BMW has that on many models, rear wheel steering and variable-ratio at the front. It's an option they call Integral Active Steering. The rear is steered either

BMW has that on many models, rear wheel steering and variable-ratio at the front. It's an option they call Integral Active Steering. The rear is steered either against or with the front, so it will make a tighter turn on a parking lot and it will "crab" on the highway for extra comfort when changing lanes. The front ratio uses a planetary gear set to give you a higher or lower steering-ratio based on speed, and it allows the stability control to automatically counter-steer a bit when loosing traction at the rear.