National Trailer & Towing Association
Promoting Safe and Legal Towing

Glossary of terms used in this guide

Unladen Weight (UW)

The weight of the trailer (or towing vehicle) less removable optional equipment and load

Gross Weight

The total weight of the trailer (or towing vehicle) and load Gross Vehicle Weight (GVW) or Gross Weight Mass (GWM) The total weight of the towing vehicle and its load

Maximum Gross Weight (MGW)

The maximum figure set by the manufacturer for the gross weight. This will normally be the technically permissible maximum based on the carrying capacity of the tyres, axles, coupling, suspension and chassis but may have been adjusted downwards for commercial reasons

Technically Permissible Maximum Weight

The technically permissible maximum based on the capacity of the tyres, axles, coupling, suspension and chassis

Maximum Authorised Mass (MAM)

As maximum gross weight above. The latest EC term as used in the Driver Licensing Regulations

Gross Train Weight (GTW )

The maximum allowable combined weight (combined MAM) of the towing vehicle and trailer as set by the towing vehicle manufacturer

Payload:

The difference between the gross weight of the trailer and its unladen weight, i.e. The load carrying capacity

Kerb Weight/Kerbside Weight

The weight of the towing vehicle (without payload), including all fluids required for operation (95/48/EEC: Vehicle, 90% full tank, 68kg driver and 7kg luggage.)

Vertical Static Load/Nose Load

The weight imposed on the towball or eye by the trailer coupling

Over-run Braking System:

A trailer braking system operated by the action of the trailer bearing on the towing vehicle under deceleration

Power Operated Braking System

A trailer braking system which is operated directly by the Action of the foot brake on the towing vehicle

Wheel Track

Horizontal distance between the centre lines of the wheels across the width of the vehicle or trailer

Wheel Base

Horizontal distance between the centre lines of the wheels of multi-axle vehicles or trailers along the length of the vehicle or trailer

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