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 multiplied by 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 industrial driving tasks.