A steering system comprises a steering wheel adapted to receive a driver's rotational input. Left and right wheel units are rotatable along a steering angle for adjusting a direction of the vehicle during the driving movement. A steering mechanism converts the rotational input to a variation of the steering angle of the wheel units. The steering mechanism comprises a steering shaft connected to the steering wheel, and gear steering units for each said wheel unit. The gear steering units are connected to the steering shaft for mechanically converting the rotational input to steering outputs for both said wheel units to concurrently vary the steering angle of said wheel units. Independent steering units for each wheel unit each adjusting the steering angle of a respective one of the wheel units independently from the rotational input and from the other wheel unit.