the locking of the wheels of a vehicle—for example, a motor vehicle, a streetcar, or railroad rolling stock—while the vehicle is in motion. As a result of such locking, the wheels slide over the bearing surface rather than turn.
A skid occurs when the braking force exceeds the force of adhesion between the wheels and the surface of a road or track, for example, in the presence of glaze ice or after rain. Skidding increases the braking distance and may cause traffic accidents. As a rule, the skidding of the rear wheels of a motor vehicle results in sideslip of the rear axle.
To avoid skids, modern motor vehicles may be equipped with automatic devices that prevent the wheels from locking.