  Vehicle pedestrian communication is extremely important when developing
autonomy for an autonomous vehicle. Enabling bidirectional nonverbal
communication between pedestrians and autonomous vehicles will lead to an
improvement of pedestrians' safety in autonomous driving. If a pedestrian wants
to communicate, the autonomous vehicle should provide feedback to the human
about what it is about to do. The user study presented in this paper
investigated several possible options for an external vehicle display for
effective nonverbal communication between an autonomous vehicle and a human.
The result of this study will guide the development of the feedback module in
future studies, optimizing for public acceptance and trust in the autonomous
vehicle's decision while being legible to the widest range of potential users.
The results of this study show that participants prefer symbols over text,
lights and road projection. Additionally, participants prefer the combination
of symbols and text as interaction modes to be displayed if the autonomous
vehicle is not driving. Further, the results show that the text interaction
mode option "Safe to cross" should be used combined with the symbol interaction
mode option that displays a symbol of a walking person. We plan to elaborate
and focus on the selected interaction modes via Virtual Reality and in the real
world in ongoing and future studies.
