52ND ANNUAL CONFERENCE, Bali, Indonesia, 24-28 April 2013
WP No. 159
Fatigue Risk Management Systems
Presented by PLC
This paper provides an analysis of (recent) scientific findings on fatigue (without taking individual situations in consideration) and the risks resulting from fatigue. The paper comments on the ways of mitigating the risks by introduction of risk management systems designed to address and mitigate fatigue risks in general. The aim is to find recommendations and guidance on the adoption of Fatigue Risk Management Systems (FRMS) additions in accordance.
In this paper the completeness of the policies of ICAO and IFATCA concerning fatigue related management systems have been evaluated. The evaluation is done by comparison to a theoretical FRMS elements model as drafted in this paper. In order to establish the theoretical FRMS elements model, a study has been performed based on technical and scientific literature. The FRMS elements model is based on the conclusions in the reviewed literature.
The evaluation of the policies of ICAO and IFATCA show that these are not complete in terms of the advised elements of a FRMS. Whereas ICAO policy focusses solely on the flight crew and the issues that are faced in that part of the operations, IFATCA’s policies do not specifically detail a FRMS, although some elements of the advised FRMS are mentioned.
It is the conclusion of this paper that current policies do not provide an applicable, complete overview of a FRMS. The inclusion of the FRMS elements Model as established in this paper in the IFATCA Professional and Technical Handbook is therefore advised.
The FRMS elements model can be summarized as follows:
The prerequisites in the FRMS elements model should be embedded in the organization, whereas the tools are active management tools to influence the fatigue build-up and with that the fatigue related risk development.
1.1 Task and relevance of this paper
During the IFATCA conference in April 2011 PLC was tasked to write a paper on Fatigue and on Fatigue Risk Management Systems (FRMS). This paper elaborates on recent research on fatigue and on how this could be interpreted in a model. This paper also provides guidance on the best practice of a FRMS and explains what it is, what it consists of and how it is set up.
At the moment fatigue issues are a subject of attention in aviation. In the US multiple incidents happened in 2011 when at different airports, air traffic controllers fell asleep on duty. These incidents received a lot of attention in the international press and became a highly scrutinized public concern.
Currently conclusions from numerous studies in the field of fatigue, fatigue risks and fatigue management are already available as well as the associated literature. These studies are performed on fatigue issues in general, in other sectors and in the transport sector; all the studies relate to the assessment of the issue and the determination of the actions to be taken.
ICAO has stressed the importance of a FRMS by publishing the Fatigue Risk Management Systems Manual for Regulators (Doc 9966) in 2011. This manual provides guidance on the development, implementation, approval and monitoring of a FRMS.
ICAO Annex 6, Part I added Appendix 8 in December 2011. This Appendix describes the Fatigue Risk Management System Requirements. Although this manual is for flight and cabin crew members, a lot of the information could well be applicable for personnel providing ATC services.
The following sub questions were taken into account resulting in a conclusion on how FRMS can be addressed:
- ‘What can we learn when we compare (current) scientific knowledge on fatigue?’
- ‘What can we learn from (current) scientific findings to mitigate the effects of fatigue on safety critical staff?’
- ‘What can we learn when we compare science to current regulation regarding fatigue?’
- ‘How is a FRMS built up, what are its main elements based on scientific knowledge and applied FRMS in other fields of operation (air crew, road, water, railway)?‘
- ‘Can we use ICAO / IFATCA policies on FRMS as guidelines?’
This will lead into a recommendation for MAs how to address fatigue related risks in their own FRMS.
This paper addresses the outcome of scientific research on fatigue from referred documentation, extracts an empirical model from this research with the FRMS elements and compares this model with current regulation and policy regarding fatigue and FRMS. The following model shows a visual indication of this approach.
The paper contains a comparison of a selection of available scientific studies concerning fatigue. For analysis purposes we have narrowed down these studies in three fields of attention, relevant to the task:
- What is determined about the cause of fatigue?
- What is the effect of fatigue, in terms of risks?
- Ways to mitigate fatigue risks
This results in elements which should be included in a FRMS.
In this paper the scope of the task is limited to the following areas of attention:
A broad range of scientific literature is reviewed. In the approach we started with literature reviews and consecutively zoomed in on literature on specific elements of fatigue and FRMS. This paper will conclude on a high level of the advised composition of a FRMS: The more in depth composition of the individual elements will not be discussed in this paper.
This paper does not provide a comparison between adopted regulation on FRMS within individual states. This paper abstracts from the effect of drugs or illness on fatigue.
1.5 Outline/Report structure
To derive the outcome of the task, the paragraphs are organised in the following structure:
Paragraph 1: Introduction, task and relevance, objectives, approach and scope.
Paragraph 2: Discussion and study, literature review and opinion on scientific findings resulting in a theoretical FRMS elements model.
Paragraph 3: Comparison to current ICAO and IFATCA policy.
Paragraph 4: Conclusions and recommendations.
Many argue that fatigue is an increasing health and safety problem in our daily lives due to the so-called 24-h society with round-the clock operations. Life expectancy, global communication result in decreasing emphasis on the need for sleep, and the nature of work has changed to comprise more sustained attention and monitoring tasks.
There is compelling evidence that fatigue compromises safety, and that fatigue and its causes need to be managed carefully (Williamson et al, 2009).The basic goal for managing fatigue is safety, as fatigue is a hazard that must be managed comprehensively. Safety management is about safety of the individual and safety of the overall system operation. Fatigue management in ATC, for all the complexities, can be seen as simply as respect for the known basic human performance limitations. (Shallies, 2011)) Without a holistic approach, fatigue will degrade individual performance and pose a threat to safety (Shallies, 2011 and Brathwaite, 2012).
2.2 Fatigue related incidents and their causes
In 2011 at least seven incidents happened in the US where an air traffic controller fell asleep during a midnight shift. These incidents prompted negotiations between the government and the controllers’ union to change the way controllers are scheduled to work. The Federal Aviation Administration (FAA) acknowledged that there was a widespread problem with fatigue among controllers and that the organization instituted changes in work schedules. Two of the new rules established in the agreement are more time off between shifts (minimal 9 hours) to allow for appropriate rest and longer mandatory rest periods. Two other rules are allowing controllers to listen to the radio and read appropriate printed material while on duty during the hours of 10 p.m. and 6 a.m., as traffic permits. It also allows controllers to request a leave of absence if they are too fatigued to work.
The agreement reinforces existing FAA policy that prohibits air traffic controllers from sleeping while performing assigned duties. The FAA will continue to provide controllers breaks on midnight shift based on staffing and workload. Controllers on break will still be expected to “conduct themselves professionally and be available for recall at all times,” the FAA said in written statement.
In contrary to FAA policy, a fatigue study by FAA and the National Air Traffic Controllers Association resulted in understanding the following; scheduling of air traffic controllers often does not give them time to adjust to any one set of waking and sleeping hours. Often they will work a week of midnight shifts, then a week of morning shifts, then a week of swing shifts beginning in the afternoon — such changes can take an exhausting toll on the body and mind. The chief in charge of the study recommends that controllers be allowed sleeping breaks of as long as 2.5 hours during mid-night shifts.
Other fatigue experts concur that Air Traffic Controllers often bounce from morning shifts, to afternoon, to night shifts, leaving little time for the body to adjust. Fatigue experts like Philip Gehrman, director of the Behaviour Sleep Program at the University of Pennsylvania, said it is crucial that their shifts remain more constant. “It would be nice if there were a greater appreciation that our bodies have a limit – we’re not equally able to function at all hours of a 24-hour day,” Gehrman said.
Is Fatigue management just a problem of revised work rules and rosters or do we (also) need to approach this problem from another angle?
2.3 Definition of fatigue
There are many definitions of fatigue to be found, for this paper we thought to find a definition that is most tangible, to the point and specific for the aviation industry. For this reason, to keep the discussion clear, in this document we base ourselves on the same definition as ICAO for fatigue:
‘A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity) that can impair a crew member’s alertness and ability to safely operate an aircraft or perform safety related duties.’ (ICAO FRMS Manual for Regulators, Doc 9966, 2011)
When we look at this definition we see that the state of fatigue is determined by physiology, has effects on both mental as physical performance. The state is determined by sleep loss, extended wakefulness, the circadian phase (explained below under causes of fatigue) and workload. It mentions that the ability to perform safety related duties is impaired.
