Communications systems will be used to disseminate information needed for coordination and control of automated vehicle highway systems. Four types of communications functions are defined, including navigation and route guidance, highway system traffic management, manoeuvre coordination, and headway maintenance. The vehicle-to-vehicle communications implemented for the platoon scenario in the AHS 1997 Demonstration of Technical Feasibility is used to present an example of current AHS applications. The ability of existing wireless communications technologies to meet future AHS communications requirements is discussed.