Electronic Route Guidance System

Electronic Route Guidance System (ERGS) was a 1970s era government sponsored in-vehicle navigation and route guidance system used in the United States. ERGS was the initial stage of a larger research and development effort called the Intelligent Transportation System (ITS). Other programs include Japan's CACS and similar projects in Europe.
ERGS was a destination oriented system that required a human driver to enter a destination code into the vehicle system. The vehicle communicated with an instrument intersection where the destination code was decoded and routing information was sent back to the vehicle.
Links.
http://www.wirelesscommunication.nl/reference/chaptr01/roadtrin/ivhsrout.htm