Extensive analytical work was undertaken on using the active steering system EPS (Electric Power System) for automatic driving of a motor vehicle (a two-axle motor truck of medium load capacity, provided with typical ESC - Electronic Stability Control system components as well as obstacle detectors and road monitoring systems) in the situation when an obstacle has suddenly sprung up. This paper presents a fragment of this work, which includes results of simulation investigation of dynamics of the lane-change process in an “open” and “closed-loop” system, i.e. with the automatic control function of the active steering system (EPS) being used in the latter case. The theoretical deliberations and simulation tests were based on mathematical models of the controlled system and the controller. The model of the controlled system includes a complex and detailed representation of the dynamics of motion of a motor truck, where the non-linearities and three-dimensionality of the vehicle motion are taken into account. The controller model is based on a reference model, which is considerably simplified and, in consequence, very effective in the carrying out of the necessary real-time calculations. The automatic controller operates like a Kalman regulator in a closed-loop system.