Designing multi-modal communication for merge negotiation with automated vehicles: Insights from a design exploration with prototypes

Gao, R., Liu, H., Bazilinskyy, P., Martens, M. H.

Adjunct Proceedings of the 17th International Conference on Automotive User Interfaces and Interactive Vehicular Applications (AutoUI). Brisbane, QLD, Australia (2025)

ABSTRACT Deciding whether to allow an automated vehicle (AV) to merge in front can present a complex negotiation for human drivers. To address this, we explored the human-machine interface (HMI) design for merge negotiation between a manually driven vehicle and an AV from the human driver's perspective. We developed five HMI designs, each integrating different combinations of visual cues, haptic alerts, and explicit approve and reject controls. They were evaluated together with two baseline conditions in a video-based driving simulator. The results of Likert-scale ratings indicated that HMI designs with explicit accept and reject controls received higher mean ratings in communication clarity, perceived adequacy, safety perception, trust in AV behaviour, and decision-making efficiency than those without such controls. Open-ended feedback further suggested that these HMIs may foster a stronger sense of control and reduce perceptions of aggressiveness. Based on the findings, we outlined three preliminary design considerations for HMIs that support merge negotiation between AVs and human drivers. This work offers early guidance and sets the stage for future research on integrating diverse modalities and driver inputs (e.g., explicit approve and reject controls) into HMI design for merge negotiation.