Cargo does not stay put by itself
A load that looks stable on a loading dock is about to meet forces it has not yet felt. Vehicles accelerate, brake, turn, climb, bounce and vibrate, and each of these tries to move the cargo relative to the vehicle. Friction and the weight of the goods hold things in place up to a point; beyond that point, items slide, tip or fall. Load securing is the practice of adding restraints, blocking or friction so that cargo stays where it was put.
The aim is two things at once: keeping people on the road safe, and keeping the goods undamaged. Poorly secured loads can injure people and cause accidents, so the rules for securing are often set by law, and they differ between countries and modes.
The forces involved
Braking and acceleration. When a truck brakes, cargo tends to continue forward. Hard stops are the classic cause of loads sliding toward the front of the trailer.
Cornering. In a turn, cargo tends to move outward. Tall, narrow loads with a high center of gravity are particularly likely to tip.
Vibration. Continuous small shaking from the road, rail joints or engines can cause packages to creep, settle or rub. Over a long trip, vibration can loosen loads that were tight at departure and abrade surfaces.
Shocks and impacts. Potholes, rail coupling, crane drops, and forklift bumps deliver sudden loads.
Ocean and air motion. Ships roll and pitch and can be subject to heavy weather, so loads in ocean shipping face much larger and longer movements than on a smooth road. Air freight typically has gentler motion in flight but involves frequent handling at each end.
Exact force levels depend on the vehicle and conditions, and securing standards define the figures to be used for planning. Those figures are best taken from the relevant regulation or standard.
Typical causes of damage
- Shifting. Loads that slide into the walls, doors or each other.
- Crushing. Heavy items placed on weak ones, or stacks too high for the package’s strength.
- Voids. Empty spaces in a trailer or container that let cargo move.
- Poor weight distribution. Concentrated weight on one part of the floor or axle can damage the vehicle and shift stability.
- Unsuitable packaging. Packaging not made for the journey fails first.
- Moisture and condensation. Water damage from rain, leaks or condensation inside a container, which can ruin paper, cardboard and metal parts.
- Improper handling. Dropping, dragging and forklift punctures happen at the dock more often than in the vehicle itself.
Basic ways of securing a load
Methods are usually combined.
Blocking. Solid items such as wooden beams or other fixed supports are placed against the cargo so it cannot slide. Blocking works well because it does not depend on friction.
Bracing. Supports are placed between cargo and the vehicle structure to keep items from tipping or moving sideways.
Lashing and tie-downs. Straps, chains or ropes pull the cargo against the vehicle or hold it in place. They must match the load: the strength rating of the strap, the anchor points and the angle all matter.
Friction increase. Anti-slip mats or rough materials between the cargo and the floor raise resistance to sliding.
Dunnage and void fill. Air bags, foam, cardboard or timber fill gaps so there is no room for movement inside a container.
Unitizing. Binding goods into a single stable unit with stretch wrap, straps or bands makes them behave like one object. Pallets and unit loads are the usual form. A well-built pallet that is tightly wrapped is much less likely to lose a carton in transit.
Loading choices that help
- Place heavy items low and light items on top.
- Keep the load balanced side to side and over the axles.
- Fill gaps rather than leaving voids, and avoid overhanging pallet edges.
- Load in a way that suits the order of delivery, so that unloading does not disturb the remaining goods.
- Do not rely on a closed door to hold a load. Doors can be pushed open or damaged by cargo that has shifted, and a load leaning on a door can fall out when it opens.
For shared trailers carrying several shippers’ goods, freight consolidation and LTL shipping involve more handling and mixed cargo, so the packaging and securing need to withstand being moved and re-stacked.
Special cargo
Some freight needs special thought. Liquid loads can slosh, which creates forces that surge through a tank. Loose bulk cargo can settle and shift. Very large or heavy equipment, treated as project cargo, typically needs engineered lashing plans. Chemicals classed as hazardous materials may have specific stowage and segregation rules. In all of these cases the relevant regulation or an expert should guide the plan, not general rules of thumb.
Intermodal considerations
When freight moves in a container from truck to rail to ship, it faces more handling than a single road journey. Under intermodal transport, a load that is acceptable for one short trip may not suit a trip with several transfers, and the securing should be designed for the roughest leg.
Checking and recording
Good operators inspect the load before departure and, on longer trips, recheck it after the first stretch, because straps loosen as cargo settles. Photographs of the loaded state create a record that helps if a dispute later arises. The process of documenting and claiming for loss is covered in freight claims, and records of condition at loading are central to it.