Effects of Auditory Information for People With Visual Impairments in Highly Automated Vehicles

As automated vehicles (AVs) become more prevalent, their design often prioritizes visual interfaces, which creates significant accessibility barriers for blind and visually impaired (BVI) users. This study investigates the optimal amount of auditory information required to keep BVI passengers informed and trusting of an AV without overwhelming them. The researchers sought to determine the impact of varying levels of auditory detail on cognitive load, situation awareness, trust, and user experience.

The researchers conducted an online video-based study with 35 participants, including 12 BVI individuals. Participants watched videos of a simulated AV journey through urban, rural, and highway environments. The study compared three levels of auditory information:

• Low: Safety-relevant information only (e.g., start/stop, warnings).
• Medium: Safety-relevant information plus vehicle control and route updates.
• High: Medium information plus sightseeing and destination-specific environmental details.

The auditory design utilized a combination of non-speech sounds (earcons) and synthesized speech to convey information, ensuring that the interface remained accessible without requiring specialized hardware.

The study found that moving from low to medium information significantly improved trust, understanding, and overall user experience for both sighted and BVI participants. However, the transition from medium to high information did not yield further benefits and instead suggested that users reached a point of information saturation. While perceived safety also improved with more information, the effect was less robust than the improvements in trust and user experience. The results suggest that while BVI passengers desire more information than just basic safety alerts, there is a clear threshold where additional context becomes redundant or potentially distracting.