How Can Autonomous Vehicles Convey Emotions to Pedestrians? A Review of Emotionally Expressive Non-Humanoid Robots
Yiyuan Wang, Luke Hespanhol, Martin Tomitsch
TL;DR
This review investigates how autonomous vehicles can convey emotions to pedestrians through non-humanoid, affective interfaces. By systematically analyzing 25 studies (2011–2021) on emotionally expressive non-humanoid robots, it delineates emotion models (categorical, dimensional, personas), output modalities (visual, auditory, haptic), evaluation approaches, and user perceptions. The authors synthesize five design considerations for emotional expressions in AVs and six broader considerations for affective AV-pedestrian interfaces, aiming to guide the development of socially intelligible, context-aware eHMIs. The findings suggest that multi-modal, intuitive emotion encoding aligned with AV function and pedestrian expectations can improve acceptance and safety, while context and culture modulate interpretation. The work provides a foundation for integrating affective dimensions into AV-pedestrian communication and outlines avenues for future empirical research and design exploration.
Abstract
In recent years, researchers and manufacturers have started to investigate ways to enable autonomous vehicles (AVs) to interact with nearby pedestrians in compensation for the absence of human drivers. The majority of these efforts focuses on external human-machine interfaces (eHMIs), using different modalities, such as light patterns or on-road projections, to communicate the AV's intent and awareness. In this paper, we investigate the potential role of affective interfaces to convey emotions via eHMIs. To date, little is known about the role that affective interfaces can play in supporting AV-pedestrian interaction. However, emotions have been employed in many smaller social robots, from domestic companions to outdoor aerial robots in the form of drones. To develop a foundation for affective AV-pedestrian interfaces, we reviewed the emotional expressions of non-humanoid robots in 25 articles published between 2011 and 2021. Based on findings from the review, we present a set of considerations for designing affective AV-pedestrian interfaces and highlight avenues for investigating these opportunities in future studies.