ROGS), Regulation 25 also applies – as this includes a specific fatigue management duty on railway operators to make arrangements to manage the risks arising out of fatigue and long hours of their staff who carry out safety critical duties.

The ROGS superseded the railway group standards, GH/RT 4004 (a standard which incorporated the ‘Hidden Limits’ from the inquiry into the Clapham Junction rail crash, but which was insufficient to address all the known causes of fatigue).

ORR guidance ‘Managing Rail Staff Fatigue’ (MRSF)

See https://www.orr.gov.uk/media/10934

This ORR guidance is aimed at companies and individuals who have responsibilities for managing fatigue under the ROGS, regulation 25.Whether those being managed are safety critical or not, the same principles can be applied for responsibly managing fatigue in transport workers. The guidance explains what a Fatigue Risk Management System (FRMS) should look like and describes the roles and responsibilities, policies and procedures of all staff who work within the system.The guidance includes a nine-step approach tool that can be used in the management of fatigue (a nine-step approach which is also applicable to other industries).

Also see the ORR Good practice guidelines – Fatigue Factors, at: https://www.orr. gov.uk/sites/default/files/2021-12/good-practice-guidelines-fatigue-factors.pdf this specifies what fatigue factors should be considered where there is no role-specific guidance in place.

MRSF adopts a “triangulation” approach to assessing likely fatigue from a working pattern, the three stages of which are:

• Comparing the working pattern against good practice guidelines to identify potentially fatiguing features



  • Using a bio-mathematical tool

  • Getting feedback from staff on how fatiguing they actually find the work pattern

    Fatigue is a particular concern in safety critical staff as they may not be aware that their performance is being compromised as there is no test for fatigue and so it can be difficult to detect. In workplaces where fatigue of workers is a factor there are likely to be increases in the likelihood of errors and adverse effects on performance, especially in tasks requiring:

  • Vigilance and monitoring

  • Decision making

  • Awareness

  • Fast reaction time

  • Tracking ability

  • Memory

    All employers should have management arrangements to control the risks from staff fatigue.The complexity of those arrangements will depend on the type of work being carried out, whether work is safety critical or not, and overtime arrangements.The table below sets this out in relation to how to use the ORR’s MRSF guidance document:


Type of work

No shift work, no significant overtime, no ROGS safety critical work

Some shift work and/or significant overtime but no ROGS safety critical work

ROGS safety critical work

Likely significance of risks


Medium to high


Relevant sections of this from fatigue guidance

Section 4
“Basic fatigue controls”

Section 5 “Fatigue Risk Management Systems”

Section 5 “Fatigue Risk Management Systems”
Section 6 “Managing fatigue in ROGS safety critical work

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Fatigue Risk Management System (FRMS)

Key to the effective management of fatigue is the development of a FRMS. The ORR guidance sets out what a FRMS is, the features such a system should have, and how the FRMS should integrate with other risk control systems.

It is crucial that managers take a collaborative approach, involving staff and consulting other relevant parties such as trade unions in devising and setting up


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controls to eliminate or reduce the factors which contribute to fatigue.This is the approach outlined by the ORR in the third prong of their triangulation approach.

Controls may include, for instance: shorter shifts; fewer successive shifts without a rest day; steps to reduce short-notice variations in planned start times; and enhanced fatigue education and training. Staff and their trade union representatives should co-operate with employers in ensuring that risks from fatigue are properly controlled.

The FRMS should have a number of components and stages:

  • Fatigue Policy

  • Organisational issues

  • Planning and implementing

  • Measurement

  • Audit and review

    Fatigue assessment tool

    Some companies use a Fatigue Risk Index, which provides an estimate of likely levels of fatigue and risk associated with working patterns depending on a number of different data being inputted.This type of index is normally used for shift-working/rosters.

    If a company is using an index, the safety reps should familiarise themselves with the system it uses and ask for training on the index, especially if they are negotiating or scrutinising rosters. For more information on fatigue risk indicators, please see HSE information on the development of a fatigue/ risk index for shift workers at https://hse.gov.uk/research/rrhtm/rr446.htm.

    When using a fatigue assessment tool, it is important to understand and think carefully about what the output means, rather than to blindly assume it produces an authoritative “satisfactory/ unsatisfactory” decision.The use of a mathematical Fatigue Risk Index can be used by employers in a way that punishes some groups of workers, with reports that they are being utilised to cut shift lengths so that workers have to do more shifts per year in total.Working more shorter shifts can lead to higher levels of fatigue if there is an increase in journeys to work and less time away from work. It must also be remembered that fatigue modelling is merely one component of the fatigue management system and should never be used as a stand-alone product.

