Evaluation of External HMIs for Automated Shuttles Based on a Real-World Platform

This study examines Human-Machine Interface (HMI) systems for automated shuttles, focusing on communication with cyclists. Using a Virtual Reality (VR) simulation based on a real automated shuttle platform within the Ride the Future project, four HMI systems were tested: purple light projections, emotional eyes, auditory alerts, and informative text. These systems aimed to enhance safety and trust by signalling the shuttle’s intentions. The study involved 28 participants, including both individuals familiar with the shuttles’ existing communication methods and those encountering them for the first time. Findings indicate that auditory alerts and text-based HMIs were the most effective, being clear and easily understood. In contrast, the purple light was difficult to see in daylight, and the emotional eyes were often misinterpreted. Principal Component Analysis (PCA) identified three key factors: predictability, endangerment, and practicality, underscoring the need for intuitive and simple designs over purely innovative solutions. Participants stressed that clarity and familiarity are crucial for HMI effectiveness. By using simulation while maintaining a foundation in real-world shuttle technology, this study provides controlled yet applicable insights into HMI usability. The findings highlight the potential of HMIs to support automated shuttle integration into public transport by improving road safety and user experience. Future research should assess the long-term impact of these systems in real-world traffic conditions. The motivation for the present study arises from this limitation, aiming to contribute to the field by empirically examining how eHMI functions in an authentic urban traffic environment.