Establishing a fatigue risk profile
Tuesday, November 18, 2014 by Chris Hocking
Conventional strategies to mitigate the effects of fatigue in shift-working 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 shift work. People don't adapt to shift work, 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 upon which to make informed decisions tailored to the unique operational needs of the site.
Optalert's products use the only safety system in the world continuously providing real-time objective, scientifically-validated alertness information to both drivers (in cab) and supervisors (through Optalert's Individual Risk Indicator System (IRIS™). The continuous flow of information offers multiple 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.
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
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 (7am, 7pm) with peak risk observed during the early hours of the morning (3am – 5am). 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.
Keep in mind however, a company’s shift roster design can influence the times of the day when fatigue-related risk is greatest.
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.
Evaluating shift roster design
With the generated fatigue risk profile, the data can be further analysed to evaluate all aspects of a company’s shift roster to identify areas of risk within the system specific to the operational environment and shift design in use. These can include evaluations of; shift duration, start and end times, scheduling of breaks, roster cycles, and scheduling over time.