From Sleep Mode to Drive Mode: Take-Over after Sleep Takes Minutes not Seconds

SAE Level 4 automated vehicle systems may allow drivers to nap while driving. The aim of this study was to investigate the natural take-over time after a nap without external time pressure. Nine subjects completed a total of 33 test drives in the Fraunhofer IOSB driving simulator, with take-over time measured as the time between the alarm sounding and the manual deactivation of autonomous mode. The average take-over time was 1.5 min after a nap, with a max of about 3.5 min. The results highlight the importance of sufficient time for a stress-free take-over process after sleep, which is far beyond the Level 3 standard of 10 s.