The aim of this guidance is to support persons conducting a business or undertaking (PCBUs) in managing risks from shift work.
1.1 Who is this guidance for?
The purpose of this guidance is to support people to manage the risks of shift work. This guidance is intended for persons conducting a business or undertaking (PCBUs), although many different audiences (such as workers, supervisors, managers, Health and Safety Representatives (HSRs), and unions may find the information useful.
You have a duty under the Health and Safety at Work Act (2015) (HSWA) to ensure, so far as is reasonably practicable, the health and safety of your workers, and any other workers who are influenced or directed by the business.
Workers also have a duty to take reasonable care of their own health and safety. This means that both you and workers should work together to deal with the risks of shift work, including mental and physical fatigue.
For more information on HSWA duties, see Appendix 1 of this guidance.
2.0 What is shift work?
Shift work is any type of work that requires a worker to be awake when they would normally be asleep.
2.1 What is shift work?
Shift work is any type of work that requires a worker to be awake when they would normally be asleep. Shift work might involve:
- permanent, rotating, changeable, non-standard, irregular, or unpredictable work hours
- early starts
- late finishes
- night work.
Long hours that span the traditional work day can also be shift work, when they include early starts and/or late finishes that require a worker to be awake when they would normally be asleep.
2.2 Why manage shift work?
Shift work causes fatigue. Fatigue is a physiological state where someone is unable to mentally and physically function at their best. Fatigue is caused by four main things: missing out on sleep, being awake for too long, working and sleeping in the wrong parts of the circadian body clock cycle, and workload (physical and mental).
For more information on fatigue, see Appendix 7 of this guidance.
Together, shift work and fatigue can contribute to:
- poorer mental and physical health
- lower level of functioning
- increased likelihood of incidents or injuries
- increased turnover and sick leave absences.
Poorer mental and physical health
Shift work increases the likelihood of developing several physical health problems.
In the short term, shift work can lead to:
- gastrointestinal problems, such as indigestion, abdominal pain, and constipation
- increased chances of catching colds and flus
- shortened and/or poorer quality sleep.
In the long-term, shift work can increase the likelihood of:
- gastrointestinal problems, such as peptic ulcers
- sleep problems, such as insomnia
- becoming obese
- developing colorectal, lung and breast cancer
- developing cardiovascular disease, including hypertension and coronary heart disease
- developing type 2 diabetes
- having a stroke
- early death.
Shift work may also increase the likelihood of mental health problems such as depression and psychological distress.
Lower level of functioning
The fatigue that results from shift work can severely affect workers’ ability to work safely and effectively. Fatigue leads to:
- lower level of overall performance, including slower reaction speeds, making more mistakes, larger decreases in performance across continuous work, and unstable performance
- slower information processing
- poorer short-term and working memory
- poorer decision making
- reduced ability to solve problems
- increased irritability, mood swings, and inappropriate responses in challenging situations
- less effective communication.
Increased likelihood of incidents and injuries
Shift work can increase the likelihood of incidents and injuries at work, including when driving for work, and during the commute to and from work.
The incident rate is higher during evening and night shifts (compared with morning shifts). The likelihood of having a car crash increases when drivers are sleepy, driving at night, or have had less than seven hours sleep in 24 hours. ‘Drowsy driving’ is more likely for shift workers who drive at night, and those who have early morning starts.
The incident rate goes up as the hours at work increase.
Increased turnover and sick leave absence
The relationships between shift work and turnover/sick leave depend on many factors, including work patterns, culture and environment. However, consistently working for more than 40 hours per week, regularly having short recovery periods between shifts, and/or regularly working more than two consecutive night shifts, can lead to increased sick leave.
3.0 Risk management
Put robust fatigue risk management processes in place to support initiatives to identify, assess, and manage risks from shift work, as well as monitor control measures.
It is important to understand the effects of shift work on people. This will help you in assessing the risks of shift work and putting control measures in place to manage them.
Figure 11 shows the links between shift work, sleep, long periods of wake, the circadian body clock and fatigue. Shift work often means peoples’ sleeping patterns are disrupted, which leads to the worker becoming fatigued. High and low workload can lead to fatigue if a person is working at less than ideal times in the circadian body clock cycle or experiencing sleep loss. These things all contribute to fatigue.
For more information on sleep loss (missing out on sleep), extended wakefulness (being awake for too long), circadian disruption (working and sleeping in the wrong parts of the circadian body clock cycle), and the role of workload, see Appendix 7 of this guidance.
