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

Christina Kaß,Alexandra Neukum,Frederik Naujoks,Stefanie Schoch,Andreas Keinath,Sebastian Hergeth

doi:10.3390/info11030173

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.

Highlights

With the introduction of automated vehicles into mixed traffic environments, drivers may be allowed to engage in non-driving-related tasks while driving
We have proposed a methodological framework that consists of a method to deduce relevant use cases, a definition of specific usability requirements and appropriate parameters, and a test protocol for the empirical evaluation of an external human–machine interfaces (eHMIs)
The proposed multi-stage gradual methodological approach presented in this article claims to consider all theoretically possible use cases of an eHMI

Summary

Introduction

With the introduction of automated vehicles into mixed traffic environments, drivers may be (temporarily) allowed to engage in non-driving-related tasks while driving. The drivers of automated vehicles will often be unavailable for communication while their vehicle is interacting with non-automated road users. EHMI systems represent a completely new and immature technology. Before introducing such a new technological system to the market and to the traffic environment, it is important to carefully determine its usability. Studied eHMI approaches basically differed with regard to the content of communication (e.g., maneuver intention, automation status, and request for action) [3] and concrete interface design solutions (e.g., the position and modality of the signal) [4,5,6,7,8].

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