What is the specific safety advantage of the 'Kraftknoten' integrated restraint interface (according to DIN 75078-2) on accessible wheelchairs transported in Austrian buses?

1. It allows the wheelchair to fold flat while the passenger remains seated
2. It provides standardized, crash-tested attachment points on the wheelchair frame that allow rapid docking of the 4-point tie-downs and correctly routes the passenger lap-and-diagonal seatbelt across the pelvis
3. It automatically inflates an airbag inside the bus entrance vestibule
4. It eliminates the requirement for the bus driver to verify passenger securement