Managing fatigue-related risk: an accident waiting to happen

Managing fatigue-related risk is one of the biggest safety issues facing industries where shiftwork is a necessary component of operations. Industries operating around the clock require various types of shift schedules to maintain 24/7 operations. Work schedules involving long and irregular hours, night work or rotating shifts significantly affect the time available and opportunity for sleep. Around-the-clock operational demands in these industries challenge the body’s natural cycle of waking and sleep.

The most common health problem reported by an estimated 75% of shift workers is disturbed sleep. It only takes one week of poor quality or restricted sleep to induce performance impairment equivalent to having a blood alcohol concentration of 0.1, significantly increasing the risk of an accident. It is not surprising then that up to 30% of serious accidents are directly related to fatigue.

The performance impairments attributable to fatigue not only make people less effective but also very unsafe. Numerous studies have found a relationship between fatigue and work-related injuries. Excessively sleepy or fatigued workers are 70% more likely to be involved in industrial accidents than alert, well-rested individuals.

Most shiftworking industries are required to identify, assess and control fatigue as part of their health and safety management system. However, the management of fatigue-related risk in 24-hour operations is a complex and challenging issue. This particularly applies to personnel working in hazardous environments or performing safety critical tasks, such as commercial truck drivers or heavy vehicle operators in the road transport and mining industries.

Any fatigue risk management plan must take into account working time arrangements, which typically include:

• Scheduling of rosters
• Number of consecutive shifts
• Types of shift
• Maximum hours per shift and per roster cycle
• Break patterns within and between shifts
• Allowances for overtime scheduling
• Commuting time to and from work

There are countless variations of shift patterns, with varying combinations of shift duration (eg, 8 h, 12 h), shift types (eg, day, evening, night) and roster cycles. For instance, a survey of Australian coal mining workers found more than 70 distinct patterns of shiftwork.

With the known performance impairments associated with fatigue, the variability of shift rostering designs complicates the risk management of fatigue, both from fitness for work and roster design perspectives. Valid and objective data is required to determine the degree to which a company’s shift roster design, or changes therein, impacts on fatigue-related risk.

Conventional strategies to mitigate the effects of fatigue in shiftworking occupational settings, particularly in the transport and mining industries, are primarily centred on regulatory and organisational approaches. These include limits to hours of duty, education and training. Such approaches are essential and have positive effects on workplace alertness, safety and productivity. However, there are numerous limitations to the effectiveness of these approaches as fatigue is a common and unavoidable by-product of shiftwork. People don’t adapt to shiftwork, particularly evening work, night work and rotating shift schedules. Without the ability to objectively measure fatigue, it is almost impossible to effectively manage the associated risks.

Using technology to reduce fatigue-related risk

The use of objective data to quantify fatigue levels of specific groups of drivers/operators allows companies to mitigate their exposure to fatigue-related risk by tailoring working time arrangements to suit particular operational settings. Technology can provide companies with the necessary objective information to evaluate all aspects of their shift roster design by identifying areas of risk specific to the operational environment. Objective information then forms the basis on which to make informed decisions tailored to the unique operational needs of the site.

The Optalert safety system continuously provides objective, scientifically validated alertness information to both drivers and supervisors in real time. The continuous flow of information offers two layers of protection against the dangers of fatigue and allows all parties to monitor the associated risk and initiate proactive measures before it reaches dangerous levels.

Mining and road transport organisations are using the information provided by Optalert to quantify the impact of fatigue on their operations. This objective data is being used positively as a tool for reinforcing operational decisions such as changes in tasks, shift-rotations, break times and timing of appropriate fatigue countermeasures. Over time, the data can be used to profile the overall fatigue-related risk of an entire operation. Quantifying changes in risk provides objective evidence regarding the effectiveness of a company’s fatigue risk management policies and procedures over periods of months or even years.

The fatigue-risk profiles from 24-hour operations typically resemble the circadian rhythm of alertness. This is characterised by increased risk during night shift, particularly during the early hours of the morning. This time of day also aligns with the low point in the circadian rhythm of core body temperature when the body is most in need of sleep. These circadian patterns are consistent with the known relative risk of truck fatalities for each hour of the day illustrated below.

Figure 1. Relative risk of fatal truck accidents by time of day. The yellow line represents the circadian variation of core body temperature. Source: Viewpoint - Perspectives on Modern Mining, 2007, Issue 2, pg 29.  Caterpillar Global Mining.

Establishing a fatigue risk profile

To illustrate how Optalert data is being used by mine sites to develop a fatigue risk profile, consider the following graphs depicting alertness levels and frequency of fatigue warnings from 238 mine haulage vehicle operators working on a roster of 12-hour day and night shifts over several months. This involved more than 103,000 hours of objective data (Figure 2).

Figure 2. Average alertness levels (left graph) recorded from 238 drivers during day shifts and night shifts (blue-shaded region) for a total of 6.2 million fatigue scores. The frequency of in-cab Optalert warnings (medium and high risk) per hour of driving (right graph) issued to the same drivers.

The fatigue risk profile for this fleet of mine haulage drivers indicates the lowest levels of risk are observed at the beginning of day shift and night shift (7 am, 7 pm) with peak risk observed during the early hours of the morning (3 am-5 am). While specific areas of risk are highly influenced by shift roster design, the overall patterns of these profiles often follow a strong circadian variation of alertness throughout the day.

Evaluation and optimisation of shift roster designs

Once the initial fatigue-risk profile has been generated, the data can be further analysed to evaluate all aspects of a company’s shift roster design to identify areas of risk within the system specific to the operational environment and shift design in use.

The value of objective data is not only confined to evaluating existing shift roster designs, but can also be used to make evidence-based changes to an existing system and quantify the effectiveness of these changes over time.

Tailoring shift roster design to suit unique operational environments will mitigate exposure to fatigue-related risk while maintaining operational flexibility.

*Dr Andrew Tucker is the General Manager Scientific Research at Optalert Australia Pty Ltd. He has a PhD in psychology and psychophysiology investigating aspects of visual perception, attention and oculomotor function. He has been instrumental in the development of Optalert’s wearable technology and validation of the Johns Drowsiness Scale (JDS), alongside Optalert founder Dr Murray Johns.