Are agricultural tractors and Category F vehicles permitted to drive on Austrian motorways (Autobahn) or expressways (Autostraße)?

1. Yes, any tractor can use the motorway if it stays on the hard shoulder
2. Yes, provided the tractor turns on its hazard warning flashers
3. No, because StVO § 46 opens the motorway only to motor vehicles with a design speed of at least 60 km/h that are also allowed to exceed that speed
4. Yes, but only during nighttime hours between 22:00 and 05:00