The definition does not relate to the personal (subjective) effects of these variables and the definition relates to aircraft crew. For this reason the definition used in this document will be defined as follows:
Fatigue: A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity), affecting the subjective state, that can impair an air traffic controller’s alertness and ability to perform safety related duties.’
The level of fatigue of a person can be measured in various ways by measuring physical effect. For this paper however the methods of establishing the level of fatigue is not under review as it will have no effect on the FRMS elements (rather on the determination of fatigue than on the management thereof).
2.4 Causes of fatigue
Fatigue is a normal physiological effect related to your everyday routine. There is a physiological system defined that influences the level of fatigue (physiological state) that a person experiences. This system is called the circadian rhythm (Halberg et al, 2003, Akerstedt, Folkard and Portin, 2004, see also the framework below).
Fatigue is largely determined by the combined influence of the duration of sleep/wakefulness and the circadian rhythm (Williamson et al, 2009, London Department for Transport, 2010). The circadian rhythm in sleep is the result of a pattern of increasing and decreasing sleepiness across a roughly 24-hour period, with the highest level of sleepiness occurring in the early morning between around 02:00 and 06:00 when the urge to sleep is the strongest. The lowest levels of sleepiness occur around mid-morning and in the evening between around 20:00 and 22:00.
The more activities planned out of phase with your circadian rhythm, the more effect the work will have on your physiological state; fatigue will arise earlier when performing duties outside of your personal circadian rhythm (e.g. sleeping during the day and awake during the night) (Di Milia et al, 2009).
Influences on alertness: Circadian rhythm and the homeostatic factor
A number of studies (Akerstedt, Folkard and Portin, 2004) involving normal night time sleep, sleep deprivation, spontaneous desynchronization, and forced desynchronization have shown that alertness and performance display a time of day pattern with a maximum in the late afternoon and a trough in the early morning around 05:00. This pattern is known as the circadian rhythm. Based on this pattern the three process model of alertness was drafted.
The figure below shows the components of the Three Process Model of Alertness.
Process C: sleepiness due to circadian influences and has a sinusoidal form with an afternoon peak.
Process S: exponential function representing the time since awakening and, therefore, is highest on awakening (in the graph at 6 AM), with an initially steep rate of drop declining toward its lower asymptote over the course of the waking period. At sleep onset, process S is reversed and called S’ and recovery occurs in an exponential fashion that initially increases very rapidly but subsequently levels off toward an upper asymptote. Total recovery is usually accomplished in 8h.
The components of the Three Process Model of Alertness (Ref. 4)
NOTE: The time period between around 20:00 and 22:00 is known as the ‘forbidden sleep zone’ because at this time the alertness level in circadian rhythm is high. It can also be difficult to sleep at this time of the evening due to social and domestic pressures (London Department for Transport, 2010).
As mentioned above besides the circadian rhythm (C in the graph above), the ‘Time since sleep’ (TSS) variable also effects the level of alertness of a person (Akerstedt, Folkard and Portin, 2004, Cabon, 2011). The following graph shows the effect of TSS on the general alertness level. This effect is called the homeostatic factor and is associated with the amount of ‘prior wake’ and amount of ‘prior sleep’, process P in the graph below:
Process W (waking) reflects sleep inertia, i.e. “a transitional state of lowered arousal occurring immediately after awakening from sleep and producing a temporary decrement in subsequent performance”. Process W is also an important factor to be considered as it might have a safety impact when considering napping during duties. (Van Dongen, 2004)
These models predict that two conditions impact the alertness level, the circadian factor and the homeostatic factor. Under some circumstances, only one condition is met, e.g. during daytime sleep after a night duty, the sleep pressure is maximum but the timing is not appropriate, leading to a disturbed and shortened sleep and thus a disturbed recovery. The effects combined lead to the presented graph S+C in the graphs above in the condition that the subject awakes at 6 AM.
These important factors have to be kept in mind when considering the effects of rostering of ATCOs.
Apart from the circadian rhythm and the TSSs, other factors can cause fatigue or loss of alertness. The multiple causes of fatigue can be divided into different categories, being: work-related factors, environmental factors and individual/personal factors.
These factors can be found in the outcome of scientific research. Causes for each category of factors will be described in random order below.
2.4.1 Work-related factors
The factors that influence fatigue are amongst others, those that relate to the nature of the work and the working arrangements; (Canada tripartite steering committee on ATC fatigue, 2001, Parkes, 2004, Di Milia et al, 2009, Williamson et al, 2009)
- Shift scheduling. Including regular hours of work and shift cycles, specific shift patterns (fixed or rotating (Alteration of the circadian time-keeping system and physiology of sleep homeostasis often results in fatigue)), irregular shifts, e.g. rotating shift-and night-work schedules (disrupt the circadian system), speed of shift rotation, starting time of shift/work, rest periods/breaks, number of off-days, the regularity of shift schedules, reserve duty.
- Night shifts. Permanent nightshifts have an elevated risk of metabolic syndrome-type medical conditions, circadian system de-synchronisation, and associated sleep disruption and fatigue.
- Time on task. (hours of consecutive work, cumulative hours worked over days, consecutive number of days worked including overtime)
- Overtime can reduce the available recovery time (timing of the shifts and the temporal placement of the overtime). Current shortage of ATC staff can increase the need for overtime to maintain service levels.
- Workload (the intensity of work while on position both subjective and objective), the level of challenge in the work (boring/monotonous work (lack of stimulation) (see note). Periods of low workload can negatively influence alertness of individuals whose performance may already be degraded by fatigue.
- Job control/autonomy.
Note: (Eurocontrol, Managing shiftwork in European ATM, 2006): ATC systems evolve every day to be more technology dependent. This increases the level of automation, reduces the level of actions and could lead to boredom, which in turn could reduce alertness), traffic levels, complexity, operations that require sustained vigilance and physical and mental workload/work of that day and that week.
2.4.2 Environmental factors
Related to work factors are the environmental factors which affect the fatigue level of a person; (Kronauer, Forger and Jewett, 1999, Canada tripartite steering committee on ATC fatigue, 2001, London Department for Transport, 2010)
- Ambient work conditions (e.g. stressful temperature, noise, vibration, chemical exposure, air quality, light (e.g. brighter lighting improves alertness, especially at night).
- Physical workplace parameters and conditions (e.g. physical atmosphere).
2.4.3 Individual/personal factors
Apart from work related factors, factors from the life outside work play a role in the fatigue level of a person; (Canada tripartite steering committee on ATC fatigue, 2001, Halberg et al, 2003, Parkes, 2004, Di Milia et al, 2009, London Department for Transport, 2010)
- Personal circadian rhythm; this is affected by the ATCO’s age, sex, race (sleep duration varies by race), societal, family, and various environmental (e.g. light exposure) influences. This is also called the circadian chronotype. Individuals differ in terms of the time of day of their peak alertness and sleepiness (morning or evening types).
- Duration of wakefulness and time awake (time in hours since last sleep).
- Quantity and quality of (prior) sleep, sleep requirement (versus sleep obtained) and sleep debt. Sleep loss is cumulative; repeated day-to-day sleep loss results in the accumulation of sleep dept. The greater the sleep debt, the greater the level of fatigue. Employees working and sleeping out of phase with their circadian rhythms gradually accumulate sleep debt which will lead to fatigue.
- Mental exertion in proportion to the relative fitness (both physical and mental) at commencement of the work shift. Each consecutive year working in irregular shifts (regardless age) reduces the mental ability of a person.
- Personal demographics (e.g. age, commuting times and gender), psychosocial milieu.Age; Aging seems to result in a gradual deterioration and more difficult adjustment of the mechanisms that support the physiological, circadian, and sleep systems. Due to the aging process various factors affect the recovery from fatigue and the flexibility in the ability to cope with disturbances of the circadian system. Furthermore Aging increases the tendency to morningness, advancing the circadian phase position up to 2 hours.Deterioration of the biological systems begins from about the age of 45-50 years. E.g. altering eyesight (diminished visual acuity, narrowed peripheral vision, and cataracts), slower speed of perception and response to stimuli, and reduced muscle strength. Commuting time and type (transport); commuting time can be an important determinant of sleep duration (short(er) recuperative sleep and excessive daytime sleepiness). Also the length of the commute to and from work can appreciably add to the demands of the work day.
