Towards a Universal Explicit Communication Design of External Human-Machine Interfaces (eHMI) for Differently Sized Highly Automated Vehicles Evaluated by Different Pedestrian Age Groups

Abstract

This research deals with the design of external human-machine interfaces (eHMI) for two differently sized highly automated vehicle types (passenger car vs. bus) focusing on the interaction between highly automated vehicles (HAVs) and pedestrians of different age groups. Research has shown that at least in some situations HAVs need to be able to communicate explicitly via an eHMI with their surrounding traffic environment ensuring a safe and accepted interaction among all traffic participants (TPs), e.g., pedestrians. Therefore, their messages should be universally understood. The question that arises is how TPs’ information needs may differ for different vehicle types, how this needs to be considered in the eHMI design and if different TP age groups, especially elderly, need other information for a safe and accepted interaction. However, little research addressing this question was done so far. Results of our current experimental online study (N = 321) in a shared space setting revealed that especially explicit communication via an eHMI is beneficial for interaction. Furthermore, results indicated an overall good implementation of the explicit eHMI communication strategies. Pedestrians felt safer, better informed, and indicated a more positive affective valence in interaction with HAVs with dynamic eHMI vs. static eHMI vs. no eHMI. In terms of a universal design, this was true for all age groups. As vehicle type had a significant effect on the pedestrians’ feelings of safety and their perceived affective valence in interaction, eHMI might have an especially beneficial effect when interacting as a pedestrian with a large vehicle.