Compressed air is used to impede the locomotive, which has a set of brakes completely separate from the rest of the train. From the air pumps (or an air reservoir), air is pumped to a pair of cylinders at each wheel. By pushing against each other, these brake cylinders move curved metal "arms" toward the tire tread, pressing brake shoes tightly against the wheels. Friction does the rest.
Quick facts
Look, Ma, no brakes
First use in England
First use in United States