Automatic vehicle following is an important feature of a fully or partially automated highway system (AHS). The on-board vehicle control system should be able to accept and process inputs from the driver, the infrastructure, and other vehicles, perform diagnostics, and provide the appropriate commands to actuators so that the resulting motion of the vehicle is safe and compatible with the AHS objectives. The purpose of this article is to design and test a vehicle control system in order to achieve full vehicle automation in the longitudinal direction for several modes of operation, where the infrastructure manages the vehicle following. These modes include autonomous vehicles, cooperative vehicle following, and platooning. The vehicle control system consists of a supervisory controller that processes the inputs from the driver, the infrastructure, other vehicles, and the on-board sensors and sends the appropriate commands to the brake and throttle controllers. In addition, the controller makes decisions about normal, emergency, and transition operations. Simulation results of some of the basic vehicle following maneuvers are used to verify the claimed performance of the designed controllers. Experiments on Interstate-15 that demonstrate the performance of the throttle controller with and without vehicle-to-vehicle communications in an actual highway environment are also included.