Automated Driving causes new demands on human's abilities in contrast to manual driving. Especially in SAE Level 2 the driver has to pay permanent attention to take over vehicle's control immediately. Regarding basic research in psychology, humans are not able to maintain permanent attention (their vigilance) in long monotonous situations, because of so called passive task related fatigue. However, Level 3 driving functions do not require human's permanent attention: The driver is allowed to perform tasks unrelated to driving but has to be available as a fallback ready user within a time buffer. Research questions focused on the representation of driver's fatigue in a real driving scenario as well as on the compensatory potential of a Level 3 driving function to prevent fatigue symptoms. Two test drives were performed to measure long-term effects of automated driving on driver's state, particularly on fatigue. A total sample (net) of 49 participants went through a onehour drive in a Wizard-of-Oz vehicle using a monotonous test track. Here, the examination focused on the objective and innovative measurement of fatigue with electroencephalography (EEG), in particular by alpha spindles. In the first experiment one group of participants used a very reliable driving function, whereas failures in lateral- as well as longitudinal control occurred for another group. This design allowed to investigate driver's state depending on the driving duration and Level 2 functional reliability. In the second experiment (within subject design) all participants went through transitions between Level 2 and Level 3 after approx. 30 minutes driving to compare driver state in Level 2 and Level 3 directly. This complex and innovative research approach claims the combination of experimental control with high external validity and took place in the course of the BMWI-funded project "Ko-HAF" (Cooperative Highly Automated Driving). Participants which were classified as "got tired" with the aid of alpha spindles in the first experiment showed a monotonous increase of fatigue in the first 20 minutes of driving, whereby more than 66% of variance in fatigue intensity could be explained solely by the driving duration. Reliability of Level 2 had no significant effect on intensity of fatigue. Nevertheless, reaction times of participants increased significantly when crossing a lane after approx. 50 minutes of driving, if they were classified as "got tired" or went through a very reliable Level 2 drive before. The second experiment revealed significantly reduced fatigue in a Level 3 compared to the same duration of Level 2 (in each case within 25 minutes of driving), because in Level 3, all participants were unburdened from the task of monitoring and were allowed to perform motivating tasks unrelated to driving.
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