Prevent Trailer/Dock Separation Incidents

Feb. 23, 2012
The nature and characteristics of loading docks vary greatly – from high volume, ultra-modern, multiple-door facilities at logistics centers, to infrequently-used, crudely appointed loading docks at local businesses and schools. However, all of these sites are equally prone to accidents.

Loading dock fatalities and serious injuries occur when there is unwanted separation between the trailer or truck being loaded and the loading dock. Forklift operators are often victims of such incidents when their vehicles fall into the resultant gaps or are driven out of open trailers. In such cases, operators are subject to crushing injuries if the forklift overturns during the fall or collides with the dock apron.

There have been several, excellent studies and articles published relative to USA forklift and loading dock incidents. However, these sources tend to be dated and do not focus on trailer/dock separation incidents. While OSHA and Bureau of Labor statistics have more recent information, data collection methodologies and terminologies do not readily distinguish between trailer/dock separation incidents and other types of forklift-related incidents. A few examples of unclear definitions from various OSHA and BLS databases and summaries appear below:

“Fall from Loading Dock” incidents can include trailer/dock separation incidents—incidents where forklifts fall from vacant docks, or incidents involving workers who fall or jump from docks.

“Struck by Falling Objects or Equipment” incidents can include trailer/dock separation where the forklift falls on the victim, forklift rollovers on the dock or other locations, or incidents where workers are struck by falling freight or objects.

The most current and detailed data relative to trailer/dock separation was found on OSHA’s webpage, “Fatality and Catastrophe Investigation Summary (FCIS)”. This on-line database features searchable, text summaries from OSHA’s fatality investigations. While a more in-depth analysis was possible from reading the text summary of each incident, there were still shortcomings. Many of the individual summaries lacked the detail needed to determine causation. Also, importantly, the FCIS provides summaries for only about 28% of the number of occupational fatalities reported by BLS.

The FCIS database was queried for fiscal years 2002 - 2009 to identify relevant truck loading dock incidents. The following facts were extracted:

  • There were 96 fatal truck loading dock incidents.
  • Eleven of the 96 fatalities involved trailer/dock separation.

Since approximately 28% of USA occupational fatalities are summarized in the FCIS, one can extrapolate that there were around 338 loading dock fatalities during FY 2002 – 2009, thirty-nine of which were related to dock/trailer separation. These estimates can be compared to the BLS Census of Fatal Occupational Injuries (CFOI) that documented 631 forklift-related fatalities for the same period. While the numbers of forklift and loading dock-related fatalities are trending downward, trailer/dock separation incidents have remained constant.

Regulations and Standards

General industry regulations relative to truck loading docks are largely embedded in requirements for Powered Industrial Trucks (1910.178). Specific requirements aimed at preventing trailer/dock separation incidents appear below:

1910.178(k)(1): The brakes of highway trucks shall be set and wheel chocks placed under the rear wheels to prevent the trucks from rolling while they are boarded with powered industrial trucks.

1910.178(m)(7): Brakes shall be set and wheel blocks shall be in place to prevent movement of trucks, trailers, or railroad cars while loading or unloading.

OSHA has issued directives and interpretations that allow alternatives to chocking to prevent trailer/dock separation. Verbiage from a September 14, 2005 letter of interpretation summarizes the Agency’s most current position:

“. . . in light of the changes in technology since the promulgation of 29 CFR 1910.178(k)(1) and (m)(7), OSHA as a matter of policy will regard failure to use wheel chocks or blocks as a de minimis violation and no citation will be issued if alternative methods of preventing truck movement are used. These alternatives may include the use of dock lock mechanisms, dock monitoring systems, or other systems which will prevent the unintentional movement of trucks and trailers while being boarded with powered industrial trucks.”

Violations are common – powered industrial truck citations are the most frequent type of violation in the transportation industry and rank number five for general industry. During FY 2010, OSHA alleged 3868 citations for powered industrial truck violations with proposed penalties of nearly $3.2 million.

Preventing Trailer/Dock Separation Incidents

While there are a number of controls available to help employers reduce the risk of trailer/dock separation incidents, there is no single solution or “best approach”. Providing redundant controls or “layers of safety” is recommended. Final approaches are best defined by local teams that consider the specific risks associated with their truck dock operations.

Trailer/dock separation solutions are divided between administrative and engineering controls. A discussion of these controls and their respective strengths and weaknesses follows:

Administrative Controls:

It would be impossible to safely manage dock operations without administrative controls. But, administrative controls are far from fail-safe since they depend on consistent, favorable, human behaviors. Administrative controls are always subordinate to engineering controls in the risk management hierarchy. Commonly used administrative controls include:

Procedural Controls:

Site-specific procedures are needed to define the actions of dock attendants, forklift operators, and truck drivers. The procedures should specify who is responsible for authorizing access to the loading dock, deploying truck restraint devices or systems, inspecting the trailer and restraint devices, releasing the trailer after loading, and other responsibilities.

