Standardized Test Procedure for External Human–Machine Interfaces of Automated Vehicles

Abstract

Research on external human–machine interfaces (eHMIs) has recently become a major area of interest in the field of human factors research on automated driving. The broad variety of methodological approaches renders the current state of research inconclusive and comparisons between interface designs impossible. To date, there are no standardized test procedures to evaluate and compare different design variants of eHMIs with each other and with interactions without eHMIs. This article presents a standardized test procedure that enables the effective usability evaluation of eHMI design solutions. First, the test procedure provides a methodological approach to deduce relevant use cases for the evaluation of an eHMI. In addition, we define specific usability requirements that must be fulfilled by an eHMI to be effective, efficient, and satisfying. To prove whether an eHMI meets the defined requirements, we have developed a test protocol for the empirical evaluation of an eHMI with a participant study. The article elucidates underlying considerations and details of the test protocol that serves as framework to measure the behavior and subjective evaluations of non-automated road users when interacting with automated vehicles in an experimental setting. The standardized test procedure provides a useful framework for researchers and practitioners.

A Systematic Review of Virtual Reality Applications for Automated Driving: 2009–2020

“…However, such eHMIs are not limited to visualization only (e.g., Chang et al, 2017;Stadler et al, 2019), indeed, they can be used for interaction purposes, such as active route navigation for pedestrians using gesture interaction (Gruenefeld et al, 2019). We encourage researchers to investigate eHMIs not only for pedestrians, but also for cyclists to enable safe interactions, and foster social connections between automated vehicles and vulnerable road users, for example by defining a common understanding, or guidelines, between them Kaß et al (2020). Additionally, our review shows that most eHMI research is focused on SAE L5 fully automated vehicles, however, conditionally automated vehicles need to communicate with pedestrians as well, as the driver might not be fully attentive to the road environment, yet still being present in the vehicle.…”

External Human-Machine Interfaces: Which of 729 Colors Is Best for Signaling ‘Please (Do not) Cross’?

“…A limitation of our research is that we used static stimuli. We have further disregarded factors such as eHMI visibility and attention-grabbing in environments where traffic may approach from multiple directions (e.g., [52]) or environments with visual distractions (see [53], for a recommended standardized test procedure for eHMIs). In addition, we have not investigated the extent to which different colors contribute to glare, nor have we investigated whether certain colors can be confused with each other in different environmental conditions, such as during the day versus at night (see, for example, [54], [55]).…”

Editorial for Special Issue: Test and Evaluation Methods for Human-Machine Interfaces of Automated Vehicles

“…Their potential benefits and drawbacks are discussed in the technical and scientific community, but there are currently no available standards for their implementation. Therefore the first paper "Standardized Test Procedure for External Human-Machine Interfaces of Automated Vehicles", by Kaß, Schoch, Naujoks, Hergeth, Keinath and Neukum [5] presents a standardized test procedure that enables the effective usability evaluation of eHMIs from the perspective of multiple road users. The paper includes a methodological approach to deduce relevant use cases as well as specific usability requirements that should be fulfilled by an eHMI to be effective, efficient, and satisfying.…”