- Lifestyle issues, partner/marital status, off-duty activities, household/social issues (e.g. dependency care (childcare responsibilities, family members)) disturbed socio- temporal patterns (resulting from atypical work hours leading to family problems, reduced social support, and stress).
2.4.4 Health factors
All these causes interact in a complex manner on the physiological state and have their effect on the level of fatigue. Apart from these three main factors, health factors also play a role in the physiological state of a person, such as (Parkes, 2004, Sirois, 2009, Di Milia et al, 2009, London Department for Transport, 2010):
a. Medical sleep disorder problems, medication use.
b. Physical and mental health status, underlying health issues (e.g. hypertension, diabetes, epilepsy, gastrointestinal complaints, cardiovascular disease, cancer, pregnancy and reproductive disorder, etc.) disturbed metabolic and other pathophysiological systems.
c. Improper timing and content of food (i.e. building cardiac risk factors, digestive disorders), diet, nutritional status.
d. Use/abuse of coping substances (e.g. cigarettes, caffeine, sleeping pills, alcohol, drugs, etc.).
Related to circadian rhythm is a sleep disorder known as the shift work sleep disorder (SWSD). The exact prevalence is unknown, but the disorder is probably uncommon, representing a small proportion (5% to 10%) of patients presenting to sleep disorders centres with the complaint of insomnia. For this reason this disorder related to shift work for the purpose of this paper is regarded as an illness (American Academy of Sleep Medicine in association with the European Sleep Research Society, Japanese Society of Sleep Research, Latin American Sleep Society, 2001, FNV bondgenoten, 2012). Sleep disorders can disrupt both the quantity and quality of sleep, leading to both chronic and acute sleep loss (Williamson et al, 2009).
2.4.5. Effects of nightshifts
With regards to the effects of nightshifts the following summarization can be made (Eurocontrol, Managing shiftwork in European ATM, 2006). The effects on fatigue and health of the ATCO are mentioned. Other effects (social e.g.) are not mentioned. Night shifts increase de-synchronisation and fatigue and therefore can lead to:
- Disrupted rhythm of sleep and activity (working against the body clock)
- Reduced physiological preparedness to perform
- Daily variations of body temperature
- Impaired well-being (increased tiredness)
- Decreased motivation and capability to work (extension of reaction times)
- Loss of productivity and efficiency (this is lower between 7 pm and 7 am and there is a massive dip between 10 pm and 6 am with a trough at 3 am)
- Experienced feelings of under load (low workload at night induces fatigue and stress resulting from efforts to counter boredom**)
- Experienced feelings of overload (high workload meets reduced staff)
It is advised that these effects are taken into consideration when preparing a working schedule.
** Note: Taking a break is very important during night shifts since either low traffic levels induce fatigue resulting from efforts to counter boredom or, high traffic load is prevalent, and both conditions meet the de-synchronisation of the body clock.
2.4.6 Conclusion on causes of fatigue
As can be seen from this summarisation on the causes of fatigue, it is clear that the causes are wide-ranging, meaning that management of fatigue needs to address a broad spectrum of factors in order to be effective.
2.5 The effects of fatigue
Since 1993 over 14 accidents resulting in 263 fatalities had fatigue as a causal or contributing factor (Gimbrere, 2011). Until now the focus has been on pilot fatigue, however the well-being of an air traffic controller is no less important.
We consider that fatigue may take several forms including sleepiness as well as mental, physical and/or muscular fatigue depending on the nature of its cause. All forms of fatigue can result in impaired human performance capabilities and a latent threat to safety due to slowed or incorrect responses and/or total failures to respond. Under certain circumstances, degraded performance can contribute to an incident, accident or other occurrence (Canada tripartite steering committee on ATC fatigue, 2001, Williamson et al, 2009).
The impacts of fatigue to individual performance can be numerous: from loss of situational awareness, loss of attentiveness, impaired judgment, an increased risk of operational errors, to a degradation of accuracy and timing, as you experience involuntary micro/sleeps and a subjective feeling of drowsiness or tiredness as your attention wanes, to an overall decline in performance, cognitive functions to ultimately reduced safety (Dawson and McCullough, 2004, London Department for Transport, 2010, Gimbrere, 2011) Accordingly, governments and safety professionals have argued that mental fatigue is an identifiable work place hazard that warrants regulatory attention (Dawson and McCullough, 2004).
Besides these effects fatigue increases the desire to obtain sleep. This effect is magnified during circadian lows, which are encountered by people who normally sleep at night and work during the day (diurnal). Circadian lows are periods of high fatigue and poor performance. The highest levels of fatigue and worst performance occur when circadian rhythms dictate sleep. Midnight shifts have the most impact on the circadian rhythm (more disruptive than other shift patterns) and are generally the most difficult shifts to adapt to in terms of fatigue management, as the body’s natural tendency towards sleep increases over these hours. More than two consecutive midnight shifts have a cumulative impact and the longer the shift lasts and the earlier the shift starts, the greater the disruption to circadian rhythms. The ability to obtain rest before and after midnight shifts is a major factor in the management of fatigue, the start and end times of the shift must be considered as well as the overall length of the shift (Canada tripartite steering committee on ATC fatigue, 2001, Transportation Safety Board of Canada, 2011)
The result of the development of fatigue and sleepiness may be either a safe recovery or a decrease in performance capability which may lead to an adverse safety outcome. In the model below, the effects of the main influences noted to increase fatigue (which include work related factors, environmental factors, personal factors, health factors and circadian rhythm influences) are shown on the left-hand side. The model conceptualizes the experience of the starting condition and the increase of fatigue, providing the drive for restorative rest and sleep (or safe recovery, as shown on the right-hand side of the model). To the extent that this drive remains unsatisfied, the capacity to perform will be impaired and this in turn will increase the risk of adverse safety outcomes. Increasing levels of fatigue and sleepiness decrease performance capacity with, of course, falling asleep having the most extreme effects on performance capacity.
Error rates increase exponentially with an increase of fatigue; Errors are broadly comparable in nature and frequency with other forms of impairment (e.g. alcohol intoxication) (Dawson and McCullough, 2004, UK CAA, 2007, London Department for Transport, 2010).
Chronic sleep loss can be a risk factor in a range of serious illnesses. Sleep loss has been shown to be a risk factor for obesity and diabetes, while shiftwork has been shown to increase the risk of gastrointestinal problems. Research has also suggested a possible link between the circadian disruption associated with night shiftwork and an increased risk of cancer (London Department for Transport, 2010).
2.6 Theoretical tools of fatigue mitigation
In the studied literature a number of practical to theoretical measures are referred to, aiming to mitigate the risks of fatigue. The most tangible measures are discussed below, followed by assessed pros and cons and the opinion on the measure in terms of sufficiency and practicality.
2.6.1 Tool 1: Breaks
The effect of breaks has been studied in various researches. Although breaks as shown in the literature do not provide a complete answer to the fatigue risk, it can be one of the tools used to mitigate fatigue in a FRMS. Strategic use of breaks has an impact on the level of alertness, as hours of consecutive work is one of the variables shown in the fatigue factors (see paragraph 2.4.1). The following can be derived from the literature:
Taking a break from activity is a short-term countermeasure against mental and physical fatigue (London Department for Transport, 2010, Transportation Safety Board of Canada, 2011). The established norm is two hours on position followed by a relief break. This applies when handling complex and busy air traffic (breaks need to be frequent as a higher workload is concerned). This period may be extended to four hours (but should not exceed) in the case of a low workload and subject to other employed mitigating measures. A meaningful break means that the individual is not responsible for an operating position. The minimum duration of a break should be 10 minutes plus 10 minutes per hour of work. Breaks should allow napping (typically 20 to 40 minutes) with ample time (20 minutes) to overcome subsequent sleep inertia (period of grogginess experienced upon waking). (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006, Baumgartner (ATM/HLG5), 2012).
