The railyard organizes trains on the hump, which is a hill that train cars are pushed up and decoupled at the top. The cars then roll down the other side of the hump and are switched to different tracks. Retarders are used on the downward slope of the hill to control the speed of the cars by compressing the wheels between the beams that are lined with braking material. Air cylinders along the retarder force the beams against the wheels.