To examine the relationship between heavy vehicle driver fatigue, time of day and shift-start times, data from an automatic driver monitoring system (Guardian, Seeing Machines) was assessed for over 140,000 shifts across four different operator companies. Results revealed that of the 2290 fatigue events detected, 63% occurred during the night time (between 6pm – 6am). Higher rates of fatigue events were also observed for shifts that started in the afternoon (12pm – 6pm) and evening (6pm – 12am) compared to those starting in the morning (6am – 12pm). Furthermore, shifts that started in the afternoon and evening were associated with earlier onset of fatigue. These results are consistent with the deleterious circadian influence on alertness at night and demonstrate the potential for using alertness monitoring to evaluate the impact of shift schedules on fatigue. Adjusting schedules based on such objective alertness data has the potential to mitigate the impact of fatigue
