You are driving a vehicle combination comprising a motor vehicle and trailer, and you want to enter a road that has this signpost. What does the reference to “5.5 t” mean?

This sign indicates a weight limit for vehicles on the road. The "5.5 t" refers specifically to the maximum allowed actual mass of each individual vehicle, not the total combined weight of a vehicle and trailer or just the towing vehicle's authorized mass.

In the case of a vehicle combination (motor vehicle plus trailer), each part is considered separately. Both the motor vehicle and the trailer individually must not exceed 5.5 tonnes actual weight to enter this road. This ensures roads with weight restrictions are protected from damage caused by heavy vehicles.

Understanding this helps you recognize that weight limits on traffic signs apply per vehicle unit, not necessarily to the whole combination, so you must check the actual mass of each part when driving with trailers.