What is the status of single-line pneumatic trailer braking systems (Einleitungs-Druckluftbremsanlage) under modern Austrian vehicle regulations?

1. They may still be fitted to new trailers up to 3,500 kg
2. They are permitted on new vehicles provided a second air reservoir is fitted
3. They must be fitted in addition to a dual-line system on all agricultural trailers
4. They are legacy systems limited to existing older machinery at 25 km/h and cannot be type-approved for newly registered tractor combinations