3.1 Put the right processes in place
To manage the risks of shift work, put robust fatigue risk management processes in place. These processes should support initiatives to identify, assess, and manage the risks of shift work, as well as monitor control measures to check that they are working. These processes should be a continuous loop of activity, as shown below.
Engagement with workers and their representatives
You must engage with your workers and enable them to participate in improving health and safety. People who carry out the work usually have the best insight into the risks present in their workplace.
One way you could engage with workers (if reasonably practicable for your circumstances) is by creating a working group that includes workers and their representatives. Examples of these group members could be union members and delegates, HSRs, supervisors, managers, and experts on shift work. Involve the working group on an ongoing basis when creating and rolling out fatigue risk management processes.
For more information on worker engagement, participation and representation, see Appendix 4 of this guidance. Or, visit our worker engagement and participation page.
Establish management commitment before putting fatigue risk management processes in place. By confirming this commitment from the start, you can make sure there is enough resourcing, chains of responsibility are in place, and there is championship for shift work management within the business. It also ensures that there is clear support for initiatives to manage the risks of shift work.
3.2 Identify and assess risks
You must ensure, so far as is reasonably practicable 2, the health and safety of workers, and that other people are not put at risk by work. If it is not reasonably practicable to eliminate the risks of shift work, you must minimise those risks, so far as is reasonably practicable.
See below which provides some suggestions about identifying and assessing risks:
Use data sources
To identify the risks of shift work, consider a range of information.
Use data sources to identify risks and monitor the effectiveness of control measures. Examples of sources of information that you could use include:
- the work patterns (including when actual hours differ from rostered hours)
- reports of fatigue, incidents and near misses
- overtime records
- incidents of sick leave or other absenteeism, and staff turnover
- increases/decreases in performance and productivity
- other assessment tools and techniques, including validated questionnaires and staff surveys.
Look for patterns among different sources of information, and use the insights to minimise risk.
Consider the particular risks that come with shift work:
Carry out a thorough risk assessment. Consider all the risks, and how likely it is that workers could be harmed. There are some risks listed in the ‘Smart Rostering’ section of this guidance. For information on how to carry out a risk assessment, see Appendix 5 of this guidance.
Gather and evaluate information about current shift work arrangements, using the sources of information above.
Use the expertise of workers to identify and assess risks.
- who might be exposed to risks
- what the potential consequences of exposure to risks are
- how likely the consequences are.
Work out who might be harmed by shift work
Work out who is most vulnerable to the risks of shift work. While all workers who carry out shift work are at risk, certain groups are more likely to be harmed. These people could include:
- younger or older workers
- pregnant workers and new parents
- workers with chronic illnesses or pre-existing health conditions made worse by shift work
- workers taking time-dependent medication
- non-permanent, casual workers who are not accustomed to your business’s shift schedules
- workers who might already be fatigued
- workers carrying out safety-critical or dangerous work
- workers who, following a standard day’s work, have remained on call through the subsequent night or weekend.
There is a fatigue identification tool in Appendix 6 of this guidance, which you may find useful when considering risks. For more information on identifying and assessing risks, see our how to manage work risks guidance page.
3.3 Minimise risks
When minimising risks, the kinds of control measures will depend on:
- the risks of the work
- the work culture and environment
- the type and structure of your business, and
- the people carrying out the work.
Apply smart rostering and shift work design
One important tool you can use to manage risks is smart rostering and design of the shift work. The shift roster has a big impact on how workers are affected by their work and working hours. However, smart rostering/shift work design, by itself, will not prevent fatigue and other shift work-related risks. Other control measures are also needed to effectively manage risks.
There are many different work schedules, and each one carries its own risks. There is no perfect schedule.
Figure 3 below outlines the things you should take into account when designing rosters and shift work. The key points for each aspect, as well as suggested actions you could take, are detailed in the tables below.
Think about the physical and mental demands of the role
- Workers with a balanced workload will be more efficient, effective and less fatigued than those who are overloaded or underloaded.
- Concentration and productivity may decline towards the end of a shift, after lunch, and overnight, with the lowest level of functioning usually experienced between 3–5am.
- You must provide shift workers with appropriate amenities such as kitchen facilities, rest areas and first aid facilities. See our guidance for more information on these workplace requirements.
- You must make sure lighting levels are appropriate for the type of work being carried out. There should be enough light for night shift workers to work safely, as well as to arrive at and leave work safely.
