  Automotive user interfaces constantly change due to increasing automation,
novel features, additional applications, and user demands. While in-vehicle
interaction can utilize numerous promising modalities, no existing overview
includes an extensive set of human sensors and actuators and interaction
locations throughout the vehicle interior. We conducted a systematic literature
review of 327 publications leading to a design space for in-vehicle interaction
that outlines existing and lack of work regarding input and output modalities,
locations, and multimodal interaction. To investigate user acceptance of
possible modalities and locations inferred from existing work and gaps unveiled
in our design space, we conducted an online study (N=48). The study revealed
users' general acceptance of novel modalities (e.g., brain or thermal activity)
and interaction with locations other than the front (e.g., seat or table). Our
work helps practitioners evaluate key design decisions, exploit trends, and
explore new areas in the domain of in-vehicle interaction.
