Chapter 1: Overview of Fatigue Risk Management

Learning Outcomes

On completing this chapter, you will be able to:

  • Explain reasons underlying the need for organizations to implement fatigue risk management systems.

  • Explain the limitations of prescriptive hours of work for managing fatigue-related risk.

  • Name the major components of a fatigue risk management system (FRMS).

Overview of Fatigue Risk Management

In recent years, organizations have become better at managing workplace risks including issues such as materials handling, use of seatbelts and safety harnesses, as well as exposure to harmful chemicals. As these risks have been reduced, other threats have become more apparent. This is particularly true of fatigue, which until recently was not well understood or easy to measure. Recent research and applied management strategies are beginning to provide solutions for individual employees and organizations to better manage fatigue-related risk. This chapter of the guide provides information about managing fatigue-related risk within a safety management system (SMS) framework. This incorporates a formal risk assessment and will likely fit within existing organizational safety management structures. The rationale for the development of a fatigue risk management system is also provided in this chapter.

Causes and Consequences of Fatigue

Fatigue is an experience of physical and/or mental tiredness that results in reduced alertness and negatively impacts performance. The major cause of fatigue is not having obtained adequate rest or recovery from previous activities. In simple terms, fatigue largely results from inadequate quantity or quality of sleep. As discussed in Fatigue Management Strategies for Employees, there are many consequences of fatigue and they fall into three major categories – physical (e.g., abruptly nodding off for a few seconds, called a microsleep), mental (e.g., lapses in attention) and emotional (e.g., irritability). The fatigue associated with tiredness and reduced alertness is different from physical fatigue or weariness that is caused by long and/or hard physical work. In this case, fatigue may be more accurately defined as mental fatigue although it certainly affects physical performance as well – especially tasks that require mentalphysical interactions like hand-eye coordination, reaction time, and fine motor skills. Other skills that are impaired by fatigue include attention, vigilance, concentration, ability to communicate information clearly and accurately, and decision-making. Impairment can lead to fatigue-related errors, which in turn can lead to incidents or accidents. Evidence from industrial and government investigations as well as industrial risk data demonstrates that fatigue and sleepiness are major contributors to incidents and accidents across the entire transportation industry. Incidents and accidents that result from fatigue can be severe and may include fatalities but are most often associated with employee injury and/or equipment damage.

Managing Fatigue Levels

An understanding of both the causes and consequences of fatigue enables us to design more effective systems to manage fatigue-related risk. Fatigue is sometimes managed indirectly by organizations (and regulators) through prescriptive limits on work hours, often because it is seen as the only available option. There is an assumption that prescribing maximum limits for the length of work shifts and minimum thresholds for breaks between shifts ensures that employees achieve adequate rest and recovery. This assumption most likely evolved from information about the way in which humans recover from physical fatigue. Physical fatigue accumulates and diminishes in a predictable way over time, as shown in the figure below.


The manner in which physical fatigue accumulates and dissipates in relation to work and rest
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The manner in which physical fatigue accumulates and dissipates in relation to work and rest

Based on this assumption, the management of physical fatigue by limiting work hours and managing break periods is logical and practical. However, the same may not be assumed for mental fatigue. Common approaches for managing this type of fatigue often assume that the factors that cause mental fatigue are similar to those that cause physical fatigue. And while it is true that mental fatigue does, in part, increase in a relatively predictable way over time during waking hours and dissipate over a period of recovery, time is not the only factor that needs to be considered. The most important factors affecting mental fatigue levels are:

  • Sleep quantity and quality – insufficient or poor quality sleep results in increased fatigue levels. This is because both how much and how well one sleeps are important for recovery from fatigue and for maintaining normal alertness and performance. This applies not only to a single sleep period, but to consecutive sleep periods. If an individual gets inadequate sleep (quality or quantity) over a series of nights, this also causes increased fatigue.

  • Time awake – how long an individual is awake affects fatigue levels. Research indicates that alertness and performance levels begin to decrease after a certain number of hours awake.

