Automation of vehicles not only provides greater safety, but also many previously unimagined opportunities, such as less inequality, less stress, and more meaningful activities while driving. However, the uptake and implementation of automated driving have been falling short of its promise, due to challenges in identifying safe and acceptable ways for humans to interact with automated vehicles. The human-machine interface (HMI) in vehicles plays a more critical role today than ever before. The main research question addrssed in this study, as part of the EU-funded HADRIAN project, is: What steps need to be taken to achieve effective fluid HMI (f-HMI) design for improved driver-vehicle dialogue, especially in critical scenarios?.