    According to the ORR Guidance:

    The Fatigue Index represents the estimated probability, expressed as a percentage, that a person working the pattern concerned will feel very fatigued at some point during the shift.A fatigue index of 10 therefore means that on average, 1 in 10 people working that pattern are likely to feel very tired.Although this is clearly more desirable than a fatigue



index of 50 (meaning half the people are likely to feel very tired), it does not mean that a fatigue index of 10 is risk-free. But it does indicate which of the two working patterns is likely to be less tiring.

To summarise as regards the fatigue index, the ORR writes “fatigue assessment tools cannot model all the factors which affect fatigue”.

Fatigue policy

At the heart of the FRMS there should be a statement of the organisation’s overall policy on fatigue.The policy should recognise that the effective management of fatigue is a collaborative process. Senior management should be committed to involving staff and the trade unions in devising, implementing and monitoring effective fatigue risk control measures. There must be a “buy-in” from staff, and the FRMS policy should recognise that the organisation may need to invest time upfront to help “sell” the need for, and benefits of, the co-operative FRMS approach to staff and their representatives.

The policy should also explain the company’s overall commitment to managing fatigue, include the status of any relevant company standards and limits, and their relationship to any relevant negotiated agreements with trade unions, for instance terms and conditions of employment.

Additionally, the policy should explain how the organisation will collect and use data on fatigue and its effects, including the fatigue reporting system for reporting errors, adverse events and concerns which could have a fatigue element, staff education and training on fatigue and explain that there will be a periodic review of fatigue controls, and if there is reason to doubt their effectiveness what will be done to address this.

Input from trade unions

Key to ensuring that fatigue risks are properly controlled in the rail industry is input from the trade unions via their Health and Safety reps. Fatigue risks cannot be properly managed alone so employees and trade unions have their own important responsibilities in controlling the risks from fatigue.

Trade unions should, for example:

  • Co-operate with an employer’s reasonable efforts to ensure that risks from staff fatigue are adequately controlled

  • Make reasonable efforts to ensure that fatigue risk management good practice is taken into account by their representatives during negotiations on working patterns and other issues having a bearing on the control of fatigue risks

  • Consider whether pay structures could inadvertently be encouraging fatigue – is low pay encouraging excessive overtime?


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  • Examine whether existing terms and conditions of service have taken full consideration of possible fatigue effects

  • Receive training for negotiating working patterns

  • Ensure that the employer carries out a ‘reality check’ by seeking staff

    feedback on working patterns

  • Ensure that an open “just” culture exists whereby if staff feel too tired to

    work safely (e.g. a new baby at home keeping them awake) they will not be punished for declaring this so that alternative arrangements can be made.

    Safety critical work

    If the employer’s undertaking involves safety critical work then, in addition to the FRMS, there will need to be applied the requirements of the ROGS regulation 25, which states:

    Every controller of safety critical work shall have in place arrangements to ensure, so far as is reasonably practicable, that a safety critical worker under his management, supervision or control does not carry out safety critical work in circumstances where he is so fatigued or where he would be liable to become so fatigued that his health or safety or the health or safety of other persons on a transport system could be significantly affected.

    The regulation also requires the undertaking to have a “controller of safety critical work”, who should establish effective arrangements for managing the risks arising from fatigue from safety critical workers.This process shall follow the following steps:

  1. (1)  Identifying those safety critical workers affected

  2. (2)  Setting standards and designing working patterns

  3. (3)  Limiting exceedances

  4. (4)  Consulting with safety critical workers

  5. (5)  Recording the arrangements

  6. (6)  Providing information to safety critical workers

  7. (7)  Monitoring

  8. (8)  Taking action when safety critical workers are fatigued

  9. (9)  Reviewing the arrangements

The ORR guidance provides detailed commentaries on each of these nine stages. RMT representatives should be fully involved in stage 2 – setting standards and designing working patterns; stage 4 – consulting with safety critical workers; stage 6 – providing information to safety critical workers; stage 7 – monitoring; and stage 9 – reviewing the arrangements.The guidance concludes with a series of appendices which give important information on a number of issues: fatigue risk assessments, travel time, features of a positive safety culture, and fatigue reporting.


