The Dangers Of Dock Shock, Trailer Drop

Spot the warning signs and take action to address these dangerous conditions.


Safety managers have made significant strides in their efforts to improve loading dock safety for semi-trailer truck drivers, forklift operators and anyone who comes into contact with an organization’s shipping and/or receiving areas. Yet despite the progress, two safety issues—known as dock shock and trailer drop—pose serious health and safety risks. The issues also adversely affect the profitability of virtually every facility with a loading dock.

Dock shock and trailer drop are associated with chronic safety issues involving spinal injuries, which are to be avoided whenever and wherever possible. A first-time back injury alone can cost as much as $10,000 when drugs, doctor’s visits and physical therapy are factored into the ailment. One recent study published by Ohio State University reports that severe back injuries that occur when a person is hurt over and over again can cost as much as $300,000.

The key to addressing dock shock and trailer drop is to understand how and why these issues happen. Equally important is the ability to spot signs that the problems exist within a facility, and if so, taking action to address them.

Terminology Defined

Dock shock and trailer drop are terms assigned to unsafe situations that occur during the process of unloading and loading semi-trailer trucks.

Dock shock describes jarring that occurs when a lift truck (stand-up walkie or forklift) crosses between the warehouse floor and the trailer bed due to the bumps and gaps that exist on traditional dock levelers.

Trailer drop describes vertical trailer bed movement or “drop” that occurs with the weight of lift trucks traveling in and out of unstable trailers. The situation is compounded when trailers with air-ride suspension systems are involved as they tend to create increased vertical movement and move away from the loading dock during loading/unloading. Trailer drop causes lift truck operators to experience significant jolts, which can lead to chronic back and neck injuries.

The issues of dock shock and trailer drop came to light when companies expressed concerns about product damage and damage to dock equipment. Also of major concern were the adverse effects that jarring and jolting have on the health of forklift drivers.

Jarring Observed

At virtually any traditional loading dock configuration, lift truck operators encounter significant jarring and jolting as they transfer materials within a facility’s shipping/receiving/staging area and move in and out of trailers.

It soon became clear that no single culprit is responsible for jarring and jolting, which is one of the primary reasons why the problem had often gone unchecked. Instead, the dynamics of lift trucks (both forklifts and stand-up walkies) and their interaction with semi-trailer trucks are a key factor.

This realization dictated the need to further analyze how dock levelers and vehicle restraints influence the situation. Dock levelers serve as a bridge between the dock floor and a semi-trailer. Vehicle restraints are devices that latch onto a trailer’s Rear-Impact Guard (RIG) to keep trailers from separating from the dock during loading/unloading. The restraints help to prevent a variety of catastrophic accidents.

Research showed that a lift truck experiences significant jarring as it encounters bumps and gaps found on standard dock levelers during the loading and unloading process. Subsequent analyses showed conclusively that dock shock serves as a significant source of vibration.

Similarly, research demonstrated that trailer beds move vertically, or “drop,” due to the weight of lift trucks traveling in and out of unstable trailers. Trailer drop is often severe when trailers with air-ride suspension systems are involved because the systems float up and down to maintain a consistent trailer height when loaded or unloaded. The situation causes lift truck operators to experience significant jolts.

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