Effect of prolonged periods of conditionally automated driving on the development of fatigue: with and without non-driving-related activities

Abstract

Due to the ongoing development in automated vehicle technology, conditionally automated driving (CAD) will become a realistic scenario within the next years. However, an increasing automation in driving tasks and taking the driver out of the loop increases the risk of monotony and fatigue brought on by boredom. Whether the driver is still able to take over the vehicle guidance at system limits is questionable. Therefore, the aim of the current driving simulator study is to investigate how prolonged monotonous periods of conditionally automated driving affect passenger fatigue level and the take-over performance and how both is affected by voluntary non-driving-related activities (NDRA). For this purpose, two conditions (encouraging fatigue and encouraging alertness by engaging in voluntary NDRA) were tested in a 60 min conditionally automated drive followed by a take-over situation. Twenty-five percent of the participants in the fatigue encouraging condition temporarily showed strong evidence of fatigue or they fell asleep. However, the time of occurrence of fatigue phases varied among individuals (occurrence mainly after 20–40 min of automated driving). The take-over performance in the take-over situation after 60 min of CAD did not deteriorate in the fatigue condition compared to the alertness condition.