The loaded mass of the trailer must not exceed the lesser of:
- Rated capacity of the towbar and tow coupling.
- Maximum towing capacity of the vehicle.
- Maximum carrying capacity of the trailer.
- Maximum rated carrying capacity of the tyres.
If the vehicle manufacturer has not speciﬁed the maximum towing mass, the maximum towing mass is:
- One and a half times the unladen mass of the towing vehicle, provided that the trailer is ﬁtted with brakes which are connected and in working order, or
- The unladen mass of the towing vehicle if the trailer does not require brakes.
Vehicles with a manufacturer’s gross combination mass (GCM) more than 4.5 tonne may tow in accordance with the above requirements.The GCM is the gross combination mass of the car and loaded trailer.