Studies show it is important to control the amount of sleep during controlled rest breaks. (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006, UK CAA, 2007, Transportation Safety Board of Canada, 2011, Gimbrere, 2011, Anthony, 2011, Braithwaite, 2012) Napping is a countermeasure to fatigue, it can increase productivity, creativity and problem-solving skills. The ability to sleep/nap during midnight shifts has been found to reduce the level of performance degradation experienced by controllers working these shifts. When only limited time is available, study shows that the best reaction times were demonstrated after naps of 20 minutes maximum. This may be a direct result of awakening from slow–wave sleep in the longer nap condition (sleep inertia). When more time is available a recuperative break of up to 2.5 hours is advised during the midnight shift (Gimbrere, 2011). Napping is considered the only effective countermeasure for sleep deprivation (Eurocontrol, Managing shiftwork in European ATM, 2006,). Therefore, strategic and prophylactic naps are suggested as very effective at maintaining alertness during circadian rhythm troughs, as well as under conditions of sleep loss. Ten to twelve minute ‘power naps’ can refresh for a short period of time. Napping is considered part of a duty period and should not extend it.
In order to implement this tool, duty rosters management must provide relief controllers, adapted rest periods and sufficient break periods for controllers to maintain their daily eating habits regardless of which shift they are working. It is highly recommended that physical arrangements (e.g. rest rooms, beds) and sufficient break periods are provided to allow for strategic naps during night shift (Brathwaite, 2012).
- Breaks are easy to implement, given a sufficient staffing level
- Can be easily combined with a broad spectrum of measures to improve alertness and fatigue level
- Naps can be combined with regular breaks
- Possibly extra resources needed (relief controllers)
- Managing how ATCOs spend their break requires a specific culture
- There is a risk to restorative naps, especially when they last over the advised 20 minutes: Sleeping is linked to sleep inertia, which results in a dramatic reduction of alertness for the first 15 minutes after the nap (Cabon, 2011)
- It is not a complete solution to the fatigue risk
- Provisions must be arranged to implement naps
2.6.2 Tool 2: Hours of Service (HOS) model
One of the earliest methods of managing fatigue and alertness level consists of the management of hours of service. The model was created in the 1950s following the earliest circadian findings (Halberg, 2003). An hours of service model consists of a guideline which determines that a shift, in terms of hours, cannot exceed a specifically set maximum, often set at 8 hours.
The reviewed literature indicates that there is an increased probability of degraded performance when prolonged consecutive hours are worked. Literature indicates that the potential exists of a significant level of performance degradation for persons working in excess of 10 consecutive hours (rather then 8). It is advised that, when using a HOS model, a prescriptive approach is implemented to ensure that conditions which degrade human performance are not unwittingly introduced into the operations. Nowadays scheduling design in which HOS is implemented can be supported and improved by the use of specific software (Canada tripartite steering committee on ATC fatigue 2001, London Department for Transport, 2010, ICAO FRMS Manual for Regulators, Doc 9966, 2011).
With regards to the number of hours worked it is determined that the individual health and performance decreases with shift duration beyond eight hours. The probability of errors increases exponentially after this time. The studies reviewed in this document also indicate that the number of successive shifts, the time on position, night work, and shift rotation affect performance and thereby bear certain risks. Incidentally the length of a shift may exceed the 8 hours with a maximum of 10 hours per day (depending on the type of shift). However over a longer period of time the average of 8 hours per working day should not be exceeded (Eurocontrol, Managing shiftwork in European ATM, 2006)
While HOS is a broadly used tool in the management of fatigue, Dawson and McCullough (2004) concluded that due to circadian biology, fatigue accumulation and recovery develops in a significant non-linear way. For example, prescriptive limitations on shift duration generally assume that a break of a given length has a uniform recovery value with respect to mental fatigue. While this may be relatively true with respect to physical fatigue, it is demonstrably not the case with respect to mental fatigue. Indeed, providing the same length of time off during the subjective day, as opposed to subjective night, will result in a significantly reduced amount of recovery sleep. In his studies Dawson therefore concludes the following: Estimating the level of mental fatigue associated with a given pattern of work is linked more to the timing and duration of sleep and wake within the break, rather than the duration of the break alone. Although there is clear scientific evidence to support this notion, few regulatory models acknowledge it explicitly.
- HOS is easy to implement and control, as it is ‘hard’ data (Dawson and McCullough, 2004)
- HOS can be easily combined with a broad spectrum of measures to improve alertness and fatigue level
- Regulatory models based only on shift duration are unlikely to produce congruence between what is safe and what is permitted and what is unsafe and not permitted (Dawson and McCullough, 2004, Baumgartner (ATM/HLG5), 2012)
- It is a static form of safety management. The demands of operating diverse and complex safety-critical air traffic services require flexibility that cannot be obtained by a rigid prescriptive approach. The prescriptive limits might impose unrealistic expectations on operations or regulations (Canada tripartite steering committee on ATC fatigue, 2001, London Department for Transport, 2010, Brathwaite, 2012)
- Hours of Service limitations are a ‘one size fits all’ approach to managing a complex problem. In isolation, a set of simple limits on work and rest hours cannot take into account the impact on fatigue of operational factors such as differences in workload, working conditions and personal factors, such as age, health, and domestic and social activities (Canada tripartite steering committee on ATC fatigue, 2001, London Department for Transport, 2010)
- Another determinant of fatigue that is largely ignored by ‘hours of work’ limitations is the influence of the body clock (London Department for Transport, 2010)
- The application of prescriptive duty limitations may be an appropriate control for physical fatigue, this cannot be assumed for mental fatigue (Dawson and McCullough, 2004). In the case of mental fatigue, this approach incorrectly assumes that the determinants of mental fatigue are similar to those for physical fatigue. While it is true that mental fatigue does, in part, accumulate in a relatively linear manner, there are significant additional non-linearity driving the dynamics of fatigue and recovery processes for mental fatigue. In short; dynamics that work on the recovery of physical fatigue, do not apply for mental fatigue, due to circadian biology.
2.6.3 Tool 3: Roster Model / Scheduling
Following and expanding upon the HOS model, roster models were developed. In these rosters a schedule is planned on a stable or a flexible base, aimed at optimal use of the resources, whilst limiting the risks of fatigue.
Organisation of duty cycles is a difficult issue as there is no ideal scheduling. Scheduling is always a compromise between safety, health requirements, productivity and social acceptance. One of the first aspects to consider is the direction of shift, i.e. clockwise (delayed rotation) or counter clockwise (advanced rotation) (Cabon, 2011). When a roster is set up, it is advised to keep the following in consideration: forward (clockwise) rotation shifts are more tolerable by the body (A pattern of work in which the starting time of successive rostered shifts, or blocks of rostered shifts, changes in a clockwise direction). Compared to forward rotation, backward rotation causes increased fatigue and sleep problems. (Eurocontrol, Managing shiftwork in European ATM, 2006).
As workload has a significant effect on fatiguing, rostering should be constantly adjusted and reviewed to match the demands in traffic and to avoid overload or underload of ATCOs. When setting start- and end times and lengths of shifts, the circadian rhythm should be taken into account (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006). To supplement this, if possible roster makers should take account of individual employee preferences in his/her roster, in order that these may be accommodated as far as practicable and reasonable. A common sense approach to good shift work management is required (Canada tripartite steering committee on ATC fatigue, 2001)
Other issues to take into account are maximum number of sequential working days, hours depending on time of day, and minimum days of recovery. Using this approach, a roster or schedule is deemed acceptable if it does not contain any unapproved features (such as the maximum length of a duty, and the allowance of breaks). The advantage of this approach is that it treats the roster as an integrated whole (Dawson and McCullough, 2004).
Rest periods between shifts need to be sufficiently long to provide recovery. The normal required number of uninterrupted sleep for an individual is seven or eight hours. As a consequence a minimum of 10 hours between shifts is the accepted norm to allow for adequate sleep (Canada tripartite steering committee on ATC fatigue, 2001). Avoid shift exchange or overtime that reduces the rest period to less than two consecutive calendar days off after five or more consecutive days worked, thereby mitigating accumulated fatigue/sleep loss (Canada tripartite steering committee on ATC fatigue, 2001, Di Milia et al, 2009, London Department for Transport, 2010, Gimbrere, 2011). When this limit is exceeded additional measures must be taken into account in the roster to reduce the increased risk of fatigue.
