Truck weights: gross vehicle, gross combination and axle loads

A loaded articulated combination carries at least four different weights, and the one that stops an operator at a roadside check is rarely the one printed in the brochure. Gross vehicle weight, gross combination weight, payload and individual axle loads are separate figures governed by separate rules. A combination can sit comfortably under its gross limit, be plated correctly, and still be an offence because too much of the load has ended up on one axle.

The four numbers and what each one is for

Tare weight — kerb or unladen weight — is the vehicle as delivered: chassis, cab, fifth wheel or body, fuel, AdBlue and usually a nominal driver. It is the only figure here you cannot change after the truck is built, which is why it quietly decides everything downstream.

Gross vehicle weight (GVW, or GVM) is the most the vehicle itself may weigh when loaded. On a rigid that includes body and cargo. On a tractor unit it means the imposed load coming down through the fifth wheel from the semi-trailer, which is normally the largest single load the tractor carries.

Gross combination weight (GCW), also called gross train weight, is tractor plus trailer plus everything on both. This is the number people mean when they say “forty tonnes”.

Payload is the remainder: permitted GCW, minus the tare of the tractor, minus the tare of the trailer. It is derived rather than rated, which is why no manufacturer publishes it as a specification — it depends on the trailer you couple to. Every kilogram added anywhere in the combination, whether a bigger fuel tank, a third axle or a battery pack, comes straight out of it.

What the EU rules actually say

For international traffic within the EU the limits come from Council Directive 96/53/EC, and its Annex I is worth reading once rather than being quoted at second hand.

The gross figures are the familiar ones. A two-axle motor vehicle is limited to 18 tonnes; a three-axle motor vehicle to 25 tonnes, or 26 tonnes where the driving axle is fitted with twin tyres and air suspension or a recognised equivalent. An articulated vehicle or road train with five or six axles is limited to 40 tonnes. In intermodal work carrying a 45-foot container or swap body, a two-axle tractor with a three-axle semi-trailer is allowed 42 tonnes, and a three-axle tractor with a two- or three-axle semi-trailer 44 tonnes. A three-axle articulated bus is 28 tonnes.

The axle figures are the ones that catch people out. A single non-driving axle is limited to 10 tonnes and a driving axle to 11.5 tonnes. Bogie limits then depend on how far apart the axles sit. On a trailer or semi-trailer, a tandem set is limited to 11 tonnes where the spacing is under one metre, 16 tonnes from one metre to 1.3, 18 tonnes from 1.3 to 1.8, and 20 tonnes at 1.8 metres and above. A tri-axle bogie is limited to 21 tonnes up to 1.3 metres and 24 tonnes between 1.3 and 1.4. On the motor vehicle itself a tandem set runs 11.5 tonnes under a metre, 16 tonnes to 1.3, and 18 tonnes to 1.8 — 19 tonnes where the driving axle has twin tyres and air suspension.

Those spacing bands are why trailer bogie geometry is not a styling decision. Move the axles closer together and the legal capacity of the group falls, whatever the tyres are rated at.

Why the axle number bites before the gross number

The gross figure is an arithmetic total. The axle figures describe where the load actually is, and nothing about the gross reading tells you that.

On a semi-trailer combination the split is set by three things: the fifth-wheel position on the tractor, the bogie position on the trailer, and how the cargo was placed along the deck. Load a trailer heavy at the front and the tractor’s drive axle takes it. Load heavy at the rear and the trailer bogie does. Both cases can occur at 39 tonnes gross.

This is what the axle configuration notation is really describing. The first digit is the number of wheel positions, the second the number that are driven, and the figure after the slash the number of steered wheels — so a 6×2/4 is a three-axle vehicle with one driven axle and two axles that steer. A third axle on a tractor is added for load capacity or to stay inside statutory axle limits rather than for traction, and steering it reduces tyre scrub on a long wheelbase. The Scania S-series is offered in 4×2, 6×2, 6×2/2, 6×2/4, 6×4 and 6×6 for exactly this reason: the configurations are answers to different load-distribution problems, not trim levels. Where the third axle is liftable, it can be raised when running empty to cut rolling resistance and tyre wear and lowered when the load needs the capacity — a weight-distribution device first and a fuel-saving one second.

The manufacturer’s rating is a second, separate ceiling

Legal limits set what you may run. The manufacturer’s plated combination weight sets what the driveline is approved for. Both apply, and they are not the same conversation.

Makers rate GCW by driveline rather than by cab. Scania sets the permitted combination weight from the rear axle: 78 tonnes with a single driven single-reduction axle, 80 tonnes with hub reduction, and 210 tonnes with a tandem hub-reduction group. Volvo approves I-Shift variants of the FH from 44 tonnes up to 100 tonnes, with the crawler version rated to 325 tonnes. On the MAN TGX, the D38 6×4 tractor is plated at 44 tonnes where the 4×2 with the D26 is plated at 40. Anything above the legal ceiling runs on national permits, not on the plate alone.

National traffic is a different question entirely

Article 4 of the directive lets member states authorise vehicles in national transport that deviate from the weight points of Annex I. The 40-tonne figure is a rule about crossing borders, not a universal truth.

Sweden is the clearest case. Trafikverket classifies roads and bridges by bearing capacity: BK1 permits 64 tonnes gross, BK4 permits 74 tonnes, BK2 51.4 tonnes and BK3 37.5 tonnes — with the weight actually achievable still depending on the vehicle’s axle spacing and axle loads. The same tractor is a 40-tonne vehicle on an international run and a 64- or 74-tonne vehicle at home. If you buy used across a border, the plating and the axle specification tell you which market the truck was built for, and a Nordic-spec chassis is not automatically an advantage elsewhere.

The electric and gas exception

Annex I allows extra weight for cleaner powertrains: up to one tonne for an alternatively fuelled vehicle and up to two tonnes for a zero-emission one. Article 10b sets out the mechanism — the additional weight is established from the manufacturer’s documentation and recorded in the official proof the vehicle carries.

Two things about that allowance are routinely misread. It is compensation for the mass of the technology, not extra carrying capacity: the intent is to leave payload roughly where a diesel would have been. And it does not move the axle limits in point 3 of Annex I at all. A battery-electric tractor still has 11.5 tonnes available on its drive axle, and the axle is where the battery mass tends to land.

The practical effect shows up in what manufacturers publish. Mercedes-Benz rates the eActros 600 for a gross combination weight of up to 44 tonnes and quotes a payload of around 22 tonnes with a standard semi-trailer in the EU, noting that national law may permit more.

The rules are also moving. The Commission proposed a revision of the directive in July 2023; Parliament adopted a position in March 2024 seeking a four-tonne allowance for zero-emission trucks; and the Council agreed its position in December 2025 with allowances differentiated between five- and six-axle vehicles, plus up to 0.9 metres of extra length. Trilogue negotiations opened on 9 December 2025. Anyone specifying a zero-emission tractor on a long lead time is buying against a target that has not stopped moving.

Specify backwards from the axle

The useful habit is to work backwards from the axle rather than forwards from the gross. Decide the heaviest realistic load case, decide where on the deck that load sits, then choose the axle configuration and fifth-wheel position that keep every axle inside its band at that load. Only then check that the gross figure works. A third axle bought for gross capacity that still puts 12 tonnes on the drive axle has solved nothing, and it has cost you tare weight to do it.