In this chapter, the reader is introduced to track brakes. Track brakes do not act on the wheels or wheelsets and thus may yield additional braking force under the presence of lower adhesion. This is achieved by help of a vertical magnetic force between track brake and rail. The additional vertical forces as well as the horizontal forces achieving the retardation need to be borne by the bogies. For low velocities, the friction coefficients rise steeply and the resulting forces may exceed the strength of the bogie frame and the track brake.