Towards Inclusive External Human-Machine Interface: Exploring the Effects of Visual and Auditory eHMI for Deaf and Hard-of-Hearing People

TL;DR

This study explores how visual and auditory external human-machine interfaces (eHMIs) affect Deaf and Hard-of-Hearing individuals' interaction with autonomous vehicles, aiming to improve inclusivity and safety.

Contribution

It provides empirical evidence on the effects of visual and auditory eHMIs on DHH people's perceptions and behaviors, and offers practical design recommendations for inclusive eHMI development.

Findings

Visual eHMIs reduce time to cross the road and gaze duration.

Both visual and auditory eHMIs increase trust and perceived safety.

DHH participants focus more on AVs during interactions.

Abstract

External Human-Machine Interfaces (eHMIs) have been proposed to facilitate communication between Automated Vehicles (AVs) and pedestrians. However, no attention was given to Deaf and Hard-of-Hearing (DHH) people. We conducted a formative study through focus groups with 6 DHH people and 6 key stakeholders (including researchers, assistive technologists, and automotive interface designers) to compare proposed eHMIs and extract key design requirements. Subsequently, we investigated the effects of visual and auditory eHMI in a virtual reality user study with 32 participants (16 DHH). Results from our scenario suggesting that (1) DHH participants spent more time looking at the AV; (2) both visual and auditory eHMIs enhanced trust, usefulness, and perceived safety; and (3) only visual eHMIs reduced the time to step into the road, time looking at the AV, gaze time, and percentage looking at active visual eHMI components. Lastly, we provided five practical implications for making eHMI inclusive of DHH people.