In this chapter the design of active steering assistance systems for heavy vehicles is discussed. These kinds of systems are oriented to avoid the rollover and prevent lane departure of the vehicle. The methodology herein illustrated is based on the super-twisting algorithm. An estimator relying on high order sliding mode observer is developed in order to get information on the vehicle dynamics, such as lateral acceleration limit and the height of the center of gravity. The lateral position and lateral speed are controlled using sliding mode control in order to ensure the stability of the vehicle and avoid accidents. While in standard practical situations the lateral offset and the relative yaw angle are typically measured and the road curvature can be assumed known, the identification of some relevant parameters of the model needs to be carried out in order to increase the robustness of the control system, as discussed in the chapter. Simulation and experimental results are reported, making reference to a tractor model, in order to show the quality of the presented concept.