Special Combination Vehicle Configurations and Cargo Securement
Special Combination Vehicle Configurations and Cargo Securement tests the configurations beyond the basic van - doubles and triples, tankers, flatbeds, container chassis, auto transporters, saddlemounts - and the securement rules that apply to all of them.
Configurations
- Doubles and triples use a converter dolly with its own fifth wheel, locking pins, and safety chains. They have the strongest rearward amplification, so the last trailer sways most; brake response is slower, and the required endorsement is 'T'.
- Tankers carry liquid that surges; baffles reduce but do not eliminate surge. Watch rollover risk, keep shutoff valves closed, and display the correct placards.
- Flatbeds depend entirely on the load being secured to the deck and, where required, on a header board.
- Container chassis and auto transporters add height, and car carriers carry a high center of gravity; saddlemounts stack tractors and demand wide, slow turns.
Cargo securement basics
- Cargo must not shift, fall, or leak, and must not block lights, reflectors, or the plate.
- The aggregate working load limit of all tiedowns must be at least 50% of the cargo weight.
- Minimum tiedowns: one for articles 5 feet or less in length and 1,100 lb or less; two for anything larger.
- Attach tiedowns to the vehicle's securement points, not to sheet metal or fuel lines.
- Recheck securement within the first 50 miles and every 150 miles or 3 hours afterward.
Worked example
A 20-foot, 3,000 lb steel bundle rides a flatbed. The aggregate working load limit must be at least 1,500 lb, and because the bundle exceeds 5 feet and 1,100 lb it needs at least two tiedowns. Four straps rated at 1,000 lb working load limit each give 4,000 lb aggregate - comfortably over the 50% floor and well above the minimum count - and a header board or forward tiedowns must also stop it from sliding forward under braking.
Traps
- Counting tiedowns without adding up working load limits.
- Assuming the load's weight alone will hold it.
- Forgetting the dolly's safety chains and locking pins on doubles.
- Overfilling a tanker to reduce surge; you need outage space for expansion.