When may a bus driver drive along the hard shoulder (Pannenstreifen) of an Austrian motorway?

1. Never, apart from road service, road supervision and breakdown vehicles, the cases covered by StVO § 44d, accelerating to rejoin moving traffic, forming an emergency corridor, and where signs or markings allow it
2. Whenever the bus is running behind its published timetable
3. Whenever traffic in the running lanes is moving more slowly than the bus
4. At any time, provided the hazard warning lights are switched on