How do prolonged wakefulness and alcohol compare in the decrements they produce on a simulated driving task?

The effects of alcohol ingestion were compared with those of prolonged wake fulness on a simulated driving task. Eighteen healthy, male subjects aged b etween 19 and 35 years drove for 30 min on a simulated driving task at bloo d alcohol concentrations of 0.00, 0.05 and 0.08%. Subjective sleepiness was assessed before and after the driving task. Driving performance was measur ed in terms of the mean and standard deviation (S.D.) of lane position (tra cking); the mean and S.D. of speed deviation (the difference between the ac tual speed and the posted speed limit); and the number of off-road occurren ces. Ratings of sleepiness increased with increasing blood alcohol concentr ation, and were higher following the driving task. With increasing blood al cohol concentration, tracking variability, speed variability, and off-road events increased, while speed deviation decreased, the result of subjects d riving faster. The results were compared with a previous study examining si mulated driving performance during one night of prolonged wakefulness [Arne dt, J.T., MacLean A.W., 1996. Effects of deep loss on urban and motorway dr iving stimulation performance, Presented at the Drive Alert... Arrive Alive International Forum, Washington DC], using an approach adopted by Dawson a nd Reid [Dawson, D., Reid, K., 1997. Fatigue, alcohol and performance impai rment. Nature 388, 23]. For mean tracking, tracking variability, and speed variability 18.5 and 21 h of wakefulness produced changes of the same magni tude as 0.05 and 0.08% blood alcohol concentration, respectively. Alcohol c onsumption produced changes in speed deviation and off-road occurrences of greater magnitude than the corresponding levels of prolonged wakefulness. W hile limited to situations in which there is no other traffic present, the findings suggest that impairments in simulated driving are evident even at relatively modest blood alcohol levels, and that wakefulness prolonged by a s little as 3 h can produce decrements in the ability to maintain speed and road position as serious as those found at the legal limits of alcohol con sumption. (C) 2001 Elsevier Science Ltd. All rights reserved.