In a vehicle traffic system, the predetermined nominal trajectory for an autonomous vehicle is varied periodically within acceptable boundaries which define a permitted travel corridor. The corridor's boundaries ensure the continued safe and controlled operation of the vehicle within the system. In an embodiment of the invention, alternative trajectories are selected randomly; in another, they are parallel to one another. In yet another, preferred embodiment, judiciously-selected, alternative trajectories are repeated periodically according to a predetermined schedule designed to avoid repetitive travel over the same precise path, and possibly also selected for optimal results under different terrain, environmental, and/or operational conditions. According to another aspect of the invention, the shape and size of the corridor defining the boundaries for safe operation are varied in response to changed conditions to increase operational flexibility. Thus, by avoiding repeated passage precisely over the path of the nominal trajectory, rutting on the road is greatly reduced and a more uniform surface is maintained for travel.