Runway bumpers act similarly to their automobile counterparts:
- They absorb kinetic energy of the crane's impact.
Bridge bumpers should be designed to resist the force resulting from the crane hitting the stop at 40% of the rated speed.
For top-running bridge cranes, a heavy bracket bolted to the top of the runway girder is used as a stop. The bracket either:
- has an attached bumper, or
- is designed to come in contact with a bumper installed on the crane's end truck.
Eventually, the force on the stop is transferred to the building structure and bracing.