It is recommended that the number of consecutive night shifts should be limited as far as possible with a recommended number of two but an absolute maximum of three. After a night shift, the rest period to properly recover should be at least 24 hours, but preferably longer. Where possible, avoid midnight shifts that exceed 8 hours, and target the shift to start late (>10:30) and finish early (<7:30) When this is not possible, implement appropriate fatigue countermeasures; e.g. 24-hour period off-time at the end of the last midnight shift. Staffing levels during night shift must be carefully considered by management in coordination with the ATCOs (Brathwaite, 2012). For those controllers who have very heavy traffic workloads during night shifts additional relief should be considered as an appropriate countermeasure to sleepiness and fatigue in order to increase the safety margins and to reduce subsequent daytime sleepiness (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006).
- It can be stable or flexible (as desired)
- It can be constantly reviewed and adjusted to match with traffic demands, constraints and expectations (Marien, 2011)
- Individual preferences can be taken into account
- Difficult to generalise to novel or innovative rosters or schedules (Canada tripartite steering committee on ATC fatigue, 2001, Dawson and McCullough, 2004)
- Fails to identify individual differences in fatigue-related risks (incl. demographic factors) (Canada tripartite steering committee on ATC fatigue, 2001, Dawson and McCullough, 2004) and this could be difficult to implement
- Fails to distinguish between work-related causes of fatigue and fatigue due to non- work related causes (Canada tripartite steering committee on ATC fatigue, 2001, Dawson and McCullough, 2004); It only provides a solution to a limited part of the factors that cause fatigue
- It might impose unrealistic expectations on operations or regulations (London Department for Transport, 2010, Brathwaite, 2012)
2.6.4 Tool 4 Prior sleep wake model (PSWM)
(Prior sleep wake model (Dawson and McCullough, 2004)
From research of road safety the Prior sleep wake Model (PSWM) has been designed by Dawson et al. The conceptual basis of this model is that fatigue is better estimated from prior sleep / wake behaviour than from schedules or hours of service at work. Using this model, an organisation can define task specific thresholds for sleep and wakefulness based on the amount of sleep obtained in the 24 and 48 hours prior to commencing work. Where aggregated or individual sleep / wake values fail to reach pre–designed thresholds, the increased likelihood of fatigue would require a greater level of hazard control to prevent an actual accident from occurring (Dawson and McCullough, 2004)
- Provides insight in the relationship between sleep obtained (rather than time worked) and the level of fatigue a person is experiencing
- It is a meaningful addition to the understanding of fatigue mitigation. A FRMS based on PSWM, combined with other measures to cover the remaining risks in the risk matrix, could provide a useful tool
- Studies show that the PSWM in current state cannot be implemented in a FRMS as the research still has to outgrow the conceptual phase
- In a working environment measuring the PSWM on an objective manner is difficult and cannot be controlled
- The effects of sleeping on biologically abnormal hours (outside your circadian rhythm) have not sufficiently been established in relation to the outcome of the PSWM. The same can be said of the irregularity of the sleep obtained
- The model does not cover all of the factors that influence the fatigue level of a person. Personal factors are taken into account, though it fails to emphasise the personal responsibility.
- Implementation of PSWM could be difficult as it could result in a bureaucratic procedure, without any means of controlling the correctness of the data used.
2.6.5 Tool 5 Awareness of fatigue and Team Resource Management (TRM)
A major part of fatigue related factors concern factors that relate to personal lifestyle. Awareness of the risks of fatigue and how one can recognise and reduce these risks is imperative for a well working FRMS. To create this understanding training should be provided to ATCOs (Canada tripartite steering committee on ATC fatigue, 2001). Fatigue management is a shared responsibility between all parties involved (e.g. employer, individual employees). All parties have a vital role, which must be accepted by all ‘players’.
The ANSP should encourage personnel to take action when symptoms of fatigue are identified. As TRM has showed, the promotion of a culture of a jointly felt responsibility is essential, as is an open culture where employees feel safe to speak their minds freely. TRM could be a useful tool to recognize the onset of fatigue in yourself or in others and increase the willingness to take action.
The ANSP is responsible for providing optimal working conditions, information on fatigue and facilities to enable fatigue to be effectively managed; training on fatigue management and enable workplaces to adopt practices that minimise fatigue (Canada tripartite steering committee on ATC fatigue, 2001).
ATCOs are obligated to make appropriate use of rest time and report fit for duty. Employees must therefore take responsibility to make the appropriate lifestyle decisions consistent with the nature and demands of shift work (Transportation Safety Board of Canada, 2011).
Fatigue risk management training is a foundation for many of the defences against fatigue. It provides employees with knowledge on how to identify, avoid, mitigate and report fatigue issues. Education of employees on their responsibility in reducing fatigue (Canada tripartite steering committee on ATC fatigue, 2001, Mein, 2001, Transportation Safety Board of Canada, 2011, Gimbrere, 2011) is therefore imperative. Fatigue awareness training should reflect current scientific findings and fatigue mitigation strategies. Support should be personalised and include practical operational needs (Gimbrere, 2011). Supervisors should be trained to identify and consider the fatigue status of individuals prior to commencing shifts or extending shift lengths (Canada tripartite steering committee on ATC fatigue, 2001). To create awareness there are special programmes developed to measure fatigue (London Department for Transport, 2010). These Fatigue models use ‘science-based’ algorithms to predict the fatigue associated with work hours, based on variables such as the duration and timing of shifts and breaks (e.g. FAID (2003), the Health and Safety Executive (HSE) Fatigue/Risk Index (2006), SAFE (2007), FIYT (2009) and CAS-5 (2011).
The development of a monitoring system such as a symptom checklist for recognition of fatigue signs is recommended. The checklist can score behaviour and visible signs of fatigue, combined with supervisor knowledge of the individual ATCO.
Nowadays software has been developed that can administrate the activities of employees in order to determine a fatigue index score. The application of such software is not deemed practicably applicable at this time it forms a great intrusion of the employee’s personal private life. It is suggested that employee’s awareness is increased by training and emphasis on personal responsibilities (ICAO FRMS Manual for Regulators, Doc 9966, 2011).
- Education leads to well-informed employees, whereas an open culture will lead to a joint responsibility to prevent risks resulting from reduced alertness (due to fatigue).
- This tool will only be effective when an open culture has been established. Training alone will not change a culture.
2.6.6 Tool 6 Outcome Based fatigue risk management
Through analysis of Fatigue Related Incidents and Errors (FRI/FRE), many things can be learned relating to the operational process. For each incident a trajectory of errors can be established. For this the fatigue risk trajectory model was designed (Dawson and McCullough, 2004):
As shown in the fatigue risk error model an incident is always preceded by a sequence of events. Thus a fatigue related incident is always preceded by fatigue related error(s), which in turn can be associated with an individual in a fatigued state. This model provides an adequate tool for analysis of fatigue related incidents as it provides data for mitigation of fatigue risks in future situations. In order to do so the following recommendations can be found in the studied literature: (Gimbrere, 2011)
- Gather data to support fatigue analysis and mitigations and (Canada tripartite steering committee on ATC fatigue, 2001).
- Emphasise the need for the collection of fatigue related data during the conduct of incident investigations.
- Develop methods and performance based metrics to measure and evaluate the effectiveness of fatigue management strategies as they are implemented.
When implemented correctly analysis should be performed following any found incident related error, and counter measures should be taken. This way it is possible to continuously improve the FRMS. For this reason the ANSP should ensure that remedial actions, necessary to effectively mitigate the risks associated with fatigue hazards, are implemented promptly.
In order to allow the ANSP to continuously improve their FRMS, data of applied measures and the results of incidents/accidents related to fatigue must, in a auditable way, be gathered (and reported upon) and subsequently be analysed.
- The tool provides a means for continuous assessment and improvement on the established FRMS
- The tool provides an increased awareness of employees concerning fatigue risks
- The tool is a reactive tool, as it can only be applied when an incident has occurred and it was recognised as such
- The tool is a part of the risk mitigation, but should not be the only tool in the FRMS applied
- Significant risks associated with poor enforcement and assessment
2.6.7 Other preconditions to avoid fatigue
The prerequisite of any well working FRMS is the existence of sufficient and adequately trained staff. All tools and measures depend on given boundaries for what is deemed acceptable in sense of fatigue accumulation. Failing to allocate a sufficient level of staff will severely weaken any measure taken.
