What does a circular sign with a red border showing a black axle with two wheels and the text '8t' above it mean?

1. A maximum speed limit of 80 km/h for heavy vehicles
2. An axle load limit of 8 tonnes; vehicles exceeding this limit on any axle cannot pass
3. A vehicle total weight limit of 8 tonnes
4. A restriction limiting the road to vehicles with at least 8 axles