Fatigued Workers: 5 Influencing Factors

Drowsy Driving and Fatigue
New research from the AAA Foundation suggests that driver fatigue is involved in 20% of all fatal accidents (AAA Foundation, 2014). This finding is based on a representative sample of 14,268 crashes that occurred between 2009 – 2013.

This statistic is dramatically higher than the 2.5% incidence rate that was reported by the National Highway Traffic Safety Administration in 2011. The actual incidence rate is challenging to pinpoint, due to discrepancies in data collection methods; however, fatalities in fatigue-related accidents has been estimated to be around 15-33% (Masten, Sutts, & Martel, 2006; Tefft & AAA Foundation, 2010).

According to a 2011 study by the Centers for Disease Control and Prevention of almost 75,000 adults, 38% reported inadvertently falling asleep during the day at least once in the past month and 4.7% reported nodding off or falling asleep while driving at least once in the past month.

These microsleeps, which generally last anywhere from 2 to 20 seconds, can result in devastating consequences for an employer in terms of loss of life, injuries, and financial implications.
Below we cover five major factors that can influence the likelihood of a fatigue-related accident taking place.

Five Influencing Factors

1. Time of Day

Night workers are 3x more likely to have a fatigue-related driving accident. Previous research has found he highest number of fatigue-related accidents occur between the hours of midnight and 6 AM, as shown in Figure 1. (AAA study, J. Stutts, UNC 1999).

It’s important to note that serious fatigue-related accidents can occur at any point in the day, at high noon on a sunny day.

 Figure 1: Fatigue Related Accidents vs Time of Day

2. Hours Awake

After being awake for over 18 hours, an individual’s degree of cognitive impairment is equivalent to someone with a 0.08% blood alcohol concentration (BAC), which is double the legally intoxicated limit for commercial driving purposes. Impairment rises to an equivalent BAC of 0.10% after 24 hours of sustained wakefulness (Williamson & Feyer, 2000).

3.Underlying Sleep Disorders

Untreated sleep disorders, like obstructive sleep apnea, can significantly increase the likelihood of a fatigue-related accident.

Studies have shown that individuals with obstructive sleep apnea (OSA) have a 40% increased rate of daytime sleepiness (Ulfberg, 1996) and 2x as many traffic accidents per mile as individuals without OSA (Horstmann, 2000).

CIRCADIAN’s databases (containing data from more than 10,000 shift workers) show that 11% of shift workers have OSA and 15% display key symptoms of OSA or other sleep disorders related to excessive sleepiness.

4.Rotating vs Fixed Shift Schedules

Workers with rotating shifts are twice as likely to have a fatigue-related driving accident as compared to workers on fixed shift schedules (AAA study, J. Stutts, UNC 1999).

Shift schedules that don’t allow for adequate rest periods between shifts can also increase the likelihood of a fatigue-related accident.

5.Adjustment to Shiftwork Lifestyle

Non-adapted shiftworkers report feeling drowsy and nodding off while working three times more often than adapted shift workers, and making mistakes and errors four times more often (CIRCADIAN, 2003).

Preventing Drowsy Driving

There are strategies that can be implemented to reduce the risk of drowsy driving among company drivers, such as:

  • Fatigue management software
  • Shift schedule optimization
  • Managing a shiftwork lifestyle training
  • Fatigue countermeasures
  • Sleep Disorder Screenings

Many companies have experienced dramatic benefits in terms of decreased accident rates, costs, and increased employee retention after implementing fatigue risk management solutions.


Nine months after implementing CIRCADIAN fatigue risk management solutions, Dupre’ Logistics had the following results:
  • 89% reduction in fatigue-related accidents
  • Over $1 million saved in accident-related costs
  • 50% reduction in driver turnover and absenteeism
Learn More About Dupre' Logistics Story

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Managing Driver Fatigue: A Risk-Informed, Performance-Based Approach

Managing Driver Fatigue


CIRCADIAN® is the global leader in providing 24/7 workforce performance and safety solutions for businesses that operate around the clock. Through a unique combination of consulting expertise, research and technology, software tools and informative publications, CIRCADIAN helps organizations in the 24-hour economy optimize employee performance and reduce the inherent risks and costs of their extended hours operations.

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