Work environment; Ergonomics
Factors to consider are human-machine-interface, situational awareness, visual displays and alerting, auditory alerting and data entry. Employ ergonomics early in the design or redesign of the workplace. Employ ergonomic design criteria when designing or redesigning napping, break and exercise facilities (Canada tripartite steering committee on ATC fatigue, 2001).
Social life, personal fitness and diet
Next to these tools it is imperative to recognise the more personal situations that can affect the ATCOs fatigue namely; social life, personal fitness and diet. It would be well advised to promote a healthy lifestyle.
2.7 Conclusion on theoretical fatigue management systems
The basis for applying tools to mitigate the risks of fatigue is adequate staffing and overtime policy. There also is a responsibility for the ATCO to obtain sufficient sleep (quantity and quality) before a shift begins. Furthermore the work environment for ATCO’s should support an optimal performance with a minimum of fatigue inducing elements.
The following is a summary of the possible tools described above:
Tool 1: Breaks
In our opinion even though breaks in accordance to the studies show to have effect, the drafting of a FRMS based on breaks alone is not sufficient. It is however a viable addition to a framework of measures to be taken in the mitigation of fatigue.
With regard to breaks the following recommendations are found in the literature that should be regarded as guidelines in the process:
1.1. The established norm is two hours on position followed by a relief break. This applies when handling complex and busy air traffic. This period may be extended to four hours (should not be exceeded) in the case of a low workload and subject to other employed mitigating measures (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006, London Department for Transport, 2010, Transportation Safety Board of Canada, 2011, Baumgartner (ATM/HLG5), 2012).
1.2. Psycho-physiological studies have shown that after 2 hours of duty at busy ATC workplaces a break or relocation to a less stressful position should be offered. Moreover, ATCOs should be informed, sensitised, and trained with respect to the typical human ‘overshooting relax’ response after stress peaks.
1.3. The minimum duration of a break should be 10 minutes plus 10 minutes per hour of work (Eurocontrol, Managing shiftwork in European ATM, 2006).
1.4. Breaks should allow napping (typically 20 to 40 minutes) with ample time (20 minutes) to overcome subsequent inertia (period of grogginess experienced upon waking).
1.5. The ability to sleep/nap during midnight shifts has been found to reduce the level of performance degradation experienced by controllers working these shifts. When only limited time is available study shows that the best reaction times were demonstrated after naps of 20 minutes maximum. Also a period of 20 minutes should be allowed after waking to return to full effectiveness (to overcome the effects of sleep inertia) (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006, UK CAA, 2007, Transportation Safety Board of Canada, 2011, Gimbrere, 2011, Anthony, 2011, Cabon, 2011, Brathwaite, 2012). When more time is available a recuperative break of up to 2.5 hours is advised during the midnight shift (Gimbrere, 2011).
1.6. Physical arrangements (suitable napping facilities (pre/post shift naps and midnights)), that allow for quiet, restful breaks must be in place. Break facilities need to be suitably located and furnished to promote fatigue recover, suitable physical fitness facilities, accessible outdoor rest and relax facilities and sufficient break periods must be provided to allow for strategic naps during night shift (Canada tripartite steering committee on ATC fatigue, 2001).
1.7. Duty rosters management must provide: relief controllers, adapted rest periods and sufficient break periods for controllers to try to maintain their daily eating habits regardless of which shift they are working (Brathwaite, 2012).
Tool 2: Hours of service (HOS) model
For the purpose of managing fatigue in ANSPs this method in our opinion is inadequate in isolation. Hours of service does not recognize the complex and demanding mechanism ANSPs face regarding fatigue. However studies on the shift length have shown an increased risk when a shift exceeds a maximum of 8 hours on average. In this case there is an exponential increase in probability of errors and critically impairment to the level of alertness. We would suggest that these findings are taking into account in the design of any FRMS.
With regard to the HOS the following recommendations are found in the literature that should be adhered to in a FRMS:
2.1. Incidentally the length of a shift may exceed the 8 hours with a maximum of 10 hours per day. However over a longer period of time the average of 8 hours per working day should not be exceeded as there is an increased risk when shifts exceed the 8 hours (Eurocontrol, Managing shiftwork in European ATM, 2006).
2.2. Adopt shift scheduling strategies that reduce the probability of the ATCOs experiencing sleep loss when working hours of overtime. Identify and implement methods that will lead to fewer and shorter overtime shifts (Canada tripartite steering committee on ATC fatigue, 2001, Brathwaite, 2012).
2.3. Combining overtime with regular duties shortly before or just after night shifts must be avoided (Canada tripartite steering committee on ATC fatigue, 2001, Brathwaite, 2012).
Tool 3: Roster/scheduling
Rostering provides a viable solution for some of the factors that cause fatigue. However it should not be implemented as sole measure of mitigation into an FRMS. As part of a mix of measures, it currently is the best method of work planning.
With regard to the roster the following recommendations are found in the literature that should be regarded as guidelines in a FRMS:
3.1. Rostering should be constantly adjusted and reviewed to match the demands in traffic requirement and to avoid overload or underload of ATCO’s (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006).
3.2. The circadian rhythm should be taken into account when setting start-and end times and lengths of shifts (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006).
3.3. If possible roster makers should take account of individual employee preferences (chronotype, commuting time) in his/her roster, in order that these may be accommodated as far as practicable and reasonable (Canada tripartite steering committee on ATC fatigue, 2001).
3.4. A minimum of 10 hours between shifts is the accepted norm to allow for adequate sleep (Canada tripartite steering committee on ATC fatigue, 2001, Di Milia et al, 2009, London Department for Transport, 2010, Gimbrere, 2011).
3.5. Avoid shift exchange or overtime that reduces the rest period to less than two consecutive calendar days off after five or more consecutive days worked, thereby mitigating accumulated fatigue/sleep loss (Canada tripartite steering committee on ATC fatigue, 2001).
3.6. It is recommended that the number of consecutive night shifts should be limited as far as possible with a recommended number of two but an absolute maximum of three. After a night shift, the rest period to properly recover should be as long as possible, but at least it should not be less than 24 hours (Canada tripartite steering committee on ATC fatigue, 2001, Eurocontrol, Managing shiftwork in European ATM, 2006).
3.7. Staffing levels during night shift must be carefully considered by management in coordination with the ATCOs. For those controllers who have very heavy traffic workloads during night shifts additional relief should be considered as an appropriate countermeasure to sleepiness and fatigue in order to increase the safety margins and to reduce subsequent daytime sleepiness (Brathwaite, 2012).
3.8. Nowadays scheduling design can be supported and improved by the use of specific software. It seems advisable to research the effective introduction and application of such software (London Department for Transport, 2010).
Tool 4: Prior sleep wake model (PSWM)
Scientifically the PSWN provides a strong relationship between fatigue and sleep obtained. The effect of obtained sleep on fatigue and alertness provides an important understanding of biological mechanisms.
Current research was performed primarily in lab surroundings, with no regards to the effects of the circadian cycle on the quality of the sleep obtained (test subjects slept on ‘normal’ sleeping hours). Implementing the findings in a working environment at this point and time therefore would be premature.
The findings do however provide important insights on the functionality of human biology and, if shared judiciously, can increase the understanding of ANSPs, roster making employees and ATCO’s on the conditions that should be met in order to perform ATC with an adequate level of alertness.
When science has advanced and tests in working environment have been performed, the feasibility of inclusion of a PSWN model in a FRMS should be explored. For now only the understanding of the PSWM can be implemented in fatigue related staff training.
Tool 5: Awareness of fatigue and Team Resource Management (TRM)
Awareness of fatigue risks and fatigue related risks is one of the vital pillars of any well working FRMS. It is not an all-inclusive solution for the problem however other means of mitigation will have little to no effect when the culture within the working environment does not recognise the importance of a FRMS, or when the staff responsible for enforcing FRMS are not adequately trained.
The culture needs to be open and ATCOs need to be responsible to adjust personal lifestyle with the high demands of the position.