- Plan an appropriate workload with workers, taking into account the length and timing of the shift. Add more break times if long shifts cannot be modified.
- Schedule demanding work for times when workers are most alert and least likely to be fatigued.
- Avoid scheduling dangerous work during the night, in the early hours of the morning and towards the end of a shift, where reasonably practicable.
- Add more workers for demanding work, or if this isn’t reasonably practicable, schedule shorter shifts.
- Rotate workers through different work stations regularly, if reasonably practicable. Not only does this help to reduce fatigue, it helps to improve workers’ skills and knowledge in different areas.
- Think about the physical nature of the work, repetitive activity, cognitive demands, isolated workers, environmental factors and training/competency.
- Monitor the temperature of the work area to make sure that it is at an appropriate level for the type of work being carried out, or make sure workers can control the temperature of the work area themselves. For more information on thermal comfort at work, see our guidance.
- Be aware of physical factors that can contribute to fatigue, such as noise and vibration.
- Ensure that workers have access to telephones or alarm systems, and consider installing security cameras or hiring security staff.
Think about the work activity
- Rotating sedentary mental tasks with physical tasks can help temporarily reduce the effects of fatigue during a shift.
- Schedule a variety of tasks into the shift plan, where reasonably practicable.
- Allow workers to have some choice over their work activities and the order in which they are carried out.
- Rotate a variety of work activities to reduce the likelihood of workers being continuously exposed to high or low workload tasks, which can lead to them becoming fatigued
Think about the shift pattern
|Type of shift||Key points||Suggested actions|
Avoid scheduling permanent night shifts if reasonably practicable.
|Timing of shift||Key points||Suggested actions|
Night shifts are extremely disruptive. They cause sleep loss, lighter sleep during the day, and mean that people are working at less functional times in their circadian body clock cycle. They can increase the likelihood of error, accident, injury, and poor health and wellbeing.
Night shifts can significantly disrupt workers’ family and social lives.
Time-on-task fatigue can build up faster during the night, meaning that demanding tasks will increase the likelihood of fatigue.
Night work can result in limited training opportunities for workers.
Night work can result in reduced communication between night shift workers and other workers.
You must provide training and information about the risks of shift work to night workers.
No matter the time of day work is carried out, you must provide and maintain facilities for workers.
Avoid scheduling permanent night shifts, where reasonably practicable.
|Early morning starts||
Early morning starts can cut night time sleep short.
If not essential for business needs, try to avoid shift starts before 7am.
Afternoon starts are better than working at night or in the early morning.
Schedule afternoon starts rather than night or early morning starts.
|Daytime shifts||Daytime shifts are the best type of work. They do not disrupt the internal body clock, or reduce contact with family and friends.||Schedule daytime shifts rather than night or early morning shifts, where reasonably practicable.|
|Duration of shift||Key points||Suggested actions|
|8-11 hour shifts||
Shifts up to 8 hours in length are considered to provide more time for rest (including sleep),
|Schedule shifts no longer than 8 hours when the work is monotonous, mentally or physically demanding, or isolated.|
|12 hour shifts||
12 hour shifts can increase the likelihood fatigue, depending on the type and duration of work
The below points apply to any shift longer than 8 hours.
|Shifts long than 12 hours||
The longer the shift, the more the likelihood of fatigue will increase.
Avoid scheduling shifts of more than 12 hours.
|Flexibility in shift length||Flexible start and finish times are popular among workers with commitments outside of work. However, scheduling may be more complex, and will require careful planning and engagement with workers, to ensure risks are
managed and monitored.
|Consider if variable shift lengths, or flexible start and finish times, could work.|
Split shifts can lengthen a working day, and can increase the likelihood of fatigue if the rest break between shifts is too short.
Avoid split shifts if reasonably practicable.
|Duration of shift||Key points||Suggested actions|
|Rest breaks within shifts||
Frequent short breaks can reduce fatigue, improve productivity and may reduce the likelihood of errors and accidents.
Encourage workers to take frequent and regular breaks to minimise the likelihood of fatigue.
|Rest breaks between consecutive shifts||
The likelihood of fatigue is increased when the breaks between shifts are too short.
|Give workers enough time in their rest breaks between shifts to recover from their shift,
commute, eat well, sleep, and participate in social/domestic activities.
Rest days are opportunities for unrestricted sleep. A person usually achieves unrestricted
In general, set a limit of five to seven consecutive working days for standard shifts.
