Assessing the combined effects of task factors and sleep need on driving

Driver fatigue has been attributed to both sleep need and to task-related factors, including time-on-task. The current simulator study examined the sleep-task interaction to determine their relative contributions to fatigue. Sixty participants were randomly assigned to two sleep conditions (shorter vs. longer) before a 2-hour drive. In addition to time-on-task, cognitive task load (higher vs. lower) was also manipulated as a task-related factor. Significant effects of sleep restriction and time-on-task were observed on performance (lane position variability – SDLP) and subjective ratings (sleepiness, alertness, effort). The implications for understanding driver fatigue are discussed.