The study was designed to examine the effects of extra task stimulation and extra rest on performance and fatigue of haul truck drivers engaged in a simulated driving task. Sixty male subjects, randomly selected from the population of truck drivers in a large mining company, operated a driving simulator for a period of 7 h. A 2 x 3 experimental design was employed including two levels of rest conditions and three levels of secondary-task manipulations. The results show that performance and perceived fatigue were significantly higher when a secondary task involving voice communication was added to the basic driving task, but an added vigilance task had less effect. An extra 30-minute rest period in the middle of the experimental session significantly alleviated the reported experience of fatigue but did not affect performance. The results are discussed in terms of their relevance to actual in-dustrial driving tasks. Like many other behavioral phenomena, fatigue has been defined in numerous ways by different researchers. As McFarland (1968) wrote: "Definitions of the nature of fatigue are almost as numerous as the articles that have been written about it, since each de-pends largely upon the interests or technical background of the author. " One of the more comprehensive definitions of fatigue was of-fered by Wolf (1967), and Saito, Kogi, and Kashiwagi (1970), who, in their factor ana-lytic studies, reported that the sensation of fatigue has three major components: (1) the sensation of bodily tiredness and drowsiness, (2) the sensation of weakened motivation or concentration towards the task, and (3) a group of physical complaints pertaining to

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Based on Coroners ' verdicts, fatigue of car or truck drivers was a contributing factor in 9.1 % of fatal accidents involving trucks. Based on the presence of factors such as extended driving hours, falling asleep at the wheel, comments about tiredness, driving right of centre and night-time driving, the authors estimated fatigue contributed to 19.9 % of the accidents. There were approximately equal numbers of fatigued car drivers and truck drivers. An analysis of casualty and fatal truck accidents by time of day (adjusted for exposure) showed that accident risks were highest during the night on all five Victorian highways studied. Driver fatigue is one of the possible factors underlying this pattern of elevated risk. The report section described in-vehicle fatigue counter-measures. The distinction between fatigue monitors and alerting devices was made and it was recommended that eye closure and head nodding monitors and an alerting device be tested in the next stage of this project. Key Words: Fatigue (human), accident rate, fatality,

Proceedings of the

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