Morning chronotypes and post-lunch dip: an investigation of driving fatigue in well-rested subjects

The current literature lacks comprehensive knowledge regarding the relative and combined effects of task-related factors, such as driving in monotonous environments, and the 'post-lunch dip'-n afternoon bi-circadian increase in sleepiness-particularly within a specific chronotype group. This study aims at investigating the impact of post-lunch driving and time-on-task on fatigue and performance among well-rested morning-type individuals during simulated driving. Twelve male participants with a morningness chronotype completed a series of lane change test simulated driving tasks, comprising three 20-minute blocks both before and after lunch. The results demonstrated a significant main effect of the 'post-lunch dip' on reaction time, alertness, and self-reported sleepiness. However, neither the time spent on the task nor the interaction between sleep- and task-related factors yielded significant effects on the measured variables. Furthermore, medium to high correlations among all pairs of measures suggest a good agreement for detecting fatigue and sleepiness in driving tasks.