Truck Load Planning: How to Fill a Trailer Without Failing a Weighbridge

Quick answer: Truck load planning is deciding what goes on the trailer, where it sits, and in what order — so the deck fills, the drops come off in sequence, and no axle group exceeds its legal limit. The constraint that stops most loads isn’t deck space or even total payload. It’s how the weight lands on each axle.

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Why a truck is a harder problem than a container

Load a shipping container and you have two limits: the space inside and the payload on the plate. Get under both and the box is legal.

A truck adds a third limit that behaves completely differently. The cargo’s weight is shared between axle groups according to where it sits, and each group has its own legal ceiling. Move a pallet two metres forward and the total weight doesn’t change at all — but the load on the drive axle does.

This is why the classic failure mode is a truck that is:

• under its gross combination weight,
• under the trailer’s payload rating,
• and over the legal limit on one axle group.

Nothing on the packing list looks wrong. The weighbridge disagrees. See truck axle weight limits for the legal figures themselves — this guide is about planning the load so you meet them.

The four constraints a real plan has to satisfy

Constraint	What it limits	Usually binds when
Deck space	Floor area and height	Cargo is light and bulky
Payload	Total cargo weight	Cargo is dense and uniform
Axle groups	Weight distribution	Dense cargo, or anything loaded off-centre
Drop sequence	What can be reached	Multi-stop routes

A plan that satisfies three of four isn’t a plan. It’s a load that gets rebuilt in the yard.

Where the weight should sit

The working rule is that the load’s centre of gravity should sit slightly ahead of the trailer’s axle centreline — roughly over the middle of the deck for a standard tractor-semitrailer.

From there:

• Too far forward and weight transfers over the kingpin onto the tractor’s drive axle. That’s the group that usually goes over first.
• Too far back and the trailer bogie takes it, while the drive axle loses traction — a genuine safety problem in the wet.
• Off to one side and you have a lateral imbalance. Side-to-side limits are tighter than people expect, and an uneven load is a rollover risk on a roundabout.

Heavy cargo belongs low and central, spread along the deck rather than concentrated. A single dense item on a small footprint can also exceed the deck’s local load rating even when the totals are comfortable.

Load order: the part planning software gets wrong

Sequence is a hard constraint, not a preference.

Multi-drop is last-in, first-out. The final delivery is loaded first, at the nose. Anything else means unloading cargo at stop one that belongs to stop three. A planner that optimises purely for density and ignores drop order produces a beautiful, unusable load.

Heavy first, but not at one end. “Heavy at the bottom” is right. “Heavy at the front” is how you overload a drive axle.

Fragile last. Stacking limits are per-item and must be respected, or the bottom layer arrives crushed.

Trailer types and what they change

Different equipment moves the constraints around:

Equipment	Typical deck	Typical payload	Planning note
Curtainsider (13.6 m)	13.62 × 2.48 × 2.70 m	~24,000 kg	Side-loading, so access is easy; still axle-limited
Box trailer / dry van	13.40 × 2.45 × 2.60 m	~24,500 kg	Rear-door only — drop order matters most here
53 ft dry van	16.15 × 2.50 × 2.80 m	~20,000 kg	Long deck, lower payload — usually volume-limited
Flatbed	13.60 × 2.50 m bed	~27,000 kg	No walls: securing and over-width rules dominate
Step-deck	12.50 × 2.50 m bed	~23,000 kg	Lower deck buys height for tall cargo
Box truck (rigid)	7.20 × 2.40 × 2.40 m	~10,000 kg	Two axles only — very sensitive to placement

Figures are typical planning values; your own vehicles’ tare and wheelbase decide the real numbers, which is why any tool worth using lets you configure them.

A rigid vehicle behaves differently from an articulated one: there’s no kingpin, just a front and rear axle, so the load transfers over a much shorter wheelbase and small placement changes swing the numbers hard.

What truck load planning software should actually do

Most tools will show you a 3D trailer with boxes in it. That’s the easy part. The questions worth asking:

• Does it compute per-axle loads, or only total weight? Total weight alone tells you nothing about legality.
• Does it know your rig? Wheelbase, kingpin position, tare and axle positions all change the answer. Generic defaults produce generic — and wrong — numbers.
• Does it respect drop order on multi-stop routes, or does it optimise density and hand you an unloadable sequence?
• When a load fails, does it just warn you? A warning tells you what you already suspect. What you need is the fixed plan.
• Can it print something for the driver? A 2D side elevation the loader can read at the dock beats a model nobody opens.

Fix the load, don’t just flag it

The last point is the one that separates a checker from a planner. Plenty of tools will tell you the drive axle is 400 kg over. Far fewer will tell you what to do about it.

ContainerMath is a container and truck load planner that plans road vehicles as first-class equipment, not an afterthought. It computes centre of gravity on every plan and per-axle weights on road vehicles, checks them against US Federal Bridge Formula or EU Directive 96/53 limits, and — when a load sits over an axle limit — looks for a legal re-stow rather than only warning you, by adjusting alignment, shifting the weight bias, or spreading the cargo over more vehicles. It won’t silently change your drop order, which cargo ships, or the vehicle type: those are your decisions. Weighing it against EasyCargo, Cargo-Planner or CubeMaster? See the container loading software comparison.

You can also build your own vehicle with its real wheelbase, tare and axle layout, so the numbers match the truck in your yard rather than a generic template.

Plan a road-legal load free →

Frequently asked questions

What is truck load planning?

Deciding what cargo goes on a vehicle, where each item sits, and in what order it’s loaded — so the deck is used efficiently, multi-stop deliveries come off in sequence, and every axle group stays within its legal weight limit. It’s distinct from simple cube calculation, which only answers whether the cargo fits.

Why does a truck fail a weighbridge when it’s under the weight limit?

Because gross weight and axle weight are different limits. Cargo weight is shared between the axle groups according to where it sits on the deck, so a load that is comfortably under the total payload can still put one group — usually the tractor’s drive axle — over its own ceiling. Moving the load changes the axle figures without changing the total at all.

Where should the heaviest cargo go on a trailer?

Low, central and spread out. The load’s centre of gravity should sit near the middle of the deck, slightly ahead of the trailer axles. Concentrating heavy items at the front overloads the drive axle; putting them at the back overloads the trailer bogie and costs the drive axle traction.

How do you load a truck with multiple drops?

Last delivery first. Load the final stop at the nose of the trailer and work backwards, so each drop can be unloaded without disturbing the cargo behind it. Getting this wrong means unloading and reloading at every stop.

Do I need software to plan a truck load?

Not for a single uniform product on a familiar vehicle — that’s arithmetic. You need it once loads are mixed, multi-drop, or dense enough that axle limits bind, because axle distribution is genuinely hard to do in your head and is the thing that gets checked at the roadside.

What’s the difference between a rigid truck and a tractor-semitrailer for load planning?

A rigid has only front and rear axles on one chassis, so weight transfers over a short wheelbase and placement changes move the axle figures sharply. A tractor-semitrailer transfers trailer load onto the tractor through the kingpin, so there are three groups to satisfy — steer, drive and trailer — and the kingpin position matters as much as the cargo’s.