When properly securing cargo to a flatbed or step deck trailer, there are specific logistics challenges, i.e., how to safely load, secure and transport unique items that, because of size, shape and weight, can only be transported on this type of trailer. Specific regulations of the Federal Motor Carrier Safety Administration (FMCSA) must be followed.
In January 2004, FMCSA issued new rules on how to secure different types of loads, which include all cargo-carrying commercial motor vehicles operated in interstate commerce. This regulation covers all types of cargo, except commodities in bulk such as seed, grains, liquids, gases, liquid concrete, sand, gravel, and aggregates that lack structure or fixed shape and are transported in a tank, hopper, box, or similar device that forms part of the structure of a commercial motor vehicle.
FMCSA developed specific performance requirements for all secured loads. This covers deceleration in the forward direction, and acceleration in rearward and lateral directions (left, right, and upward) that cargo securement systems must withstand. Deceleration is the rate at which the vehicle’s speed decreases when the brakes are applied, and acceleration is the rate at which the vehicle’s speed increases in the lateral direction or sideways (while the vehicle is turning), or in the rearward direction (when the vehicle is driven in reverse and contacts a loading dock).
Math and science help explain the cargo securement regulations.
Acceleration and deceleration values are commonly reported as a proportion of the acceleration due to gravity (g). This acceleration is about 9.8 meters/second/second (32.2 ft./second/second), which means that the velocity of an object dropped from a high elevation increases by about 9.8 meters/second (32.2 ft./second) each second it falls. FMCSA requires cargo securement systems withstand the forces associated with three deceleration/accelerations, applied separately:
- 0.8 g deceleration in the forward direction
- 0.5g acceleration in a lateral direction, and
- 0.5 g acceleration in the rearward direction.
Based on researchers’ analysis of trucks and trailer performance, the highest deceleration likely for an empty or lightly loaded vehicle with an antilock brake system, all brakes properly adjusted, and warmed to provide optimal braking performance is in the range of 0.8-0.85 g. However, a typical, loaded vehicle would not be expected to achieve a deceleration greater than 0.6 g on a dry road.
The typical lateral acceleration while driving around a curve or on a ramp at the posted advisory speed is in the range of 0.05-0.17 g. Loaded vehicles with a high center of gravity roll over at a lateral acceleration above 0.35 g. Lightly loaded vehicles or heavily loaded vehicles with a lower center of gravity may withstand lateral acceleration forces greater than 0.5 g.
Generally, truckers and trucking companies aren’t required to conduct testing of cargo securement systems to determine compliance with the performance requirements. The new FMCSA rules explicitly state that cargo immobilized or secured in accordance with the general securement rules, or the commodity-specific rules, are considered to meet the performance criteria. Securing cargo correctly is important not only for the trucker’s safety and all who cross his/her path, but improperly secured loads are costly both in dollars and your CSA score.
There are several areas of concern when designing the method by which to secure loads placed on a trailer. Each different type of trailer and cargo requires a cargo securement system. A “securement system” is a method that uses one or a combination of the following three elements:
One: Vehicle Structure
What is included? Floors, walls, decks, tiedown anchor points, headboards, bulkheads, stakes, posts, and anchor points. All parts of the vehicle structure and anchor points must be strong enough to withstand the following forces:
Forward force: 0.8 g (80%)
Rearward force: 0.5.g (50%)
Sideways force: 0.5 g (50%)
Upward force: 0.2 g (20%)
It’s also important to inspect all vehicle cargo securement elements prior to each use to ensure there is no obvious damage, no distress, and no weakened parts or sections.
Two: Securing Devices
What’s a securing device? Any device specifically manufactured to attach or secure cargo to a vehicle or trailer, e.g., synthetic webbing, chain, wire rope, manila rope, synthetic rope, steel strapping, clamps and latches, blocking, front-end structure, grab hooks, binders, shackles, winches, stake pockets, D-rings, pocket, webbing ratchet, bracing, and friction mat.
What’s a tiedown?
Tiedowns are devices that are used to fasten or secure a load to a carrier by use of ropes, cables or other means to prevent shifting during transport. Some tiedowns are attached to the cargo and provide direct resistance to restrain it from movement. Other tiedowns pass over or through the cargo to create a downward force that increases the friction between the cargo and the deck of the trailer or truck. The friction restrains the cargo.
A tiedown must be designed, constructed, and maintained so that it can be tightened by a truck driver. The only exception to this is the use of steel strapping. All components of a tiedown must be in proper working order—no knots or obvious damage, no distress, no weakened parts or weakened sections. Each tiedown must be attached and secured so that it does not become loose or unfastened and does not open or release during transit.
All tiedowns and other components of a cargo securement system must be located within the rub rails (when present). Edge protection must be used if a tiedown could be cut or torn when touching an article of cargo. The edge protection itself must also resist crushing, cutting, and abrasion.
Three: Blocking & bracing for securing cargo
The material used for blocking or bracing and as chocks or cradles must be strong enough to withstand being split or crushed by the cargo or its tiedowns. This also applies to any material used for dunnage. If wood is used, hardwood is recommended. It should be properly seasoned—no green wood. It should be free from rot or decay, knots, knotholes and splits or any damage that would compromise its strength. The grain should run lengthwise when using wood for blocking or bracing.
Cargo must be firmly immobilized or secured on the flatbed/step deck by structures of adequate strength, dunnage (loose materials used to support and protect cargo), shoring bars, tiedowns or a combination.
In other words, your freight becomes a part of the trailer through the use of dunnage, shoring bars, tiedowns, straps, chains, etc., or a combination of all of these to the point where the freight only moves as one with the trailer.