The five year development of NAVMATE from 1989 through its deployment as GUIDESTAR in the 1995 Oldsmobile 88 is discussed within the context of three development phases of hardware and software. In Phase I, fundamental issues of the turn-by-turn route guidance concept and the factors affecting vehicle positioning were assessed. In Phase II, prototype hardware that utilized the CRT display and touch screen of the 1992 Trofeo were built to test customer response. The aftermarket installation design of Phase III (current design) focussed on a simplified man-machine interface, ease of system installation and removal and robust performance. This design provided the basis for the Oldsmobile GUIDESTAR System.