With regard to awareness of fatigue and TRM the following recommendations should be taken into account:
5.1. Fatigue management is a shared responsibility between all parties involved. This
must be accepted by all ‘players’. In order to facilitate this, the culture should be open and employees should be free to speak their minds (Canada tripartite steering committee on ATC fatigue, 2001).
5.2. Awareness campaigns should teach ATCOs how to recognize signs of fatigue at an early stage and what countermeasures could be implemented to counteract the problem (London Department for Transport, 2010).
5.3. The ANSP should also encourage personnel to take action when symptoms of fatigue are identified. For this a culture in which fatigue management is seen as a shared responsibility is essential (TRM). Supervisors should be trained to identify and consider the fatigue status of individuals prior to extending shift lengths (Canada tripartite steering committee on ATC fatigue, 2001).
5.4. The ANSP is responsible for providing working conditions, information and facilities to enable fatigue to be effectively managed; training on fatigue management and enable workplaces to adopt practices that minimise fatigue (Canada tripartite steering committee on ATC fatigue, 2001).
5.5. ATCOs are obligated to make appropriate use of rest time and report fit for duty. Employees must therefore take responsibility to make the appropriate lifestyle decisions consistent with the nature and demands of shift work (Transportation Safety Board of Canada, 2011).
5.6. The management should support the on-going adoption of a positive safety culture.
Tool 6: Outcome Based fatigue risk management (FRI/FRE and fatigue risk trajectory model)
The implementation of the post error analysis of the fatigue risk trajectory, for example by the use of the FRI/FRE model, provides the means of a continuously learning organisation for fatigue risk mitigation. It should therefore be implemented in any FRMS.
With regard to outcome based fatigue risk management the following recommendations can be made:
6.1. Gather data to support fatigue analysis and mitigations (fatigue reports, confidential reports, audit reports, data regarding incidents and accidents). Developing better understanding of fatigue to determine where best to direct resources for addressing fatigue (London Department for Transport, 2010, Gimbrere, 2011)
6.2. Emphasise the need for the collection of fatigue related data during the conduct of incident investigations. Develop methods and performance based metrics to measure and evaluate the effectiveness of fatigue management strategies as they are implemented (Canada tripartite steering committee on ATC fatigue, 2001).
6.3. The ANSP should ensure that remedial actions, necessary to effectively mitigate the risks associated with fatigue hazards, are implemented promptly.
Based on the outcome of the literature a FRMS elements model can be defined. In the model below we follow the fatigue risk trajectory of Dawson and McCullough, (2004), expanded with additional findings from the literature. In this FRMS elements model we have recognised so- called prerequisites and tools. Pre-requisites being elements of a FRMS that are non-active but detrimental to the effective management of fatigue. The tools provide insight in the active measures to be taken in day-to-day operations.
FRMS elements model:
The FRMS elements model above will be used to compare the FRMSs under review, in paragraph 3, to draw conclusions on the quality of the FRMS, based on most current knowledge of the management of fatigue.
The FRMS elements model can be adjusted when new scientific research indicates different approaches. The mentioned control mechanisms should be included in the more overall safety management system (SMS) alongside the other safety related issues and following the same principles (Dawson and McCullough, 2004).
Comparison to current policies
The aim of an effective FRMS is to reduce the potential negative impact of fatigue on safety. In the past rest (sleep) was identified as the principle means to mitigate fatigue. However in 24/7 operations involving human operators and shift work, fatigue will always be a potential safety risk. Therefore, in addition to measures that aim to reduce fatigue related risks, specific fatigue mitigation strategy needs to be employed to minimise the extent and cause of degraded human performance during operational duties. Finally there must be mitigation strategies in place to form a final line of defence so that human errors posing a potential threat to safety result from fatigue-degraded human performance, the errors would be captured or otherwise diverted from resulting in an incident, accident or other occurrence (Canada tripartite steering committee on ATC fatigue, 2001).
Awareness of fatigue related risks resulting from fatigue is ever growing at this point in time; ANSPs and aviation organizations alike acknowledge the need to mitigate risk that threaten air traffic safety. In this chapter we will compare the fatigue risk mitigation guidelines of ICAO and IFATCA respectively, for applicability in the operations of ANSPs.
The ICAO Standards and Recommended Practices (SARPs) regarding FRMS Requirements (Annex 6, Part I, chapter 4, 4.10.6 and Appendix 8) are reviewed in 3.2, the IFATCA recommendations regarding FRMS and fatigue are reviewed in 3.3. In 3.4 the tools employed in the respective recommended fatigue risk manuals, are compared to the found preferred composition of a fatigue risk management system as shown in paragraph 2. In 3.5 a conclusion will be drawn upon the usefulness of the respective guidelines for ANSPs to aid them in their implementation of the recommended FRMS.
3.2 ICAO SARPS
ICAO has issued SARPs for flight and cabin crew on the issue of fatigue management in Annex 6, Part I, chapter 4, 4.10.6 (ICAO FRMS Manual for Regulators, Doc 9966, 2011, ICAO FRMS Implementation Guide for Operators, 2011), including particular standards that enable the effective regulation of FRMS. These are, in turn, supported by Annex 6 Appendix 8, which details the requirements for a FRMS. For the purpose of this paper the detailed requirements of an FRMS are evaluated for the appropriateness for ANSPs to apply these guidelines in their implementation of a FRMS in the ANSP’s safety management systems (SMS).
The SARPs as defined by ICAO include the risk assessment phase. Although in order to set up and implement a FRMS it is necessary to understand the risks, for this paper we did not include a risk assessment phase in the recommendations. As risks are mostly generic, in this paper we focus on the advised elements of a FRMS instead. When deemed necessary, the process of setting up individual risk assessment procedures can be included in another paper.
The SARPs emphasise that regulations should be established for the purpose of managing fatigue. These regulations shall be based upon scientific principles and knowledge, with the aim of ensuring that flight and cabin crew members are performing at an adequate level of alertness.
The SARPs however state that it is the responsibility of the state to establish fatigue managing regulations, rather than promoting the own responsibility of the organization to self-regulate the risks related to fatigue. This would imply that rather than the organisation (in the SARP the operator), the state is responsible for the safety of its operations. IFATCA does not oppose state involvement in the safety of air traffic by the issuance of a set of minimum requirements of a FRMS, however emphasise that internally developed systems can fit better in the organisation’s needs, will need less external supervision on the correct implementation thereof and is likely to be more effective than an external set of guidelines and rules. For the purpose of this paper we focus on the recommended combination of measures to be taken by the ANSP, rather than the recommended regulations to be set by governments.
The prerequisite staffing and overtime policy as defined in the FRMS elements model is not considered a factor in the SARPs, and therefore deviates from the advised FRMS elements model.
The SARPs take into account the necessary opportunity to sleep for flight and cabin crew members and to comment on the quality of sleep obtained (ICAO FRMS Manual for Regulators, Doc 9966, 2011, ICAO FRMS Implementation Guide for Operators, 2011). The recommendations made however focus on the issues as befall pilots and flight crew, and therefore do not address the issues ATCOs might have.
ICAO Document 9966 looks at the implementation of a FRMS for flight and cabin crew. Short breaks are not a typical instrument to be applied on flight and cabin crew, while they can be a viable method to reduce fatigue for ATCO’s.
The SARPs leave out the maximum shift length recommendation. As the SARPs are solely aimed at flight and cabin crew this is understandable, as a shift is dictated by the length of the flight. Instead recommendations are made on the regulation of flight time duty periods and rest period limitations. These recommendations aim at the same problem of maximum working time, and is thus far comparable to the in paragraph 2.6.2 (HOS model) recommended shift and over hours limitation. This automatically has repercussions on the recommended applied rostering / scheduling. This being said the SARPs are comprehensible, but they do not provide guidance to ANSP’s on how to implement a roster that reduces fatigue risks.
The SARPs introduce the joint responsibility of both operator and personnel, in the same manner as is advised upon in the previous paragraph. The SARPs refer to recommended training of personnel and the necessary commitment of all staff, from management to flight and cabin crew, to reduce fatigue related risks. The SARPs even suggest a required accountability of personnel when these rules are not followed. Although accountability can be a way of enforcing regulation to be followed, the enforcing thereof in this subject could be very difficult. For this reason the accountability was not incorporated in the FRMS elements model. The requirement to make attendance mandatory to fatigue related training programs however is a valuable one, which can be incorporated in the FRMS-model for ANSPs.