Schedule enough rest time for workers carrying out on-call/standby duties. Workers who are on-call experience disrupted sleep and poor sleep quality, regardless of whether they are called in to work or not. Recovery opportunities following periods of on-call work are necessary.
Napping at work
Napping at work is an effective strategy for temporarily reducing the effects of fatigue, including before driving home from work. However, it should not be used as a routine strategy for extending shifts, and it requires policy and procedures around its use.
Massey University’s Safer Nursing 24/7 Code of Practice(external link) provides the following guidance for workplace napping:
- encourage workers to submit a fatigue report when needing to nap at work. Ensure this process is simple so that napping is not discouraged.
- do not allow workers to use napping at work for enabling extended shifts on a regular basis
- ensure workers advise the shift supervisor where and when they plan to nap, and when they return to work
- ensure that napping only happens during a break when it has been cleared with the shift supervisor, to ensure that the worker’s absence does not increase the likelihood of fatigue for others on the shift
- ensure that workers do not spend any more than 40 minutes trying to sleep during a nap, and that they allow time to recover from the effects of sleep inertia
- cover napping procedures in shift work and fatigue training
- provide suitable facilities for napping.
Have clear policies and procedures
A policy is an effective way to communicate your business’s approach or commitment to managing the risks of shift work. Include information about:
- the fact that shift work is a contributor to fatigue, and that it can have negative effects on worker health and safety
- adequate resourcing to develop and maintain fatigue risk management processes
- roles and responsibilities of management, supervisors and workers
- organisational commitment to strategies to support the fatigue risk management processes, including adequate staffing, training, and communication to all levels of the business
- commitment to review the policy within a set timeframe.
In other procedural documents, record information about:
- shift work arrangements (specific work patterns)
- processes regarding overtime or calling workers back
- control measures for specific risks, tasks, jobs, and operations
- self and peer assessment checklists
- procedures for reporting fatigue risks
- procedures for supporting fatigued workers.
Develop your policies and procedures with your shift work and fatigue working group, if you have one.
Business.govt.nz, along with Employment New Zealand and the Ministry of Business, Innovation and Employment, have created a policy building tool which you may find useful in helping to build your fatigue policy(external link).
Ensure workers know what to do if they have a problem
Workers need to know who can help them if they have concerns about their shift work.
- Clearly identify the right people for workers to speak to about the shift work (this could be a manager, HSR, trusted mentor/buddy or someone else).
- Make it clear and obvious to workers what to do if they cannot find a solution.
- Put an open, supportive, ‘no-blame’ culture in place. It is important that workers feel they are able to safely report and speak about fatigue (or other ill effects of shift work) without fear of negative consequences.
- Have processes and policies that explain what will happen when workers report fatigue or ill-effects of shift work, and make sure these are freely available to workers.
Set up effective and ongoing ways for risk reporting
Establish a system to support reporting of shift work and fatigue-related risks, problems, and incidents. This system should involve:
- including fatigue as an option on near-miss and incident report forms
- thoroughly investigating fatigue as a factor when looking at incidents. Encourage early reporting so that problems can be dealt with quickly and effectively.
Set up effective and ongoing methods of communication
Communication is essential for effective management of shift work and fatigue, and needs to be clear, planned, ongoing, and in place from the start. Everyone in the business needs to be aware of:
- policies and procedures
- their roles in the fatigue management process, and
- where to find support and resources.
Effective processes around communication are particularly important when looking at shift handovers. Have workers work together or in teams, and encourage workers to look out for each other.
If someone must work alone, make sure they always have a way of communicating with others. See our guidance for more information on lone workers.
Provide training for workers at all levels
Training on shift work and fatigue is vital at all levels of a business. It promotes productive and constructive conversations around identifying and assessing the risks of shift work, and putting control measures in place.
Training ensures that workers can make informed decisions about how to use time away from work, including sleep opportunities, and how to use strategies at work to temporarily reduce the effects of fatigue.
As an essential component of fatigue risk management processes, training ensures everyone in a business can participate in health and safety processes, including reporting of risks. Training needs to be tailored for different organisational groups, depending on their specific role.
3.4 Check control measures are working
Identifying, assessing, managing, and monitoring risks is a continuous loop of activity. Control measures need to be re-assessed when new tasks, equipment, procedures or work schedules are introduced, and changes are proposed to the work environment or work schedule.
Control measures need to be reviewed if there is any indication that they are not effective.
