We investigated the impact of automated driving phases of different durations (long vs. short) on takeover 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 takeover 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 takeover. One hour of automated driving affected the driver's behaviour, leading to poorer takeover 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 takeover 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.