Driver impairment at night and its relation to physiological sleepiness

Abstract

Anund A, Kecklund G, Peters B, Forsman Å, Lowden A, Åkerstedt T. Driver impairment at night and its relation to physiological sleepiness. Scand J Work Environ Health. 2008;34(2):142-150.Objectives Studies of devices detecting sleepiness need reference points of physiological sleepiness. The present study sought to validate the Karolinska drowsiness score (KDS) as an indicator of physiological sleepiness against driving impairment and eye blink duration during a 45-minute drive in an advanced moving-base driving simulator.Methods Data from 19 persons were used in the analysis. Electrooculography, electroencephalography, and electromyography were administered continuously. Physiological sleepiness was quantified by scoring the percentage (0-100%) of the scoring epoch with alpha and theta activity and slow eye movements (KDS). Lateral position and speed were used as measures of driving behavior. Lane departure was defined as two wheels touching the lane markers. Blink duration was used as a secondary indicator of sleepiness. ResultsThe results showed that, for young drivers, sleepiness increased with time in the task with higher levels.The variability of the lateral position and the mean and variability of the blink duration significantly changed when sleepiness increased to KDS ≥20%. Furthermore, there was an increase in the risk of lane departure for KDS ≥30%. ConclusionsThe results suggest that KDS scoring is a reasonable procedure for estimating physiological sleepiness under conditions of driving. The results also indicate that a younger age is associated with greater sensitivity to sleepiness at the wheel.

The Effects of Driving Situation on Sleepiness Indicators after Sleep Loss: A Driving Simulator Study

“…It responded very clearly to sleep loss, as well as to time on task. The pattern is very similar to that of other studies using the same scale (KSS) [8][9][10] , but again, the peak levels in the present study was about one unit lower than the usually encountered level 9.…”

“…This is rather remarkable, considering all the studies that show severe effects of sleep loss on eye blinks 10,11,14) . There doesn't seem to exist any comparable data but in a study of effects of time of day on the risk of different types of crashes it was found that the only type of crash without a late-night peak in relative accident risk was that due to overtaking 20) .…”

“…Sleep loss appears to have had the expected effects on sleepiness indicators 10,11,14) . Following another car did not affect sleepiness, which had been hypothesized.…”

“…The study wasn't sufficiently large to take into account age and gender and we have found a tendency of younger subjects to be more sleepy 10) and males seem more at risk in terms of night time crashes (controlling for alcohol) 20) . However, it is not clear how this would have affected the results, even if one could speculate that younger males might benefit more from a more variable driving context.…”

The alerting effect of hitting a rumble strip—A simulator study with sleepy drivers

“…The measurement of driver sleepiness normally involves indicators such as the standard deviation of the lateral position (O'Hanlon and Kelly, 1974;Otmani et al, 2005), frequent subjective ratings of sleepiness during driving (Åkerstedt et al, 2005;Anund et al, 2008b;Ingre et al, 2006a) the electroencephalogram (EEG) with its content on alpha band (8-12 Hz) and theta band (4-8 Hz) activity (Horne and Reyner, 1996;Gillberg et al, 1996) as well as the electrooculogram (EOG). The latter may involve increased duration of eye blinks (Dinges et al, 2005) or slow rolling eye movements (Åkerstedt and Gillberg, 1990).…”