  Human-Machine Interfaces (HMIs) for automated vehicles (AVs) are typically
divided into two categories: internal HMIs for interactions within the vehicle,
and external HMIs for communication with other road users. In this work, we
examine the prospects of bridging these two seemingly distinct domains. Through
a participatory workshop with automotive user interface researchers and
practitioners, we facilitated a critical exploration of holistic HMI design by
having workshop participants collaboratively develop interaction scenarios
involving AVs, in-vehicle users, and external road users. The discussion offers
insights into the escalation of interface elements as an HMI design strategy,
the direct interactions between different users, and an expanded understanding
of holistic HMI design. This work reflects a collaborative effort to understand
the practical aspects of this holistic design approach, offering new
perspectives and encouraging further investigation into this underexplored
aspect of automotive user interfaces.
