Wake Up and Take Over! The Effect of Fatigue on the Take-over Performance in Conditionally Automated Driving

Although fatigue's negative impact on driving performance is well known from manual driving, its effect on the take-over performance during the transition from conditionally automated driving to manual driving is still uncertain. The effect of fatigue on the take-over performance was examined in a driving simulator study with 47 participants assigned to two conditions: fatigued or alert. In the corresponding condition (fatigued or alert), the desired driver state was promoted by specific measures (e.g, daytime, caffeinated beverages, physical exercise). In the fatigued condition, the take-over situation was triggered once participants reached a certain high level of fatigue. Two trained, independent observer assessed fatigue with the support of a technical fatigue assessment system based on objective eyelid-closure metrics (e.g, PERCLOS). In the alert condition, participants drove conditionally automated for a fixed 5-minute period. Results showed no significant difference between participants' take-over times in the two conditions. However, fatigued participants were significantly more burdened and stressed during the take-over situation than were alert participants and manifested less confident behavior when coping with the situation. This behavior may negatively affect the transition from conditionally automated driving to manual driving in more complex situations and merits further examination.