Development of contingency plans in the event that the truck restraint device or system is rendered inoperative or defective.

Requiring tractor to be shut-off while positioned at the dock and requiring drivers to remain in a safe, secure area that is remote from their tractor until the trailer has been loaded.

Requiring forklift operators to wear properly adjusted seatbelts to protect them against being thrown from their vehicles in the event of a rollover or trailer/dock separation incident.


Workers should be trained as to specific risks and precautions to be taken to avoid trailer/dock separation. This would include instruction on site-specific procedures and actions to be taken in the event that trailer/dock separation were to occur: don’t jump from vehicle; grasp steering wheel tightly with both hands; brace feet; and, lean away from fall.

Incoming truck drivers should be trained about dock safety requirements before they arrive at the dock.

Wheel Chocks:

Chocks represent the oldest and most commonly used constraint system to prevent trailer/dock separation. While chocks offer advantages of low cost and simplicity, they also present several shortcomings. Their primary vulnerability is a dependence on personnel to properly place and remove the chocks. Even well intentioned dock personnel and truck drivers can become confused or complacent. Tractors can override chocks (i.e., pull trailer over chocks). Even when properly placed, chocks can allow “trailer creep” to occur as forklifts repeatedly enter and exit trailers during the loading/unloading process. Chocks are subject to wear and breakage and can be ineffective in snow, ice, or other slippery conditions.

Preventive Maintenance:

Proper maintenance of forklifts and loading dock equipment (e.g., restraint systems, dock plates and levelers, lights and alarms) is a must for continued, safe operation.

Engineering Controls

As suggested earlier, engineering controls provide a higher level of reliability than when it comes to preventing trailer/dock separation. When properly teamed with procedural and training controls, engineering controls can significantly reduce the probability of trailer/dock separation. Commonly used engineering controls include:

Rear Impact Guard (RIG) hooks:

These devices are secured to loading docks and provide a mechanical or hydraulic means of “hooking” onto the trailer’s RIG (a.k.a., ICC bar). Systems are available from several manufacturers. Costs, features, and reliability vary widely. Advanced systems that include highly visible “Go/No Go” traffic lights and interlocks that will not allow dock doors to open without the presence of a trailer are generally preferred. While RIG hooks are easy to use and offer good protection for many applications, they are not without shortcomings. RIG hooks must be properly installed and maintained and will not work on all trailers. Estimates suggest that 25-70% of trailers cannot be properly restrained by RIG hooks and that they face particular problems with air-ride, low-boy, lift gate, and drop frame trailers. Also, the cost is relatively high and range from ~$7,000 - $15,000 per door.

Wheel locks or wheel engagement systems:

These systems are also manufactured by a variety of firms and are available with different features. They literally “grip” or lock onto a trailer wheel or tandem from a fixed position and won’t allow the trailer to move. Wheel engagement systems will work with most trucks or trailers, including smaller delivery vans. But, as with all of the other systems, they have their disadvantages, including: Comparatively expensive to purchase and install (simple automated systems can cost >$14,000 per door – accessorized installations can run up to $36,000 per door); Can be compromised during snow and ice conditions.

Glad-hand locks:

When the air hose between the tractor and trailer (“glad hand”) is disconnected, air is released from the trailer brakes and the brakes lock mechanically. A glad-hand lock is placed on the connection to assure that the mechanical brakes are not released unintentionally. As with other devices, there are multiple manufacturers and features available including the same types of advanced systems that were described for the RIG hooks. “Trapped key” systems minimize the probability of unauthorized departures. Glad-hand locks are comparatively inexpensive (~$2,000 - $6,000 per door), easy-to-use, and have near universal application.

A potential drawback is the possibility of having tractors drag the trailers while their brakes are locked. A potential drawback is the possibility of having tractors drag the trailers while their brakes are locked. However, drivers should be immediately aware that the brakes are locked because of the increased resistance that would be encountered.


Multiple solutions are available to significantly reduce this risk of trailer/dock separation incidents. Risk reduction requires redundant controls going beyond simple compliance.

Ron Allen is founder of Safety Turnaround Services, a safety consulting firm. He can be reached at 249-649-0463 or [email protected]. His professional career began 37 years ago when he was appointed as Administrator, Technical Services for the American Society of Safety Engineers. Plant, division, group and corporate environmental, health and safety leadership positions followed with FMC Corporation, Monsanto Company, Emerson Electric, Eaton Corporation and Imperial Sugar Company, before recently founding his own firm –Safety Turnaround Services.