Suggested actions are outlined below:
|Monitor any changes to shift work schedules and/or work conditions||Making changes to schedules or work conditions may fix some problems, but it can also create new ones, so monitor any changes closely.|
|Use information from workers||Workers are your best source of information about whether your control measures are working. Get their views – you could use focus groups, questionnaires, interviews and observation.|
|Use reports, registers and near-misses||
You can also use reports, registers and near-misses to check the effectiveness of your control measures. This could include:
1. Sleep/Wake Research Centre, School of Health Sciences, College of Health, Massey University
2. See Appendix 2 of this guidance for an explanation of ‘reasonably practicable’, or our guidance: worksafe.govt.nz
Appendix 5: Managing risk
Risks to health and safety arise from people being exposed to a hazard (a source or cause of harm).
A PCBU must first try to eliminate a risk if this is reasonably practicable. If it is not reasonably practicable to eliminate the risk, it must be minimised so far as is reasonably practicable.
A PCBU must engage with workers and their representatives:
- when identifying and assessing risks, and
- when making decisions about how to eliminate or minimise the risks using appropriate control measures.
Follow the steps below to identify, assess and manage work health and safety risks.
Step 1: Identify hazards that could give rise to work risks
With your workers, identify what could harm the health or endanger the safety of one or more workers or others (such as visitors, or bystanders).
Step 2: Assess work risks
With your workers, identify and assess the risks arising from each work hazard. Ask:
- Who might be exposed to the hazard?
- What could happen?
- How severe could the resulting injuries be?
- How could people’s health be affected?
- How likely are these consequences?
Decide which risks to deal with immediately. For example, risks with potentially significant consequences such as serious injury or death, chronic ill-health, or those with a high likelihood of occurring.
Step 3: Decide how to manage each risk
With your workers, decide how to manage work risks.
Multiple control measures may be needed to deal with a given risk. Give preference to control measures that protect many workers at the same time (for example, safety barriers, safety nets).
A PCBU can use the following hierarchy of control measures to work out the most effective control measures to use.
Appendix 6: Fatigue identification tool
Appendix 7: Extra information on fatigue, sleep and circadian rhythms
Fatigue is a physiological state where someone is unable to mentally and physically function at their best. This is caused by four main things: missing out on sleep, being awake for too long, working and sleeping in the wrong parts of the body clock cycle, and workload (mental and physical).
How to recognise fatigue
People experience fatigue differently, and may present different symptoms than other people to varying degrees. Somebody may be experiencing fatigue, but it might not be obvious from the outside.
A fatigued worker may show the following signs and symptoms, among others:
- excessive yawning or falling asleep at work
- short term memory problems and an inability to concentrate
- finding it harder to interact with other people
- poorer decision-making and judgement
- reduced hand-eye coordination or slow reflexes
- other changes in behaviour, for example repeatedly arriving late for work
- increased days off work and sick leave.
A fatigued worker may also experience symptoms that others cannot see, including:
- feeling drowsy
- blurred vision or impaired visual perception
- a need for extended sleep during days off work.
Getting enough sleep (both quality and quantity) is essential for people to be able to function at their best and stay well. Although this varies from person to person, the National Sleep Foundation* provides general recommendations for how much nightly sleep people need (within a 24 hour block), by age group. The table below shows their recommendations:
|Age range||Recommended hours of sleep|
|Newborn||0-3 months old||14-17 hours|
|Infant||4-11 months old||12-15 hours|
|Toddler||1-2 years old||11-14 hours|
|Preschooler||3-5 years old||10-13 hours|
|School age||6-13 years old||9-11 hours|
|Teen||14-17 years old||8-10 hours|
|Young adult||18-25 years old||7-9 hours|
|Older adult||65 or more years old||7-8 hours|
If people are regularly missing out on the recommended amount of sleep, they can be at higher risk of poor health and lower functioning. For shift workers, they may not get all their sleep in one block. The best quality sleep is usually obtained at night.
Missing out on enough, good quality sleep is one of the main risks of shift work. The negative effects of missing out on the recommended hours of good quality sleep build up across several days, leading to a sleep debt. The greater the sleep debt, the more likely workers are to experience negative effects, which may include falling asleep uncontrollably (microsleeps).
For the first few days, people are likely to feel sleepier and more fatigued as they miss out on more and more sleep. Other aspects of how we feel and function that are affected include:
- feeling irritable– mood swings– lower alertness
- slower reaction times– poor coordination– less effective communication
- slower thinking– less situational awareness
- less creative problem-solving.
