Forklifts can plunge to a lower level if the trailer separates from the dock during loading/unloading. This is often a very serious and sometimes fatal accident.
"Trailer creep" occurs when the truck/trailer gradually moves forward because of forklift braking/rocking/impact as the forklift shuttles in and out. The forklift operator is likely not to be aware that creep is occurring until it’s too late. Also, truck drivers may pull away too early because of miscommunication, impatience ("time is money"), lapse of attention, or whatever. For these reasons, precautions to secure the trailer are essential.
Brakes are the first line of protection. Most over-the-road trailers are equipped with spring brakes that apply when air pressure is released. Brakes help protect against creep, but chocks or "dock-locks" need to be used in addition to brakes.
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