Sleep inertia in automated driving: Post-sleep take-over and driving performance

•Take-over performance and manual driving behavior are investigated in drivers after electroencephalography-confirmed stable sleep..•After sleep, take-over performance is impaired yielding “driving errors” in the Take-Over Controllability-Rating.•Manual driving performance after sleep yields impairments in lane and speed keeping and drivers chose lower speeds.•Sleep inertia has a serious impact on driving behavior and has to be accounted for in the development of automated vehicles. Sleep is emerging as a new driver state in automated driving. Post-sleep performance impairments due to sleep inertia, the transitional phase from sleep to wakefulness that can take up to 30 min, are a potential safety issue. Take-over performance immediately after sleep is impaired and drivers perceive the take-over as critical. The aim of the presented study was to assess take-over behavior immediately after sleep and driving behavior during the 10 min after sleep. A study with N = 31 drivers was conducted in a high-fidelity driving simulator. Take-over performance and driving performance were assessed a) under alert baseline conditions and b) after awakening from electroencephalography-confirmed stable sleep. Take-over performance 15 s after awakening was impaired resulting in more driving errors compared to the alert baseline. Lane keeping was dramatically impaired in the first 3 min after sleep and recovered rapidly. Drivers drove slower after sleep and speed keeping was less stable for at least 10 min. The results suggest that human-machine interaction design should account for the drivers’ impaired post-sleep driving performance.