We present an initial set of design principles for designing efficient, effective, coherent, and desirable adaptive spoken interaction for traffic information and navigation. The principles are based on a qualitative analysis of driver interactions with an adaptive speech prototype along with driver interviews. The derived set of principles range from high-level fundamental design values, conceptual and behavioral principles, to low-level interface-level principles that can guide the design of adaptive spoken dialogue interaction in the car from a user experience perspective. © 2014 ACM.