The aim of the research is to study the planeparallel movement in a horizontal plane of a wide-span gantry tractor equipped with a skid-steering system. The theoretical studies are based on the foundations of the tractor theory and theoretical mechanics. As a results, it was found that the implementation of the skid-steering system on the gantry tractor leads to a significant change in its yawing angle by an average of 1 degree per 0.1 s and its insignificant lateral displacement. Rotations as well as transversal displacements of the longitudinal axis of the gantry vehicle from a pre-set trajectory require successive and consecutive rotations in the opposite directions to realign the machine to the tracks of the permanent traffic lanes. Experimental tests were performed using the skid-steer gantry tractor developed by the authors to evaluate the oscillations of the yawing angle and transverse displacements throughout the motion of the machine along the tracks of the permanent traffic lanes. The fluctuations were in the frequency range from 0 to 2 s –1 for both parameters.