§393.100 is the general cargo-securement rule: cargo must be firmly immobilized or secured on or within a vehicle by structures of adequate strength, dunnage or dunnage bags, shoring bars, tie-downs, or a combination thereof. The detailed working-load-limit math is in §393.102 and the commodity-specific requirements run through §393.116–§393.136.
The 50% / 80% / 60% rule (§393.102)
The total working load limit (WLL) of tie-downs must be at least 50% of the cargo weight. Working load limit per tie-down equals one-third of breaking strength (chain) or one-quarter (synthetic web).
The vehicle structure (headboard, walls, decking) must withstand:
- 0.8 g forward deceleration
- 0.5 g rearward acceleration
- 0.5 g lateral acceleration
These are the underlying numbers behind the "adequacy" finding the roadside inspector applies.
OOS criteria
Inadequate securement that creates an immediate hazard (cargo overhanging, tie-downs slipped, shifting visible) places the vehicle OOS until the load is re-secured to specification.
How to prevent it
- Train drivers on the §393 Subpart I working-load-limit math for the specific commodities they haul.
- Equip every tractor with a securement-aid kit (chains, binders, straps, edge protection) appropriate for the typical loads.
- Inspect tie-downs at the first stop after loading; loads settle in the first 50 miles and tie-downs slacken.
How Roadworthy HQ helps
§393 securement findings link to the vehicle and driver and live in the audit binder. Pattern findings on the same driver are documented for the §391.25 annual-review trail.