A crane buffer is a hydraulic device that has the characteristics that it extends easily under its own internal spring but, on compression, the device reacts with a large damping force. The disadvantage of using a hydraulic device is that they are expensive and a monitoring program must be implemented to ensure that the devices are always operable. Buffers or stops are placed at the ends of sections of travel trackage, but the crane is not supposed to strike them. If the crane should suffer the high deceleration accompanying a buffer strike, it would surely overturn. Instead automatic brake trappers are placed at a distance from the buffers. The buffers serve only in the event that the brakes fail to stop the crane fully in the allotted distance.