Understanding the Headless Rider: Display-based Awareness and Intent-Communication in Automated Vehicle-Pedestrian Interaction in Mixed Traffic

Automated vehicles do not yet have clearly defined signaling methods towards other road 9 users, which could complement natural communication practices with human drivers, such as eye 10 contact or hand gestures. In order to establish trust, external Human-Machine Interfaces (eHMI) 11 have been proposed, but so far these have not been widely evaluated in natural traffic contexts. This 12 paper presents a user study where 30 participants interacted with a functional display-based visual 13 eHMI for an automated shuttle in mixed urban traffic. Two distinct features were investigated: the 14 communication of (1) its awareness of different obstacles on the road ahead and (2) of its intention 15 to start or to brake. The results indicate that the majority of participants in general regarded eHMIs 16 as necessary for automated vehicles. When reflecting their experience with the eHMIs, about half of 17 the participants experienced an increased comprehension and safety. Combined presentation of ob-18 stacle awareness and vehicle intentions helped more participants to understand the shuttle´s behav-19 ior than the presentation of obstacle awareness only, but fewer participants regarded this combina-20 tion of awareness and intent to be safe. The strength of the found effects on subjective responses 21 varied with regards to age and gender.