Abstract
A lack of task workload can lead to drivers’ cognitive fatigue and vigilance decrement during a prolonged drive. This study examined the effects of speed variability on driving fatigue in a monotonous drive. Twenty-one participants participated in a 60-min simulated driving task. All participants’ cognitive fatigue was assessed using psychological and physiological measurements. Results showed that among all participants, variability of vehicle speed was negatively correlated with sleepiness and hypo-vigilance during the driving task. Further, drivers in the large variability group reported less sleepiness, less fatigue, and more vigilance than those in the small variability group did during the driving task. These drivers also presented a smaller electroencephalogram spectral index (𝜃+α)/β during the task, where 𝜃, α, and β are the power spectra of three different frequency bands: theta (𝜃, 4∼8 Hz), alpha (α, 8∼13 Hz), and beta (β, 13∼30 Hz). Our findings suggested that the larger variability of speed within the speed limit may have a deterrent effect on drivers’ cognitive fatigue.
Highlights
Over 1.2 million people are killed in the traffic accidents each year around the world, with millions of people suffering from severe injuries and living with long-term adverse health consequences (World Health Organization, 2015)
Results suggested that participants with greater speed variability reported to be less sleepy and more vigilant after the monotonous driving task
Results indicated that participants having larger pupil diameters during segment 3 of the driving task reported to be less sleepy, less tired, and more vigilant
Summary
Over 1.2 million people are killed in the traffic accidents each year around the world, with millions of people suffering from severe injuries and living with long-term adverse health consequences (World Health Organization, 2015). Driving is considered a vigilant task, in which the driver needs to maintain a high level of alertness. For task-related fatigue, cognitive overload commonly is induced by high task demands requiring sustained attention; prolonged driving that offsets driver workload can benefit such form of task-related fatigue. Cognitive Fatigue and Speed Variability cognitive underload is induced by continuous and monotonous driving conditions, which require an increased task novelty and demand to reduce this form of task-related fatigue (Hancock and Warm, 1989; Thiffault and Bergeron, 2003; Saxby et al, 2013). Once the demands of driving become more familiar and monotonous, the driver is more vulnerable to reach an underload state. A monotonous prolonged drive requires more attentional resources that cause driver vigilance. A monotonous driving task represents reduced task effort, causing boredom and fatigue
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