When is a 10 km/h speed rating plate (10er-Tafel) mandatory on agricultural equipment in Austria?

1. On all modern high-speed tractors driving on motorways
2. On specific low-speed machinery, solid rubber-tyred vehicles, certain unregistered implements, or special heavy transport rigs
3. On any trailer that is registered for traffic and rated at 40 km/h
4. On passenger cars towing a boat trailer