| Abstract |
Automated vehicles (AVs) are rapidly transforming smart cities, offering potential benefits such as improved safety, performance, mobility, accessibility, and overall user experience in traffic. A key area of focus in this evolution is the development of external human-machine interfaces (eHMIs) which aim to equip AVs with communication capabilities. Said interfaces address critical challenges, including mitigating safety risks and enhancing traffic flow in scenarios where drivers are inattentive or altogether absent, and play an important role in allaying distrust of the general public in AVs. Considering the research field of eHMIs is relatively young, it is unsurprising that standardized eHMI evaluation procedures are yet to be established. As a result, the effectiveness and efficiency of eHMI concepts are often assessed either simultaneously within the same evaluation procedure or separately but in otherwise similar procedures. Unfortunately, these approaches overlook on the whole the fundamental differences between the two constructs, resulting in limitations relating to the validity, reliability, and comparability of the findings. Here, I present a definitive framework aimed at disentangling efficiency from effectiveness by guiding methodological choices regarding design rationale explanation, instructions emphasizing speed, trial-level time limit, and targeted performance measures, depending on the research questions of interest. Copyright © 2025 by SCITEPRESS - Science and Technology Publications, Lda. |