  • Circadian rhythms – fatigue levels are also affected by the time of day. For example, fatigue can be a bigger problem in the early hours of the morning

It is not correct to assume that a given break from work will provide a given level of recovery; the length of the break is not the key factor. It is the amount and quality of sleep obtained in the period of time away from work that determines recovery from fatigue. The timing of a work period within the 24-hour day will also determine fatigue risk.

Both work and non-work factors can affect sleep. Work-related factors – length of shifts, the type of work being performed, workload, work environment (e.g., heat, humidity, noise, vibration, lighting levels) and breaks within a shift – can all influence the amount of sleep and time awake obtained in a 24-hour period.

Non work-related factors – sleep disorders, family responsibilities, social and leisure engagements, and emotional stress – can all affect the amount and quality of sleep people obtain. These factors can also affect the length of time individuals are awake, which can also affect fatigue. The figure below shows the relationship between each of these factors.

The relationship between sleep, time awake, circadian rhythms, and fatigue, as well as the effect of work and non-work factors on sleep and time awake.
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The relationship between sleep, time awake, circadian rhythms, and fatigue, as well as the effect of work and non-work factors on sleep and time awake.

With all of the contributing factors in mind, it is easy to understand why prescriptive limits on work hours may not, on their own, be adequate for managing fatigue-related risk. Prescriptive limitations on shift length generally assume that a break of a given length has a predictable recovery value; for example, that a 10-hour break will allow the same recovery to take place regardless of when the break occurs. While this may be relatively true for physical fatigue, it is definitely not the case for mental fatigue. Providing the same time off during the day, as opposed to night, may result in less recovery due to the effect on sleep. Factors such as this must be taken into account when developing an FRMS.

The FRMS should be embedded within the existing SMS framework to allow fatigue to be managed within existing organizational safety structures. This also ensures that responsibility for managing fatigue risk is shared between employer and employee. It may also allow safety professionals or other stakeholders in the company to develop a cost-effective FRMS without needing to call in outside fatigue expertise. However, it is important to have an understanding and appreciation of fatigue-related risk within a workplace.The figure below illustrates how fatigue can be incorporated into an overarching SMS.

Fatigue risk management systems work best within the framework of a larger safety management system.
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Fatigue risk management systems work best within the framework of a larger safety management system.


An incident trajectory demonstrates how weaknesses or "holes" in management systems can provide opportunity for incidents
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An incident trajectory demonstrates how weaknesses or "holes" in management systems can provide opportunity for incidents

A Risk-Based Approach

Managing fatigue-related risk under an SMS framework involves developing comprehensive defences against the hazard of fatigue based on a formal assessment of risk. Organizations can decide to do as much or as little as necessary to manage their own levels of risk.

An important theorist in the area of organizational risk management, James Reason, describes the "normal" environment in organizations that generally precedes a workplace incident. Reason suggests that there is no 100% effective safety control for any hazard (such as fatigue). The inherent weaknesses or "holes" in a given safety defence provide opportunities for incident "trajectories" – the series of events and conditions leading to an incident – to penetrate the defence.

An effective safety management system or, in this case, fatigue risk management system, should use multiple, overlapping, and redundant defences against a given hazard. In a multi-layered system, an incident can only occur when all the defensive systems fail. That is, in circumstances where the incident trajectory passes through the holes in each of the defensive layers. The effectiveness of the safety management system can therefore be improved by (1) the appropriate selection of supplementary layers, and/or (2) strengthening individual layers (shrinking the holes).

Reason's principles for the development of an SMS can be easily applied to a fatigue risk management system. The figure below shows a hazard control diagram for fatigue. Vulnerabilities along the fatigue-related incident trajectory should be identified so that supplementary defensive layers can be introduced and/or existing defensive layers can be strengthened. Investigating incidents also ensures that appropriate hazard controls are put in place at each level of potential risk.

