A Comparison of Concepts for Control Transitions from Automation to Human

Until upcoming autonomous vehicles can handle every scenario in all operation domains there will be situations, in which the human driver needs to retrieve control of the vehicle. This can lead to safety issues as literature shows impaired driving performance after taking over from highly automated driving. A discrete switch of control might be a valid option to hand over to an attentive human driver. However, it is questionable if this is a safe way for a transition of control to somebody who is distracted at the time of the takeover request. Instead, gradually shifting control via a period of haptic shared control can provide guidance during the process of establishing situation awareness. Here, we present different design concepts for handing over control from a controller to a human partner. To analyze these concepts, we designed an experiment, in which the participants need to take over a simplified steering task when requested by the automation. We conducted a study comparing two discrete switching transitions and three concepts in which the authority of the controller fades out slowly. The results show that in situations, needing a continuation of the control action of the automation, an early switch-off underperformed compared to the other concepts. If the situation demanded action during the transition the shared control approaches achieved the lowest tracking error. A survey of the participants revealed that gradually shifting transitions lead to a sense of better performance and are also regarded as more comfortable. The best overall results were obtained by a concept which models human behavior and considers it within the takeover process. This approach provides a systematic method for the design of authority transitions by finding the best trade-off between guidance and handover.