Fatigue and driving

What is fatigue? Subjective experience of sleepiness, tiredness, lack of energy that cause decrease in performance and arousal. Five dimensions: Lack of energy Physical exertion Physical discomfort Lack of motivation Sleepiness

What is fatigue? Fatigue is NOT equal to lack of sleep Even after a full night sleep a monotonous driving task can lead to fatigue Both being overload ( situational demands are higher than the fitness of the driver) and underload ( situational demands are lower than the fitness of the driver) can lead to fatigue among drivers (Oron-Gilad et al., 2002)

Effects of fatigue on driving Fatigue especially impair attention and vigilance of drivers Slower reaction times Difficulty in estimation of speeds and headways Reduced attention to road signs Crossing a traffic light without noticing its color

Fatigue and accidents The 2.7% of all fatal accidents occured due to fatigue, sleepiness and ilness in the US (NHTSA, 2009) Fatigue related accidents are underestimated because it is more difficult to detect fatigue

Sagberg, 1999

Objective mesaures of fatigue Sleep deprivation Not having enough sleep Decrease detection of peripheral targets (Roge et al., 2003) Circadian rhythm Natural cycle of wakefullness Sleepiness is greatest between 2am and 6am and increase slightly again early afternoon Especially long-disrtance drivers who drive at nights and young drivers have more fatigue related crashes

FMCSA, 2009

Objective mesaures of fatigue Hours of driving As the hours of driving increase, drivers showed a reduced detection to the targets that deviated from the center of the visual field (Roge et al., 2003) Distance driven Longer distances increase the likelihood of fatigue-related crashes

Physiological indicators of fatigue EEG recordings increase in alpha and theta waves indicates fatigue Blinking behavior When fatigued blink rate increases and amplitude of eye opening decrease Heart rate variability

Fatigue and crash involvement It is hard to assess the contribution of fatigue to crashes but fatigue related crashes are: more severe and fatal crashes especially the ones on dark and rural roads more likely to be running off the road crashes more likely to happen early morning hours more likely to involve long vehicles

Fatigue and crash involvement Fatigue vs alcohol Effect of approximately hours of sleep deprivation on driving performance is equivalent to the effect of 0.10% alcohol

Risk groups for fatigue-related crashes Males Young drivers Drivers with untreated and unrecognized sleep disorders E.g., insomnia, sleep apnea, narcolepsy... Shift workers Professional drivers

Fatigue countermeasures Management of sleep, and napping On long trips having short naps (10-20 minutes) is a effective way Drivers’ behavioral strategies. For example, Listening to radio Talking to a passenger Drinking a coffee… Sometimes driver need to increase their cognitive load

Fatigue countermeasures Drinking coffee Most effective when combined with a short nap Environmental countermeasures Providing drivers with rest areas Putting rumble stripes to the road to reduce drive-off-the road crashes Fatigue detection and warning systems in the cars