The introduction of steer-by-wire system technology into ground transportation vehicles permits customization of the human-machine haptic interface to accommodate the driver's desired level of road ldquofeel.rdquo The ability to tune the steering system's dynamic behavior can potentially enhance the driver's overall performance and increase the vehicle's safety. A nonlinear tracking controller is designed to ensure that the directional control steering assembly follows the operator's commanded maneuvers at the driver interface. In addition, the controller provides the driver with tunable force feedback proportional to the reaction forces at the tire-road interface. Two control techniques are provided to guarantee that the corresponding tracking errors are asymptotically forced to zero. The first compensates for parametric uncertainty, whereas the second eliminates the need for torque measurements through the use of observers. Representative numerical and experimental results are presented to demonstrate the controller's performance for various driving scenarios.