After the first two to three nights of missing out on good quality sleep, people feel increasingly sleepy. However, with additional nights of short sleep, they may report feeling no sleepier even though their functioning is continuing to get worse. This is especially dangerous, as it means a person is less able to determine how their own functioning has changed due to missing out on sleep.
After building a sleep debt, a person needs at least two consecutive nights of unrestricted, good quality sleep for sleep structure to return to normal. A person usually achieves unrestricted night-time sleep when they go to bed and rise when they choose, and when the sleep period occurs at night. However, it may take more than two nights of unrestricted sleep after building a sleep debt before they can function at their best.
People vary in their ability to cope with shift work. Some people may find it easier to fall asleep and stay asleep at times when their body is programmed to be awake, whereas others may find this difficult to achieve. There are some personal factors that may make it more difficult for someone to cope with the disruption to their circadian rhythms, including:
- being an older adult
- already having poor sleep habits
- having poor general health and wellbeing, including stress, some medical conditions and sleep disorders (such as insomnia and sleep apnoea)
- using some medications and drugs.
Circadian rhythms are biochemical, behavioural and biological processes that occur in the body, on an approximately 24 hour cycle. Understanding how these work, including how they interact with disrupted sleep and shift work, is important. This information can help you and workers to make safe and healthy decisions regarding shift work.
People are programmed to be active and alert during daytime hours, and sleep at night. We follow this pattern because of an internal clock in the brain, called the circadian body clock. This controls daily cycles of different processes in the body, including core temperature, hormones, falling and staying asleep, moods, and ability to work. These daily cycles are called circadian rhythms.
The circadian body clock, and the circadian rhythms the clock influences, are kept in step with the 24 hour day/night cycle mainly through exposure to daylight. Meal times, interactions with other people, physical activity and work hours also play a role in keeping the circadian body clock in step with the day/night cycle. If the natural timing of the circadian body clock and circadian rhythms is disrupted, people can experience shorter, poor quality sleep, sleepiness, poor functioning and poor health.
The circadian body clock cannot fully adapt to the changes that shift work brings. As a result, circadian rhythms become out of sync with the world around us, and with each other. This disruption can result in poor sleep, poor health, and lower functioning.
The graph below shows the circadian rhythm in alertness/sleepiness over a 24 hour period, and when it is easier or more difficult to fall asleep.
The circadian body clock naturally makes people feel:
- sleepiest in the earliest hours of the morning (when they are the most error prone), and in the late afternoon
- most alert in the few hours before normal bedtime (making it difficult to fall asleep ahead of an early morning shift), and across the morning (making it difficult to fall asleep beyond lunch time, after a night shift).
This means that for shift workers, sleep is often cut short and can be of a poorer quality. The table below shows the barriers to sleep that may arise for different types of shift workers.
|Night shift workers||Sleep during the day is usually lighter and shorter than when sleeping at night. The amount of sleep a night worker will get depends on when they can get into bed after a night shift, before the circadian body clock makes them feel more alert around lunchtime/early afternoon.|
|Early starters||Sleep is cut short because early morning starts cut into the preferred sleep time. The circadian body clock makes people feel more alert in the few hours before a person’s normal bedtime, making it difficult to fall asleep earlier than usual.|
|Late finishers||Sleep may be cut short because late finishes mean that workers get into bed later than usual, but they may have to wake early for work, household, family or other commitments in the morning.|
Extended wakefulness (staying awake for a long time)
Depending on the pattern of work and sleep, shift workers may spend long periods of time awake. If a worker is able to get 8 hours of sleep per night, then they are then able to function normally for approximately 16 hours during the day. After about 16 hours of being awake, peoples’ ability to function in a safe and healthy way starts to decrease.
Workload is made up of a combination of:
- task duration (how long the work takes)
- task complexity (how difficult or easy the work is)
- task intensity (how much physical and mental effort the work demands)
- how well the person is able to meet the above demands.
When a person is fatigued, sleepiness can become more obvious during low physical or mental workload because of the lack of stimulation. High physical or mental workload may lead to fatigue, because of the effort needed to carry out the work. It can also delay and/or disturb later sleep, adding to already-present fatigue. It is important to take regular rest breaks during high workload tasks, as this can help prevent workers becoming impaired during a single work period.
Task-on-task fatigue is caused by performing mental or physical tasks, particularly difficult or high-concentration tasks, without stopping. This type of fatigue is made worse by sleep loss, and is worse during the night. As with a high workload, regular rest breaks and keeping the work period shorter can limit time-on-task fatigue increasing.
Appendix 8: Glossary