Drivers’ Individual Design Preferences of Takeover Requests in Highly Automated Driving

Abstract

Highly automated cars will be on the worlds’ roads within the next decade. In highly automated driving the vehicle’s lateral and longitudinal controls can be passed on from the driver to the vehicle and back again. The design of a vehicle’s take-over requests will largely determine the driver’s performance after taking back vehicle control. In the scope of this paper, potential drivers of highly automated cars were asked about their preferences regarding the human-machine interface design of take-over requests. Participants were asked to evaluate eight different take-over requests that differed with respect to (a) take-over request procedure (one-step or two-step procedure), (b) visual take-over request modality (text or text and pictogram), and (c) auditory take-over request modality (tone or speech). Results showed that participants preferred a two-step procedure using text and speech to communicate take-over requests. A subsequent conjoint analysis revealed that take-over requests ideally use speech output in a two-step procedure. Finally, a detailed evaluation showed that the best take-over request interface received significantly higher user experience ratings regarding product characteristics as well as users’ emotions and consequences of product use than the worst take-over request interface. Results are related to the background literature and practical implications are discussed.