Which traffic sign refers to the actual mass?

Your answer is correct. Sign No. 1 indicates a weight limit referring to the actual (gross) mass of the vehicle, meaning vehicles exceeding 5.5 tons are not allowed to pass. This sign restricts traffic based on the total weight of the vehicle including its load at the time of driving.

Sign No. 2, on the other hand, is a general prohibition of trucks and does not specify a weight limit or refer to the actual mass. It simply prohibits trucks from entering.

In summary, when a traffic sign refers to the "actual mass," it shows a specific weight limit like in No. 1, indicating the maximum allowed gross weight of the vehicle. This is important to prevent damage to roads or bridges and ensure safety.