In a first forward drive mode, at speeds of the vehicle lower than a predetermined speed, an
electric traction motor (17) drives the wheels (12, 13) of the vehicle, while an internal-
combustion engine (27) drives an
electric generator (34) or rests. The generator charges an electric battery (38), or powers the
traction motor, or both. In a second forward drive mode, at speeds of the vehicle higher than the predetermined speed, the engine drives the
electric generator and the wheels of the vehicle, while the
traction motor is not energized. In a third forward drive mode, at speeds of the vehicle higher than the predetermined speed, the
traction motor, powered by the electric battery, together with the engine drive the wheels of the vehicle. In a reverse drive mode the traction motor alone drives the wheels of the vehicle. A
clutch (32) selectively interrupts the
power transmission between the engine and the wheels of the vehicle. The traction motor selectively operates as an electric braking generator, during speed retardation and braking of the vehicle, and charges the electric battery. A central
electronic controller (46) controls and coordinates the operation of the
clutch, traction motor, and engine for achieving high
fuel efficiency at both city and highway operational conditions.