Cargo Securement and Weight Limits
This domain tests the rules that keep a load on the truck and the truck under legal weight. Expect arithmetic: aggregate working load limit, number of tiedowns, axle weights, and the federal bridge formula. The driver is responsible, not the shipper, for a legal and secure load.
Securement rules
- 49 CFR 393.100 through 393.136 govern securement. Cargo must be secured against forward, rearward, side-to-side, and vertical movement.
- The aggregate working load limit of all tiedowns must be at least 50 percent of the cargo weight.
- Articles longer than 5 feet and heavier than 1,100 pounds need at least two tiedowns; longer or heavier loads need more.
- Working load limit is not breaking strength. A chain rated at 5,400 pounds WLL is not a 5,400-pound breaking point.
- Cargo must not block lights, reflectors, placards, or the license plate, and must not interfere with the exhaust or the steering.
Weight limits
- Federal limits: 80,000 pounds gross vehicle weight, 20,000 pounds on a single axle, 34,000 pounds on a tandem axle group.
- The bridge formula limits how much weight can be carried over a given span based on the number of axles and the distance between them; you can be legal on gross weight and illegal on an axle.
- Follow posted bridge and route restrictions in the District and stop at weigh stations when signals direct you.
Worked example
A 46,000-pound load of steel coils must be secured. Reasoning: 50 percent of 46,000 is 23,000 pounds, so the combined WLL of the tiedowns must reach 23,000. Four chains at 5,400 pounds each give 21,600 pounds - short. Add a fifth chain or use higher-rated tiedowns, and confirm the floor anchors are rated for the load.
Traps
- Confusing working load limit with breaking strength.
- Assuming a legal gross weight means every axle is legal.
- Relying on the shipper's paperwork instead of checking the load yourself.