Vehicle restraints were invented to help stop horrific incidents in which a forklift tumbles from a loading dock, crippling or killing its driver. For nearly three decades, they have done that job well.
But today, vehicle restraints do even more. They make loading docks more productive and support efficient supply chains. And the latest restraints also reduce the risk of neck and back injuries to forklift drivers by reducing trailer drop, which is vertical trailer bed movement due to the weight of forklifts traveling in and out of trailers that can jolt forklift operators.
As such, restraints play a strategic role as part of ergonomic docks designs that protect employee health and wellness. In their original function, they secure trucks of virtually any size, shape, height and configuration to the loading dock, while also helping to prevent trailer-separation accidents.
Given all these advantages, the selection of vehicle restraints is a business decision that deserves attention from multiple functions: warehousing and logistics managers, safety directors, operations management and executives. A restraining system that fits the work environment contributes to a safe workplace, a competitive supply chain and strong business performance.
Simple Beginnings
Vehicle restraints emerged because wheel chocks proved ineffective for holding trailers at the dock during loading. Plant personnel observed that trailers could“creep” away from the dock with repeated jolts from forklifts, until a gap opened at the dock edge. The forklift and driver then could fall to the pavement, often with catastrophic results.
Besides being unreliable and prone to slipping on snow or ice, wheel chocks provided no signal to let forklift operators know when they safely safely load, or to tell truckers when they safely could depart. As a result, truckers sometimes pulled trailers away while a forklift was entering, again causing serious incidents.
The first vehicle restraints addressed the problem effectively. When a truck backed in, a hook inside a wall-mounted housing rotated up to grab the rear impact guard (RIG), holding the truck in place. Forklift drivers saw a flashing green light when the truck was secure, and flashing red when it was released. Truckers, meanwhile, saw a red light when the truck was engaged, and green light when it was released and they were cleared to leave.
This configuration, built on national survey of thousands of trailers and 5 years of development, worked on some 95 percent of trucks. In 1981, OSHA recognized the system as an acceptable alternative to wheel chocks. Companies of all sizes and across nearly all industries adopted the technology, which became fundamental to dock designs.
Changing Landscape
Then life at the loading dock began to change. Through the 1980s, companies pushing for more efficient supply chains moved toward trucks that could carry bigger payloads. They switched to low-profile tires and rims to increase box size without increasing clearance height. They adopted air suspensions to cushion the ride, protect cargo and extend trailer life.
The new trailers — longer, wider and taller, and with lower beds — created challenges for lift truck drivers. At the same time, companies demanded more productivity on the dock. Faster servicing of new trailers carrying wider, taller loads added to safety concerns.
Vehicle restraints had to adapt, holding on to RIGs at the typical 30 inches above the road, yet reaching down to secure low-bed trailers with RIGs as low as 12 inches above the ground. Modifications such as a low-profile “nose extension” on the restraint housing provided the necessary working range.
Adding complexity, trucks were introduced with hydraulic rear lift-gates for use at facilities that had no dock levelers. These units had no RIGs for traditional restraints to grab. Manufacturers therefore developed wheel-locking restraints. As the truck backs in, a barrier rod deploys and is automatically positioned against and ahead of a rear tire. These restraints can secure virtually every trailer.
Gaining Prominence
As years passed, supply chain efficiency became universally recognized as a key to competitive advantage. Business leaders now saw a safe, productive loading dock as a key link in the distribution chain.
Yet new hazards emerged at the loading dock. The bed height of trailers with air-ride suspensions could fluctuate by several inches as lift trucks added or removed loads. Such trailers also could bounce with the weight of loads and progressively “walk” away from the dock. The bouncing could cause some restraint designs to lose their grip on the RIG.
Other dangers emerged with trailers spotted at the dock and supported by landing gear. Lift truck traffic could rock the trailer until the landing gear collapsed, causing the trailer to pitch forward or fall to the side. In another scenario, the weight of a lift truck at the trailer's front end could force the nose down and the back end up and away from the building. In another dangerous situation, with the tandem wheels in a forward position, a lift truck entering could cause the rear of the trailer to scoot forward and drop. This in turn causes the trailer nose to pop up.
Now, vehicle restraints had to do more than resist trailer movement straight out and away from the building. In effect, they had to trap the RIG so that it could not move outward, rise up or tip to the side. Progressive manufacturers responded with improved rotating hook designs, ensuring that the hook “wraps around” the RIG, providing two-point entrapment to protect against every known form of trailer separation.
Addressing Ergonomics
More recently, industry observers have looked beyond catastrophic incidents at the dock and focused on the need to address long-term wellness issues, including the risk of chronic spinal injuries to lift truck drivers.
Analysis of the trailer loading and unloading process showed that trailer beds move vertically, or drop, from the weight of lift trucks traveling in and out. The problem of trailer drop especially is severe in trailers with air-ride suspensions. Trailer drop means forklift drivers experience a significant jolt to the neck and spine every time they enter a trailer, which they may do hundreds of times in a daily work shift.
The risk of injury is significant, and so are the potential costs. Studies by the National Institute for Occupational Safety and Health (NIOSH) report that shock (jarring and jolting) causes 36 percent of all head, neck and back injuries associated with mobile equipment operators.
Meanwhile, the National Safety Council reports that one-fourth of workplace illnesses and injuries in the United Sates are back related, and the American Society of Orthopedic Surgeons states that back injuries are the most costly medical condition in the nation. Back injuries are estimated to cost U.S. companies billions per year.
A first-time back injury can cost up to $10,000 in doctor visits, medication and physical therapy. One recent study published by Ohio State University showed that more-severe back injuries occurring when a person repeatedly is hurt can cost up to $300,000.
The latest innovation in trailer restraints addresses this issue. Introduced in 2005 as a new category of restraint, the device stabilizes the trailer and helps prevent both vertical and horizontal movement. Specifically, the restraint provides vertical support to the trailer with hydraulic cylinders that resist downward movement as lift trucks enter. Additionally, the design uses a rotating hook to prevent accidents caused by trailer separation.
The restraint reduces the average trailer deflection under the weight of a lift truck to a maximum of 2 inches up or down, versus an average of 6 inches up or down without vertical support. That equates to a two-thirds reduction in trailer drop. The stress on lift truck drivers significantly is reduced, and so is the risk of back and neck injuries. And by stabilizing the trailer, product and equipment damage resulting from trailer drop also is reduced.
Since its introduction, the advanced restraint has been increasingly popular in a wide range of industries due to its ability to provide a smooth transition between the dock floor and trailer.
Exceeding Expectations
Vehicle restraints have made major contributions to material handling safety. Their versatility and benefits have gone far beyond what the inventors envisioned nearly three decades ago.
In preventing serious workplace incidents, in adapting to sweeping changes in the loading dock environment and in reducing occupational injuries and disabilities with their attendant costs, vehicle restraints have become more essential than ever for companies seeking a safe route to strong business performance.
Joe Manone is vice president of Rite-Hite Corp., a manufacturer of vehicle restraints and material handling systems headquartered in Milwaukee, Wis.