This paper describes development and performance verification of a driving control algorithm for a 6 wheel driving and 6 wheel steering (6WD/6WS) vehicle using a real-time simulator. This control algorithm is developed to improve vehicle stability and maneuverability under high speed driving conditions. The driving controller consists of stability decision, upper, lower level and wheel slip controller. The stability decision algorithm determines desired longitudinal acceleration and reference yaw rate in order to maintain lateral and roll stability using G-vectoring method. Upper level controller is designed to obtain reference longitudinal net force, yaw moment and front/middle steering angles. The longitudinal net force is calculated to satisfy the reference longitudinal acceleration by the PID control theory. The reference yaw moment is determined to satisfy the reference yaw rate using sliding control theory. Lower level controller determines distributed tractive/braking torques. The lower level controller is based on optimal distribution control and designed using the friction circle which means maximum generated tire force on each wheel. Distributed longitudinal tire forces are in proportion to the friction circle. The wheel slip controller is designed to keep the slip ratio of each wheel below the maximum slip ratio. The response of the 6WD/6WS vehicle with the driving controller has been evaluated via computer simulations using TruckSim dynamic model and a real-time simulator. Frequency analysis of linearized control system, vehicle-driver-controller closed loop and fish hook maneuver open-loop simulations have been conducted to investigate the improved performance of the proposed optimal coordination controller.