We investigated the impact of automated driving phases of different durations (long vs. short) on take-over performance and driver state. Thirty participants drove on a dynamic simulator under autonomous mode for three successive periods of automated driving: a short (10 min), a long (1 hour) and another short (10 min) period, each ending with a take-over request. They performed a non-driving task, watching a film of their choice, throughout the autonomous phases. Driving performance -reaction time and quality -and driver drowsiness were assessed at each take-over. One hour of automated driving affected the driver's behaviour, leading to poorer take-over performance (longer reaction time and sharper avoidance manoeuvre) and increased drowsiness compared to a shorter autonomous period. Results also suggest that sequencing the autonomous phase in several short periods should improve the driver's take-over performance and help prevent drowsiness. Our findings sound a warning on the risks associated with long phases of automated driving. In particular, we provide evidence that series of short periods of automated driving are preferable to a long, continuous automated driving phase.