Preparing drivers for planned control transitions in automated cars

In the near future we expect automated driving to be available for specific segments of a journey, e.g., when driving on the highway. At the end of such a route segment, a (planned) control transition from system to driver occurs. While immediate (unpredictable) take-over situations are heavily investigated, there is still a gap in understanding how to present planned take-over requests, especially while drivers might be involved in non-driving-related activities (NDRAs). We investigated the effect of three different visual representations to indicate planned take-over requests (TOR) on usability, comfort, and driving quality. Additionally, we explored the influences of different NDRAs and the device used for this activity. The results of our simulator study (N=24) indicate that (1) upcoming take-over requests should be displayed dynamically, (2) preferred devices depend on the performed task and (3) take-over requests should be presented with auditory, visual, and tactile cues. Based on our findings, we contribute design recommendations to support the development of safe and comfortable planned control transitions.