Uncertainty on Display: The Effects of Communicating Confidence Cues in Autonomous Vehicle-Pedestrian Interactions

TL;DR

This study explores how autonomous vehicles can communicate their decision-making uncertainty to pedestrians using explicit displays and implicit cues, finding that explicit communication improves safety, trust, and user experience.

Contribution

It provides empirical evidence on effective methods for conveying AV uncertainty, highlighting the superiority of explicit confidence displays over implicit cues.

Findings

Explicit communication improves perceived safety and trust.

Implicit cues can cause ambiguity, especially at low confidence levels.

Participants preferred explicit confidence displays for understanding AV intentions.

Abstract

Uncertainty is an inherent aspect of autonomous vehicle (AV) decision-making, yet it is rarely communicated to pedestrians, which hinders transparency. This study investigates how AV uncertainty can be conveyed through two approaches: explicit communication (confidence percentage displays) and implicit communication (vehicle motion cues), across different confidence levels (high and low). Through a within-subject VR experiment (N=26), we evaluated these approaches in a crossing scenario, assessing interface qualities (visibility and intuitiveness), how well the information conveyed the vehicle's level of confidence, and their impact on participants' perceived safety, trust, and user experience. Our results show that explicit communication is more effective and preferred for conveying uncertainty, enhancing safety, trust, and user experience. Conversely, implicit communication introduces ambiguity, especially when AV confidence is low. This research provides empirical insights into how uncertainty communication shapes pedestrian interpretation of AV behaviour and offer design guidance for external interfaces that integrate uncertainty as a communicative element.