A tread device for a retractable step access system for a vehicle includes a tread and at least one wiper device. The wiper device is coupled or couplable movably to the tread and configured in the form of a flap and is arranged and designed to wipe off dirt and to form a ramp by lying, under the force of gravity, on the retractable step. The wiper device is arranged and designed to lie on the retractable step both in an operating state, in which the retractable step is arranged protruding from under the tread, and also in a rest state, in which the retractable step is arranged underneath the tread.