Highly automated vehicles' implicitly and explicitly communicated intents to interact with pedestrians and pedestrians' appraisals across different cultures

Abstract

Research has shown that highly automated vehicles (HAVs) pose new challenges for safe interactions with pedestrians in mixed-traffic scenarios, particularly regarding how vehicle intent is communicated. Such intent can be signaled implicitly by vehicle kinematics and/or explicitly by using external human-machine interfaces (eHMIs) such as light-bands on the vehicle's exterior. However, studies providing deeper understanding of the interplay of implicit and explicit signals for HAVs' communications with interacting pedestrians and especially comparable across different cultures are missing. But that is exactly what is missing essential for developing a universal design and standardized guidelines here. To bridge this gap, our experimental online study replicated previous experiments from Germany, Japan, and Singapore now with Dutch and British samples to examine the generalizability of eHMI effects across cultures. Participants were presented with HAVs varying in explicit (intention-based eHMI, static eHMI, none) and implicit communication style (yielding, non-yielding). We assessed pedestrians' willingness to cross (WTC), perceived safety, and perceived trustworthiness and support of the eHMI. Results across all five samples revealed similar patterns: intention-based light-bands significantly increased WTC and perceived safety compared to static or absent eHMIs, and were rated as more trustworthy and supportive. However, when explicit and implicit signals contradicted each other, participants showed potentially dangerous overreliance on the explicit signal. The national samples differed slightly in the extent of this overreliance. These findings emphasize both promises and risks of light-band eHMIs and underscore the need for universal, standardized design guidelines that mitigate overreliance while enhancing pedestrian safety in mixed-traffic environments.