Design of External Human-Machine Interfaces for Different Vehicle Types

Abstract

Future traffic will be determined by the joint interaction of highly automated vehicles (AV) and other traffic participants, e.g., pedestrians, in mixed traffic environments. To ensure a safe and efficient traffic flow, AVs must be able to communicate with the traffic environment. An external human-machine interface (eHMI) seems to be a promising solution to transmit explicit information to other traffic participants and to enable an adequate communication. However, it remains unclear how information needs differ for different vehicle types and how this must be considered in the eHMI design. Therefore, this experimental online study investigates information needs when interacting with two different AV types (car vs. bus) both equipped with the same eHMI communication strategies (mode awareness, intention-based, perception-based, combination) based on a LED light-band as eHMI. Video sequences were shown in which the participants crossed a shared space from a pedestrian’s perspective in front of both vehicle types equipped with the eHMI communication strategies. Results showed that participants felt significantly safer for both vehicle types (car and bus) for all three eHMI explicit communication strategies (intention-based, perception-based, combination) vs. mere mode awareness or no eHMI at all. Comparing both vehicle types (car vs. bus), descriptive statistics indicated that participants felt safer and more comfortable when interacting with a car compared to a bus. This effect was significant for the perceived comfort showing that participants felt more comfortable when interacting with a car compared to a bus both equipped with an eHMI communication strategy combining intention-based and perception-based eHMI.