Towards Inclusive External Human-Machine Interface: Exploring the Effects of Visual and Auditory eHMI for Deaf and Hard-of-Hearing People
This study addresses the lack of inclusive design in external human-machine interfaces (eHMIs) for autonomous vehicles, which commonly overlook the communication needs of deaf and hard-of-hearing (DHH) individuals. It presents the first systematic investigation into eHMI usability for DHH users, employing focus group interviews, virtual reality simulations, eye-tracking, and subjective evaluations to compare visual and auditory eHMI modalities. Findings reveal that visual eHMIs significantly reduce crossing decision time and gaze duration for DHH participants while enhancing their trust, perceived safety, and perceived system usefulness, whereas auditory eHMIs yield limited effectiveness. Building on these insights, the study proposes five inclusive eHMI design principles tailored to DHH users, thereby addressing a critical gap in accessible intelligent transportation interaction research.