car retarder[¦kär ri′tärd·ər]
a device for regulating the speed of rail-road cars during shunting operations. Car retarders are most often located on the tracks of hump yards, as well as on in-clined tracks and spurs that lead into industrial plants. Car retarders include the mechanical-shoe type such as pressure-operated retarders, whose braking force is independent of the weight of the car and is transmitted to the wheel by a linkage, and weight-actuated retarders, which operate automatically as a function of the load on the wheel of the car; and the electromagnetic type, in which the braking force is mainly the result of the electromechanical effect. Automatic car retarders, which utilize the electrodynamic principle of operation, are the most advanced. Car retarders of this type are very accurate and can be used both to brake and accelerate cars.