eHMI for All -- Investigating the Effect of External Communication of Automated Vehicles on Pedestrians, Manual Drivers, and Cyclists in Virtual Reality

Colley, Mark; Kopp, Simon; Dey, Debargha; Jansen, Pascal; Rukzio, Enrico · 2026 · arXiv

DOI: 10.1145/3772318.3790585

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Summary

This study addresses the lack of comparative research on how External Human-Machine Interfaces (eHMIs) affect different road users—specifically pedestrians, manual drivers, and cyclists. While prior work has largely focused on pedestrian-automated vehicle (AV) interactions, it remains unclear whether a unified eHMI design can effectively communicate AV intentions across all three roles without causing information overload or requiring multiple distinct interfaces. The authors investigate whether a single eHMI concept can facilitate safe and intuitive interactions for diverse road users under varying levels of environmental distraction. To answer this, the researchers conducted a within-subjects virtual reality experiment with 40 participants. Each participant experienced all three road user roles using specialized simulators: a free-walking space for pedestrians, a steering wheel and pedal setup for drivers, and a stationary bicycle with a wind machine for cyclists. The study employed a Slow-Pulsing Light Band (SPLB) eHMI, which blinked to indicate the AV’s intention to yield. The experimental design included three distraction conditions: no distraction, visual noise (non-interacting bystanders), and interference (conflicting trajectories from other road users). Participants completed 18 scenarios in total, with their behavior, gaze, and subjective perceptions measured via eye-tracking and questionnaires, including the NASA-TLX for mental demand and custom scales for trust, safety, and usability. The results demonstrated that the eHMI had positive effects across all three road user roles. Participants reported higher safety perceptions, increased trust in the AV, greater perceived usefulness, and lower mental demand when the eHMI was present compared to when it was absent. While road user role and distraction level showed significant main effects on these metrics, interaction effects were limited to perceived usability. This indicates that the eHMI’s impact on core safety and trust metrics was consistent regardless of whether the user was walking, driving, or cycling, or whether they faced visual noise or interference. The significance of these findings lies in the support for a holistic approach to eHMI design. The study suggests that a unified eHMI concept is effective for diverse road users, potentially simplifying the standardization and broader adoption of AV communication systems. By demonstrating that a single interface can adequately serve pedestrians, drivers, and cyclists, the research argues against the need for multiple, role-specific eHMIs, which could lead to cluttered interfaces and information overload. This contributes to the field by providing evidence for scalable, inclusive eHMI designs that enhance traffic safety and predictability in complex, multi-agent environments.

Key finding

A unified external Human-Machine Interface design effectively improved safety perceptions, trust, and perceived usefulness while reducing mental demand for pedestrians, manual drivers, and cyclists in virtual reality scenarios.

Methodology

simulator

Sample size: 40

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archive success canonical_url 1 2026-06-06
extract success cached 3 2026-06-10
clean success clean 1 2026-06-04
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enrich success openalex 2 2026-05-08
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summarize success llm qwen3.6-27b-prismaquant summ-v5 2 2026-06-10
tag success vector_similarity 15 2026-06-11
verify partial 2 2026-06-10

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