Finally, the outcome based FRM is incorporated in the SARPs, by ensuring that output, results and deviations from regulations are reported upon and used for further refinement of the regulations, by the operator.
3.3 IFATCA Technical & Professional Manual 2012
In the Technical and Professional Manual 2012, IFATCA has made recommendations regarding fatigue risks. IFATCA has narrowed down the hours for which the regulations should be applied as the hours of ‘operational duty’. This de facto means that in the IFATCA policy the management of the hours out of active duty are not governed by any rule or recommendation.
There is no direct reference to the personal responsibility of the ATCO with regard to fatigue in the IFATCA Manual. As is shown in this paper IFATCA considers that one of the vital pillars of the management of fatigue related risks is the joint responsibility of both ANSP – to manage work time within the latest established boundaries in terms of length of duty, time between shifts and so on – and the ATCO – to plan work and private time in such a manner that the work duties cannot be impaired by disregard of necessary personal rest periods (i.e. partying all night right before an early morning shift leads to an increased fatigue related risk).
Policy WC 1.3.2. stipulates specifically the maximum length of a shift, the maximum hours of active duty per week and the minimum rest hours. With a difference of 30 minutes the hours taken into account are defined a little more restrictively then the recommended hours as found in the research used in this paper. It can therefore be considered to be conservative, but also safe when they are implemented in an active duty roster.
Maximum operational time and minimum break time is specified in regard to the FMRS element of breaks. In Policy MED 2.2.5 the requirement of management to allow for strategic naps and to provide room for this purpose is included.
A mention in WC 1.3.2 is made with regards to the liability of the controller, which would be void, as per recommendation, when the controller has registered formal complaint towards the duty roster which is applied.
Policy WC 1.3.5 addresses the issue of staffing levels, and considers established documentation on the adverse effects of extended hours of work. In the FRMS elements model presented in this paper this is considered one of the prerequisites for an adequate FRMS. It is not specified whether overtime in this policy should be viewed ‘on top of’ the recommended shift duration, or as part thereof. For this purpose IFATCA suggests overtime to be voluntary, without any pressure from management or peers. In policy MED 2.2.5 the recommendation is made to avoid overtime at all cost shortly before or just after a night shift.
Policy MED 2.2.5 suggests member associations identify fatigue related risks. In the FRMS elements model, it states that management has the prime role in the avoidance of fatigue related risks. In this paper however it is concluded that even though management does have a major role, the personal role of the ATCO is integral to a FRMS model, as not all risks can be managed by rules and regulations of the ANSP.
In policy MED 2.2.5 the physical arrangements such as rest / break areas, but also the arrangements allowing the ATCOs to continue their daily eating habits and rooms for the strategic naps (20 – 50 minutes according to the policy), are expected to be provided for by management. How these arrangements should be set up is not specified in the policy. These breaks are considered to be included in the duty time.
In policy MED 2.2.5. extra emphasis is made on the staffing levels, especially at night time and / combined with workload.
Policy MED2.2.5 comments on the awareness for MAs and their management of fatigue risks and causes. MAs should inform members about the causes of fatigue in ATC so that they can identify those to which they are most exposed to. Members should be informed about the countermeasures available. Education in human factors is mentioned, including theory about the physiological principles related to sleep and circadian rhythms, both in controllers retraining and basic education. Such training should include knowledge of ways to take deliberate actions (countermeasures) to better meet controllers’ operational requirements.
Furthermore MAs should advise their members to seek professional psychological advice when they believe that they are subject to excessive stress-inducing agents, any indications or symptoms are not mentioned.
Policy MED 2.2.5 concludes with:
|The Regulator / Legislator should:
In the FRMS elements model the auditable FMS relates to the outcome based fatigue management system that should be part of the SMS.
3.4 overall comparison
In this paragraph we compare the recommended elements of a FRMS to the respective regulations of the reviewed organizations, in a table. When the control mechanism as mentioned in the respective regulation can be applied by ANSPs, the table shows ‘YES’ when it isn’t it shows ‘NO’. Other remarks are referred to by number.
1: The general recommendation can be used. It however needs to be recommendation aimed at operators and flight and cabin crew into a recommendation applicable for air traffic controllers.
2: The application of the forward rotating roster is neither included in the ICAO nor in the IFATCA recommendations. They should be included, in accordance with the findings in the literature.
3: Current IFATCA policy focusses on the responsibility of the ANSP solely, disregarding the ATCOs responsibility. Including the latter would improve the IFATCA policy.
4: Only the auditability of the applied FRMS is taken into account in the IFATCA policy. The outcome based improvement of the FRMS should also be included in the policy.
3.6 Conclusion on current ICAO and IFATCA policy
ICAO Doc 9966 is written specifically to fit the issues and problems as they are assessed for flight crew and airline operators. Their document and recommended FRMS cannot be used by ANSPs in order to implement a FRMS. However the elements of the ICAO SARP do cover (most of the) recommended elements of an FRMS. Therefore it is likely that parts of the ICAO document after judicious revision of the recommended Standards (SARPS) can provide a solid guideline on which ANSPs can base the implementation of the fatigue risk management as part of their SMS.
At this moment IFATCA has no policy on FRMS but only multiple policies on fatigue related issues. A parallel can be found between the recommendations of IFATCA and the established elements of a FRMS in accordance with the FRMS elements model presented in this paper. It is the recommendation that the model of FRMS elements (paragraph 2.8), is included in the IFATCA policy on FRMS. The current IFATCA policy has to be revised and completed to cover all items mentioned in the FRMS elements model.
In this paper PLC has reviewed the available scientific findings relating fatigue and the management thereof in comparison with ICAO and IFATCA policy to find recommendations and guidance on the adoption of FRMS additions in accordance.
This paper provides insight into the wide range of factors that influence the state of fatigue of an ATCO, from work related, environmental to personal factors.
4.2 Recommended measures of mitigation of fatigue related risks
In the scientific literature a broad array of measures can be found, where each of these measures specifically target an element of fatigue inducing factors. In this paper PLC has reviewed these theoretical measures in order to establish the applicability and the viability.
The findings are that many of the newer measures provide an overlap with the older ones and that the previously accepted measure of mitigation of fatigue (p.a. working hours and rostering) have been found to be lacking.
Based on the relative state of the theoretical development, and to what degree it has proven itself in the field, the measures have been evaluated for usability in the day-to-day operations of ANSPs.
Following this comprehensive analysis PLC created a model of a theoretical ideal FRMS. The model has been set up to show the general direction of the FRMS elements. The specifics of the elements as established in the model in this paper are not in the scope of this paper, these should be further defined in future studies.
In this FRMS elements model we have recognized prerequisites and tools. Prerequisites being elements of a FRMS that are non-active, but detrimental to the effective management of fatigue. The tools provide inside in the active measures to be taken in the day-to-day operation.
4.3 Current applied measures in ICAO and IFATCA policies
Relevant articles of ICAO and IFATCA policies concerning fatigue and FRMS have been compared to the elements in the established FRMS elements model.
In the analysis PLC found that neither current ICAO measures nor IFATCA guidelines can be used by ANSPs as an all-encompassing policy to cover fatigue related risks in the operations. In order to draft a complete policy, elements from both need to be combined.
5.1. To insert in the manual at MED 2.2.5 Fatigue in Air Traffic Control:
ATCO fatigue is defined as follows:
A physiological state of reduced mental or physical performance capability resulting from sleep loss or extended wakefulness, circadian phase, or workload (mental and/or physical activity), affecting the subjective state, that can impair an air traffic controller’s alertness and ability to perform safety related duties.
5.2. It is recommended that the FRMS elements model be included in the IFATCA Technical and Professional manual as provisional policy at MED 2.2.5 Fatigue in Air Traffic Control:
The FRMS elements model
5.3. It is recommended that specifics of the FRMS elements model should be further studied by IFATCA and presented as a working paper at conference 2014. As part of this study, existing IFATCA policy on fatigue should be reviewed.
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Last Update: September 30, 2020