If you drive a tractor, in which of the following cases can you enter the road once you go past this sign?

The D-9 'motorway' sign shown indicates the start of a motorway. In accordance with regulations, slow-moving vehicles, which include agricultural tractors, are not permitted on the motorway. However, the law permits an exception for vehicles carrying out cleaning, repair or modernisation work on the road; therefore, in such a situation, entry would be permitted.