What is the legal rule regarding passenger seatbelt usage on long-distance touring coaches (Class III / M3 Reisebusse) in Austria?

1. If seatbelts are fitted, all passengers aged 3 and older are legally required to buckle up, and the driver must inform passengers under KFG § 106
2. Seatbelts are completely optional for passengers and only mandatory for the driver
3. Only passengers sitting in the first row behind the driver must wear seatbelts
4. Seatbelts are only required when the coach travels on foreign motorways