How do you determine the maximum authorised combination mass of a vehicle combination consisting of a towing vehicle with rigid drawbar trailer?

In German traffic regulations, when determining the maximum authorised combination mass (Gesamtzuggewicht) for a vehicle combination with a towing vehicle and a rigid drawbar trailer, the key factor is the trailer’s maximum authorised mass minus the trailer’s vertical axle load. This difference is compared to the permissible vertical load of the towing vehicle’s coupling point. If the trailer’s vertical load exceeds the towing vehicle’s permissible vertical load, the maximum authorised combination mass must be limited accordingly to avoid overloading the towing vehicle’s coupling. This ensures safe distribution of weight and prevents damage or unsafe driving conditions. Therefore, the correct method focuses on the trailer's maximum authorised mass minus the vertical load only when the vertical load is greater than what the towing vehicle can safely carry on its coupling.