Vehicle weights explained

The different vehicle categories on your driving licence tell you what type of vehicle you are permitted to drive and can be dependent on your age. These categories are set by the weight of the vehicle.

Unladen weight

The unladen weight of any vehicle is the vehicle's own weight when not carrying any goods or burden. This is:

inclusive of the body and all parts which are necessary or usually used with the vehicle or trailer when working on a road exclusive of fuel and, in the case of an electrically powered vehicle, the batteries

Maximum authorised mass

The term maximum authorised mass (MAM), used in the context of driving licences, is the maximum weight of a vehicle or trailer including the maximum load that can be carried safely while used on the road. This is also known as gross vehicle weight (GVW) or permissible maximum weight.

It will be listed in the owner's manual and is normally shown on a plate or sticker fitted to the vehicle. The plate or sticker may also show a gross train weight (GTW).


If a vehicle is unlikely to be used at its potential maximum weight, it may be down-plated, so that a lower weight is specified on the plate. The manufacturer should be contacted, and a replacement plate sought to reflect the new weights.

Maximum weights

The maximum weights at which vehicles, trailers and articulated combinations can be used are marked on the vehicle's plate or can be found in the owner's manual.

On some vehicles the maximum weights may also be listed on the vehicle registration certificate V5C(NI). If in any doubt the vehicle or trailer manufacturer should be contacted.

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