In summary, the key principles in fatigue are as follows:

  • Fatigue needs to be managed, like any other hazard and risk

  • It is important not to underestimate the risks of fatigue, for example, the number of errors, accidents and injuries has been found to be higher on night shifts, after a succession of shifts or when shifts are long and there are inadequate breaks; this rises with increasing shift lengths over eight hours

    and increases over successive shifts, especially if they are night shifts

  • The legal duty is on employers to manage risks from fatigue, irrespective of any individual’s willingness to work extra hours or preference for certain shift patterns for social reasons. Compliance with the Working Time Regulations

    alone is insufficient to manage the risks of fatigue

  • Changes to working hours need to be risk assessed and, where change is

    required, then the changes to be notified in advance

  • Employees and RMT representatives should negotiate and agree rosters and

    be consulted on working hours and shift patterns. However, note that where employees state a preference for certain shift patterns that are potentially unhealthy and may cause fatigue, then these preferences must be managed to ensure the risks to workers are suitably controlled

  • A policy must be developed that specifically addresses and sets limits on working hours and patterns, overtime and shift-swapping, and which guards against fatigue.Then implement the policy and make arrangements to monitor and enforce it; this may include developing a robust system of recording working hours, overtime, shift-swapping (shift exchange) and on-call working

  • Problems with overtime and shift-swapping may indicate inadequate resource allocation of staff or just a shortage of staff with vacancies unfilled

  • How long people have been awake must be a key consideration, as long journeys to work mean staff may become unfit to work later in the shift

  • Age: older workers are better at early morning shifts, but struggle with


  • There are many different shift work schedules, and each schedule has

    different features.The sheer diversity of work and workplaces means that there is no single optimal shift system that suits everyone. However, a planned and systematic approach to assessing and managing the risks of shift work can improve the health and safety of workers.A guiding principle must be a shift system of ‘rotation forward not back’

  • Sleep disturbances can lead to a ‘sleep debt’ and fatigue. Night workers are particularly at risk of fatigue because their day sleep is often lighter, shorter and more easily disturbed because of daytime noise and a natural reluctance to sleep during daylight. If an individual loses one hour’s sleep a day/night, then over the week they will have lost seven hours - and that is a full ‘night’s sleep’; do that over a three-month period and you have lost twelve ‘nights of sleep’.



Health and Safety at Work Handbook

For shift working to be successful, you need to maintain a satisfactory level of productivity and safety. Fatigued shift workers may perform less well than those working standard daytime hours, especially during periods of low alertness. The consequences of this could range from relatively minor events to serious accidents.

Road vehicle transport/bus and taxi

In the context of vehicle control, fatigue can be accompanied by poor judgement, slower reactions, and decreased skill levels. Importantly, fatigue can impair a driver’s judgement of his or her own state of fatigue. Driver fatigue is one of the biggest health and safety concerns within the road transport sector.

Well-documented indicators of driving fatigue are:

  • Not feeling refreshed after sleep

  • Falling asleep at work

  • Loss of concentration at work, leading to increased errors, such as drifting

    out of lane when driving

  • Poor visual perception in poor light/weather conditions

  • The need for extended sleep during days off.

    Driver fatigue is associated with very poor/poor self-rating of quality of sleep,drinking three or more caffeinated drinks daily, and driving more than ten hours a day.

    Research shows that a considerable proportion of vehicle accidents are sleep related and it is believed that up to 20% of serious accidents are caused by fatigue. There are strict rules governing the amount of hours that PSV/PCV and HGV drivers can work; however, these still do not prevent fatigue from occurring.

    For information on drivers’ hours see: https://www.gov.uk/drivers-hours

    HGV/PSV drivers who drive only in the UK (under 50 miles) are governed by UK domestic driving limits, whereas those who travel within the EU or drive vehicles over 3.5 tonnes need to abide by EU limits which are more stringent than UK domestic laws. Currently, the maximum hours at the wheel without a break for UK PSV/HGV drivers is 5.5 hours, whereas the EU limit is an hour less at 4.5 hours.

    Fatigue may be more of a problem for coach drivers due to longer driving distances on motorways but given the number of distractions and high level of concentration needed by urban bus drivers, fatigue is also an issue for this group of workers.

    Fatigue can be effectively managed by a Fatigue Risk Management System (FRMS). This is a scientifically based data-driven system which manages employee fatigue in a flexible manner appropriate to the level of risk exposure and the nature of the operation. A FRMS can be used in addition to prescriptive hours of work limitations.The traditional method of mitigating driver fatigue has been to limit a driver’s time at the wheel.



Car drivers are generally encouraged to take a 15-minute break every two hours of driving, and the same should be applied to bus and coach drivers.What also needs to be taken into consideration is that drivers have other duties besides driving. For the most part they must also check the vehicle for defects and, in the case of coach drivers, emptying toilet tanks is another task that may need to be done.

In conclusion, fatigue is a serious issue that needs to be managed effectively. Any FRMS should include consultation with union reps who will look at rosters, time off and risk assessments to ensure that fatigue is being managed properly. The result of not managing fatigue correctly is a reduction in safety which in turn can lead to accidents – some of which are devastating and fatal.