Effects of fatigue on human performance – Why the TSB investigates for fatigue in every occurrence
12 March 2015
Posted by: Missy Rudin-Brown
Despite the fact that most people need around 8 hours of sleep every night to feel well-rested, 30% of Canadians report getting fewer than 6 hours of sleep per night, and 60% report feeling tired “most of the time”.Footnote 1 Historically, getting by on as little sleep as possible – especially in some industries such as commercial fishing, rail operations and aviation – was seen as a necessary part of operations rather than as something that needed to be discouraged. Insufficient or poor quality sleep due to long working hours, sleeping at a time of day when one is usually awake, or being awake at a time of day when one usually sleeps, are all factors that contribute to fatigue and the resulting feeling of tiredness. “Fatigue” is the feeling of tiredness that one experiences when not getting enough, or enough good quality, sleep. People working in today’s 24/7, ‘non-stop service’ transportation industry, are particularly at risk of experiencing fatigue.
How fatigue affects performance
Fatigue can affect a person’s performance in a variety of ways. People who are fatigued are more easily distracted, are less able to concentrate, tend to forget things more easily, take longer to solve problems, make more mistakes, have slower reaction times, and take more risks than they might otherwise. At the extreme, they might fall asleep while operating a vehicle! But the risks of fatigue in terms of transportation safety are not limited to vehicle operators. The performance of individuals in other roles, for example managers who schedule work and oversee operations, traffic control officers, mechanics, technicians, baggage handlers, and those providing customer service, can also negatively impact safety if it is impaired by fatigue. Being tired can also make a person feel angry or irritable, which can affect the performance of those around them.
Investigating for fatigue
Because fatigue is so common and accepted in our society today, it is necessary for investigations to consider it in every occurrence. As investigators, we need to rigorously collect sleep data as soon as possible during an investigation.
Did fatigue exist?
A first step is to request sleep-wake and work histories for all operational personnel involved in an occurrence. To help with this process, the TSB has developed an innovative tool for investigating fatigue that can be used to collect and analyse data. This tool is used to convincingly document the existence of fatigue in transportation accidents, as well as its influence on safety, so that those responsible for transportation safety management will be in a better position to implement effective solutions, such as fatigue risk management programs (FRMS). People’s memory of their sleep patterns fade quickly. That’s why interviews need to be conducted as soon as possible after an accident. Investigators will ask about a person’s normal sleep habits – how long and at what time they usually sleep when they have every opportunity to get rest. They will also assess a person’s physical characteristics, ask about medical conditions, the use of alcohol or drugs (including prescribed and over-the-counter medication), and the sleep environment. Obstructive sleep apnea, sleep walking, night terrors, and restless legs syndrome are other sleep-related conditions that can limit the quality and quantity of sleep a person obtains.
Did fatigue contribute to the occurrence?
Once it is determined that fatigue was present at the time of an accident, we need to determine whether it influenced safety and contributed to the occurrence. Just because someone was in a fatigued state during the lead-up to an accident does not necessarily mean that fatigue’s effect on performance contributed to the accident. Understanding whether the causal or contributing performance impairments could have been due to fatigue is normally a matter of comparison of the observed behaviour(s) to the known, typical effects of fatigue, as well as other potential contributing factors. If a person’s performance impairment was related to information processing, decision-making, attention, mood, or reaction time, then it is possible that fatigue played a role.
Regardless of its source, fatigue in individuals who are responsible for transportation safety is a risk that needs to be understood and mitigated. As many transportation industries operate around the clock, fatigue and its effects cannot be eliminated completely; however, it must be managed. A first step in this process is for TSB investigators to document the prevalence and role of fatigue in transportation accidents that occur. To assist, the TSB has just released the Guide to investigating sleep-related fatigue, which contains the fatigue data collection and analysis tool. Please contact us for more information on fatigue, or to request a copy of the Guide. You can email us at firstname.lastname@example.org or call 1-800-387-3557 (extension 2).
Christina (Missy) Rudin-Brown has been a Senior Human Factors Investigator with the TSB since 2012. She has been studying the effects of human factors issues – such as impairment from fatigue, distraction, drugs and alcohol – on operator behaviour in a variety of transportation modes for over 20 years. She lives in Ottawa with her husband and three daughters and, in her spare time, loves to travel and stay fit.
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