Abstract: This invention concerns a creepage control system for locomotives that optimizes adhesion while minimizing wasted energy, rail/wheel wear and shock loading on the drive train. The basis of the invention is to always maintain a small but positive value of the slope of the wheel-rail adhesion creep curve (or differential of adhesion versus creep) for all traction axles of the locomotive through microprocessor control. The value of the differential of adhesion versus creep is used to define an operating window for control and operation of motors continually in the optimum domain when high adhesion is demanded. When, due to a sudden increase in rail contamination, the value of the control function becomes negative, the microprocessor control reduces the generator excitation in stages until the function becomes positive and inside the operating window again. The microprocessor controls a rail cleaning system which is turned on or off depending on the cleanliness of the rail.