Research presented at an OPTIMA seminar by Elsa Silva shows the fixes cost far less capacity than most operators assume, and that they will not happen by accident.
Picture a Tuesday at a furniture distributor. The rigid truck is loaded the way it always is: heaviest items over the rear axle where the forklift can reach them, everything squared off, wrap on, about 15 tonnes on board. The driver checks the plate, the total is under the limit, and the truck leaves.
The first customer takes the two heavy lounge suites from the back. The truck is now carrying 10 tonnes. Nobody thinks twice, because a lighter truck is a safer truck.
Except that it is not.
With the rear weight gone, the remaining load sits well forward, and at 10 tonnes with that much weight over the cab, the front axle is now carrying more than the manufacturer rates it for. The steering and braking behaviour has changed. If the truck is weighed at the next site, or is involved in an incident, the business is the one explaining why a compliant departure became a non-compliant vehicle at the first stop.
Same truck, one drop later
Departure · 15 t Inside safe zone
After drop 1 · 10 t Front axle over rating
Illustrative. The two heavy lounge suites at the rear (highlighted) come off first. The lighter load now sits further forward.
That example is Silva’s own, from her OPTIMA seminar Beyond Geometry: Optimising Cutting and Packing in Practice. [1] Silva is an operations researcher at the University of Minho in Portugal who has spent years building loading and cutting models with real companies: a Port wine exporter, a textile plant, a fuel distributor.
Her message to industry is simple. The academic field has spent decades on how to fit the most into the least space. The things that actually cost businesses money and put people at risk are pallets that collapse, trucks that breach axle limits, and cutting plans that look efficient on paper and cause chaos on the floor. None of that shows up in a plan unless someone deliberately puts it there.
This article sets out what her work means for a business that moves goods, in plain terms first. The mathematics and the published papers are at the end for anyone who wants to go deeper.
Why this matters to your business
Getting a load wrong costs money in four places, and most businesses only track one of them.
-
Damaged stock
A pallet that shifts in transit means write-offs, credits, re-deliveries and a customer who remembers. The standard failure: column-stacked cartons, wrapped, leaning and then down. [1]
-
Injured people
The same collapse lands on whoever opens the trailer door. Interlocking is used in practice precisely to reduce product damage and the risk of injury to people handling the pallet. [4]
-
Compliance exposure
Axle mass limits are law, and being under the gross limit is not the same as being compliant. Under the Heavy Vehicle National Law, chain of responsibility duties extend to the parties who pack, load and consign.
-
Wasted space
The one everyone measures, and the reason the other three get neglected. Teams resist stability and balance rules because they assume the rules cost cube.
The most useful thing in Silva’s work is evidence that they mostly do not. Across her cases, the pattern repeats. When a safety or handling rule is left out of the plan, the plan breaks it a large share of the time. When the rule is built into the plan from the start, the capacity given up is small, and in the pallet case almost nothing. [1,2,4]
In other words, the trade-off most businesses believe they are making does not exist at the size they think it does. The rest of this article works through the five examples behind that claim, each with what it means on the floor.
Example 1 · Pallets
The stable pallet costs one case in fourteen plans
The pallet work started with a Port wine exporter. Cases of wine, all the same size for a given product, had to be stacked onto pallets, and the company wanted as many cases per pallet as possible. [1] Every manufacturer shipping a single SKU on a pallet, from cartons of tiles to flat-pack furniture, has the same problem.
The layout that fits the most cases is usually a column stack: every layer identical, every case directly on top of the one below. It is also the layout that falls over. Anyone who has run a warehouse knows the fix. You interlock: rotate or mirror each layer so the cases overlap the joints below, the way a bricklayer staggers a wall. Silva is blunt that stretch-wrap on a column stack does not reliably hold it in a moving truck. [1]
What the warehouse does not know is what interlocking costs in cases per pallet, and that is what the research measured. Araújo, Ramos, Silva and Moura built a planning model that requires the case orientation at each corner of the pallet to change between one layer and the next, then ran it across 532 different pallet and case combinations. [1,4]
- 494 combinations: interlocking cost nothing
- 38 : cost one case in a layer
532 pallet and case combinations · never more than one case lost [1]
On the standard measure of how many cases are boxed in by their neighbours, the interlocked plans scored far higher than the plans that chased occupancy alone. [1]
Example 2 · Vehicle balance
Your truck has a safe zone, and total weight does not tell you where it is
Ask most loading supervisors whether a truck is safe and they will tell you the total mass and compare it to the gross limit. That answers one question. It does not answer whether the front axle is overloaded, whether the rear axle is overloaded, or whether there is enough weight on the steering axle for the driver to keep the truck pointed where they want it.
- Weight distribution How the mass is spread across the floor. Matters for the floor.
-
Load balance
Where the load’s centre of gravity sits along the vehicle. Matters for steering, braking and axle loads, and most loading tools ignore it. [1,2]
Every vehicle has a safe zone for its centre of gravity, and it is not a single number. It depends on how much is on board. The manufacturer’s data (tare weight on each axle, wheelbase, maximum front and rear axle loads, gross limit, and the minimum weight that has to stay on the steering and drive axles) can be turned into a diagram. On one axis is where the centre of gravity of the load sits, on the other is how much load there is, and the diagram shows the region where every legal and technical limit is met at once. [1,2] Silva calls it the load distribution diagram.
