A road vehicle utilizes hydraulic machines for primary and accessory vehicle drive functions. An internal combustion engine directly drives a first variable capacity hydraulic machine selectively operable as pump or motor, an electric machine electrically coupled to a storage battery is selectively operable as motor or generator and is mechanically coupled to a second hydraulic machine operable as pump or motor, and at least one hydraulic drive motor is coupled to a vehicle drive wheel. A controller regulates the capacity of the first hydraulic machine, and controls the functionality of the first and second hydraulic machines to selectively crank the engine or charge the storage battery. The first hydraulic machine also supplies hydraulic fluid to accessory drive motors including a power steering drive motor, an air compressor drive motor and a supercharger drive motor.