Which vehicles are prohibited from using a road sign-posted like this?

This traffic sign prohibits vehicles with an actual axle load exceeding 2 tons from using the road. In German traffic rules, the key factor here is the "actual" axle weight, meaning the real load on the axle at the time of driving.

It does not refer to the permissible or maximum axle weight allowed by vehicle specifications, but the current load being carried by the axle. Vehicles that actually exceed 2 tons per axle cannot proceed past this sign to protect the road from damage due to heavy axle loads.

Understanding this distinction helps you recognize that even if a vehicle is authorized for a higher axle load, what matters here is the actual weight during operation. Therefore, answer 1 is correct, as it specifies vehicles with an actual axle weight exceeding 2 tons.