A load on a vehicle has to stay put under braking, cornering and acceleration. BS EN 12195-1:2010 gives the design accelerations and the calculation methods for road transport.
Forces to restrain
For road transport the standard uses accelerations, as a fraction of the load's weight, of 0.8 g forward, 0.5 g rearward and 0.5 g sideways, with 1.0 g vertically. A 10 t load therefore needs restraint equivalent to 8 t forward. Friction between load and bed provides part of it; lashings, blocking and the headboard provide the rest.
Friction
Friction depends on the two surfaces in contact. Steel on steel is low; anti-slip mats raise it considerably. Friction cannot be relied on unless the surfaces are clean, dry and free of ice, oil or loose material.
Tie-down and direct lashing
- Tie-down (top-over) lashing presses the load onto the bed and increases friction. Its effect depends on the pre-tension in the strap (STF) and the lashing angle. It suits loads with good friction and low centres of gravity.
- Direct lashing connects the load to the vehicle so the lashing itself takes the force. Its effect depends on the lashing capacity (LC) and the angles. It suits heavy machinery and steel.
Reading a label
EN 12195-2 webbing labels give the lashing capacity LC in daN (1 daN ≈ 1 kg force) and the standard tension force STF achieved with the ratchet. Chains (EN 12195-3) and wire ropes (EN 12195-4) carry their own markings. The weakest component — strap, chain, tensioner or anchor point — limits the lashing.
Minimum number of tie-downs
Independently of the force calculation, many rules set a minimum number of tie-downs by the length and weight of the article; for example one for a short, light article, two for longer or heavier articles, and one more for each additional 3 m or so of length. Use whichever gives more lashings.
The lashing calculator runs the EN 12195-1 force checks and the tie-down count rules together, selects the equipment and produces a compliance report and pre-trip checklist.
General guidance only. It does not replace the manufacturer's data, the applicable standards or the judgement of a competent person.