The rear wheels steer in conjunction with variables such as front wheel steering angle and vehicle speed. They only steer a limited angle, but at low speeds, the rear wheels steer in the opposite direction as the front wheels to lessen the turning radiius of the car and is handy for u-turns and parking.
At high speeds in excess of 70kmh, the rear wheels then turn towards the same angle as the front wheels to aid in overtaking. From personal experience, I also feel that 4ws allows you to take a wider turn-in angle since the rear wheels allow the current line to be 'tightened' throughout a turn... takes some getting used to though.
Bookmarks