What is the meaning of a circular traffic sign with a red border, white background, and a black diagram of a vehicle wheel axle with a tonnage number (e.g., '7t') across the axle?

1. Restriction on Axle Load: prohibits any vehicle whose axle load exceeds the indicated tonnage from passing
2. Restriction on Gross Mass: prohibits vehicles whose total combined mass exceeds 7 tonnes
3. Wheelbase Limitation: indicates vehicles must have an axle spread of at least 7 meters
4. Tire Pressure Warning: indicates vehicles must maintain tire pressure of 7 bar