CARGuide: on-board computer for automobile route guidance

This paper describes the Computer for Automobile Route Guidance (CARGuide), a prototype system designed and built at Carnegie-Mellon University. CARGuide is a portable, microcomputer-based system to aid drivers in route finding and navigation in city streets. Given starting and destination intersections, CARGuide calculates an optimum route to the destination, displays portions of the street map containing the route, and highlights the streets on the route by flashing them on a display. It provides automatic or manual zooming into the map picture and speaks driving directions along the route. Both hardware and software design is explained in the paper. The hardware consists of a 68000 processor on a Multibus, bubble memories for secondary storage, a 128 x 128 dot matrix fluorescent display, a speech synthesizer, RAM, control and interface logic for the components, and a keyboard. A total of six circuit boards are used, four of them designed at CMU. A compact street map database is constructed from a regular street map and is stored in CARGuide's half megabyte secondary storage. An efficient optimum route-finding scheme was implemented, which uses a divide and conquer method and precomputed routes to improve the performance of a shortest-path algorithm. For optimum route calculations, streets are given weights estimating the travel time, and penalties are introduced for turns and crossing intersections. CARGuide has been tested by implementing a portion of the Pittsburgh street map.