Load Restraint and Load Security
The performance standard
A load restraint system must be able to withstand the forces of heavy braking, acceleration and cornering without the load shifting. The accepted figures are: 0.8 g forward, 0.5 g rearward and 0.5 g sideways, measured against the weight of the load. For a 10-tonne load that means restraining 8 tonnes forward and 5 tonnes in each other direction.
Methods
Containment uses the vehicle body - headboards, gates, stakes, dropsides - to block movement. Blocking places timber or purpose-made structures against the load. Direct lashing attaches the load to the vehicle. Tie-down lashing presses the load onto the deck so friction holds it, and relies on having enough tension and enough friction between load and deck.
Curtains do not restrain a load; they are weather protection only.
Capacity and angles
Each component has a lashing capacity (LC) and a pre-tension. Aggregate capacity must exceed the force required. Angles matter: a lashing running at 45 degrees to the direction of the force contributes only about 70 per cent of its capacity, so you need more lashings, not longer ones.
Traps
Questions test whether you count the load's weight rather than its rated capacity, whether you assume curtains are restraint, and whether you allow for friction only when it can be justified.
Worked example: a 12-tonne excavator on a drop deck needs 0.8 x 12 = 9.6 tonnes of forward restraint. Chains rated at 5 tonnes LC each, running at 45 degrees, contribute about 3.5 tonnes each, so two chains are not enough - three gives you about 10.5 tonnes and is the minimum acceptable arrangement, plus a check that the bucket is secured.