Automation transparency: Designing an external HMI for autonomous passenger ferries in urban waterways

Automation transparency - the visibility of responsibilities, capabilities, goals, activities, and effects of autonomous systems - is not only important for the operator, but also relevant for other humans in the system's environment. This pictorial investigates current trends in the development of External Human-Machine Interfaces (eHMIs) and highlights the most important factors for designing eHMIs. Further, it explores automation transparency for a self-driving passenger ferry for urban waterborne transport and how it can communicate messages about the system's perceptions, current state and future intention to nearby ships and bystanders through an eHMI. As a result of a user-centred design process, we propose a unique eHMI design making an urban autonomous passenger ferry capable of expressing its state and intention to nearby ships and humans via displays, light, and moving panels. The results of this paper can inform designers of the importance of automation transparency for autonomous waterborne transport systems.