In general, fatigue has traditionally been managed using a single layer of defence (i.e., limits on work hours). The assumption is that compliance with the limits on working hours is evidence that an employee is adequately rested and fit for work and will not make any fatiguerelated errors. This may not always be the case. Without supplementary defensive layers it is entirely possible for an employee to comply with working hour limits but to be too tired to work safely (e.g., had a 12-hour break from work but didn't get enough sleep due to a sick child or a night out on the town). Each of the five levels of control is discussed in separate chapters, but a brief description of the theory is provided below.

Hazard-Control Model for Fatigue Risk Management
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Hazard-Control Model for Fatigue Risk Management

The hazard control model illustrated in the figure above shows the controls in place for reducing fatigue-related risk. In theory, if each level of control is in place, the “holes” in the management system along the incident trajectory should become smaller, minimizing the likelihood of a fatigue-related incident.

Briefly, a fatigue-related incident is preceded by a fatigue-related error. In turn, a fatigue-related error is generally preceded by fatigue-related behaviours. Fatiguerelated behaviours or symptoms in turn indicate that an employee has either not had adequate sleep (not enough or not enough good sleep), or has been awake for an excessive period of time. Finally, inadequate sleep or excessive time awake may occur as a result of inadequate sleep opportunity (i.e., too short a break between work shifts).

There are five major levels of control for managing fatigue risk:

  • Level 1 (organizational): making sure scheduling gives employees adequate opportunity to sleep

  • Level 2 (individual): making sure employees actually get sufficient sleep

  • Level 3 (behavioural): monitoring for symptoms that indicate employees are fatigued

  • Level 4 (error): stategies to ensure that fatigue in the workplace does not result in errors or incidents

  • Level 5 incident: determining the role of fatigue in workplace errors or incidents

A successful fatigue risk management system addresses each of these levels by organizing defence systems around these layers. Most fatigue countermeasures (either formal or informal) can be assigned to one of the five defensive layers.

The FRMS should be developed and implemented using a risk-based approach. Organizations should determine the specific level of fatigue-related risk associated with their operations. Organizational risk should be assessed in terms of the type of work being conducted as well as the environment in which the work takes place. After identifying highrisk areas for fatigue within the workplace (by work group or by specific tasks), systems can be put in place to either reduce or eliminate fatigue through processes such as schedule reform (fatigue reduction) or through the implementation of mitigating strategies such as napping and task rotation (fatigue proofing).

Implementation Map
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Implementation Map

The figure above provides a plan, or roadmap, for organizations implementing an FRMS. The individual components of an FRMS are designed to complement each other to ensure the best possible outcomes for fatigue risk management and safety. This guide details each of the components recommended for an effective FRMS, and provides information on the relevant implementation process. No single component should be considered more important than another – all components should be examined and integrated into the FRMS to achieve the ultimate goal of safety.

An FRMS Working Group

The design, implementation, and day-today operation of any management system require structure and leadership. A working group should be formed to assume responsibility for the FRMS in the organization. In smaller operations, the role of a working group may be performed by one or two employees – the size and makeup of the group will be dictated by the level of fatigue-related risk the organization carries and the size of the organization itself. It is also possible that an existing safety-oriented committee could take on the role of the FRMS working group.

The working group is responsible for the design, implementation, and ongoing review of the FRMS. The working group should be composed of a representative sample of employees likely to be affected by the FRMS. Ideally, it also includes management and operational personnel.

This increases the range of opinions and ensures that information is received from all levels of the organization. Working group members should also have the opportunity to consult with other operational personnel, bringing an even wider range of perspectives to the process of FRMS design, implementation, and review. This is best achieved through twoway communication of program objectives, milestones, progress, and the involvement of all employees in the development and review processes.

Working Group Training

Members of the working group may require some training about the causes and consequences of fatigue and how to manage the risks. Training for the working group should:

  • outline fatigue, its associated risks, and management strategies at the individual level

  • provide strategic information on the daily management of fatigue from an organizational perspective

  • detail effective FRMS design and implementation processes

  • provide information about how to evaluate and audit the FRMS over time.

This type of training can be obtained from Fatigue Management Strategies for Employees (TP 14573E) and this guide. Further reading on these issues can be found in the list of resources included at the end of this guide.

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