Longitudinal Effects of External Communication of Automated Vehicles in the USA and Germany: A Comparative Study in Virtual Reality and Via a Browser

Automated vehicles are expected to communicate with vulnerable road users. In two longitudinal studies, we investigated the impact of external Human-Machine Interfaces (eHMI) on pedestrian safety and behavior when interacting with automated vehicles. Utilizing LED strips for communication, these studies probed various factors, including mixed traffic scenarios, presence of eHMIs, and being from Germany or the USA. Our experimental approaches included a Virtual Reality study with 24 participants in Germany and an online study with 28 participants from the USA and Germany. Results revealed that repeated interactions with automated vehicles featuring eHMI significantly enhance pedestrian Trust, Understanding, and perceived safety, while simultaneously diminishing mental workload. Notably, the positive effects of eHMI were consistent across the two countries. US participants exhibited a tendency for higher risk-taking in crossing situations and reported lower mental workloads, underscoring the importance of considering cultural nuances in designing eHMI systems for mixed-traffic environments.