Pedestrian Information Needs for eHMI Design Across Visibility Conditions: A Gap Analysis of ISO/PAS 23735

As automated vehicles remove the interpersonal cues pedestrians rely on when crossing, external human-machine interfaces (eHMIs) have been proposed as an alternative means of communication. ISO/PAS 23735:2025 defines seven information types for eHMI design, yet whether these categories fully cover pedestrian needs across varying visibility conditions remains unclear. In a within-subjects study, 30 pedestrians described their information needs across four crossing scenarios spanning full to zero vehicle visibility. Under good visibility, intent dominated and ISO/PAS 23735 coverage reached 96.6% to 100.0%. Under complete occlusion, coverage dropped to 26.7%; two absent categories account for the gap: presence (vehicle existence and approach confirmation), required by 93.3% of participants, and spatial information (real-time position, direction, distance, and time-to-contact), required by 30.0%. Pedestrian information needs shift qualitatively with visibility, and low-visibility conditions introduce requirements beyond the framework’s intended scope. A Visibility-Adaptive Information Framework is proposed to address this shift.