• Tiedowns are an important part of a safe trucking operation because they prevent the shifting or loss of cargo.
• Knowing the working load limit of the securement system is key to securing cargo.
• Regulations do not require tiedowns to be marked or labeled.

The cargo securement requirements of the Federal Motor Carrier Safety Regulations specify how — and how many — cargo tiedowns are to be used. Tiedowns include chains, ropes, webbing, steel straps, binders, buckles, and other devices that can be used to secure cargo. Subpart I of 49 CFR Part 393 Tiedowns are an important part of a safe trucking operation because they prevent the shifting or loss of cargo.

Working load limits (WLLs)

A key concept when working with tiedowns is their “working load limit” (WLL) which indicates how strong they are and thus how much cargo they can secure. The WLL is the maximum load that may be applied to a tiedown or other component of a cargo securement system during normal service. The WLL is usually assigned by the manufacturer of the component and is generally equal to one-third (or in some cases one-fourth) of the ultimate breaking strength of that device.

The WLL of a tiedown, associated connector, or attachment mechanism is the lowest WLL of any of its components (including tensioner), or the WLL of the anchor points to which it is attached, whichever is less. For example, if a chain has a WLL of 6,600 pounds but the binder used on that chain has a WLL of 5,000 pounds, the WLL for that tiedown device is 5,000 pounds. This is based on the idea that the securement system is only as strong as its weakest component.

Determining the WLL of a tiedown

The regulations do not require tiedowns to be marked or labeled. However, manufacturers of tiedowns and associated equipment are encouraged to provide motor carriers and enforcement officials with a means to easily determine the working load limits of their products.

The WLLs may be determined by using either:

• The tiedown manufacturer’s markings on the device, or
• The tables in 393.108.

The WLLs listed in the regulation must be used when the tiedown material is not marked with a WLL by the manufacturer. If the value in the regulation is different from the manufacturer’s marking, employees should use the marked value. Note that an unmarked chain is assumed to be Grade 30.

Aggregate WLL

Another key factor when using tiedowns is their combined or “aggregate” WLL. The aggregate WLL of any securement system must be at least one-half times the weight of the article(s) being secured. For example, the tiedowns used to secure cargo weighing 30,000 pounds must have an aggregate WLL of 15,000 pounds. The aggregate WLL is determined by adding together:

1. One-half (50 percent) of the WLL of each tiedown that goes from an anchor point on the vehicle to an anchor point on an article of cargo;
2. One-half (50 percent) of the WLL of each tiedown that is attached to an anchor point on the vehicle, passes through, over, or around the article of cargo, and is then attached to an anchor point on the same side of the vehicle; and
3. The full (100 percent) WLL for each tiedown that is attached to an anchor point on the vehicle, passes through, over, or around the article of cargo, and then attaches to another anchor point on the other side of the vehicle.

Note that additional tiedowns may be needed based on the shape, length, and placement of the cargo.