Slidable seatbelt assembly for a wheelchair

An assembly comprising:

• a vehicle roof and a vehicle floor spaced from the vehicle roof;
• a seatbelt assembly slidably supported by the vehicle roof and the vehicle floor, the seatbelt assembly being slidable along the vehicle roof and the vehicle floor along a vehicle-longitudinal axis;
• the seatbelt assembly having a seatbelt webbing elongated in a direction from the vehicle roof to the vehicle floor;
• a seatbelt buckle slidably supported by the vehicle floor, the seatbelt buckle being slidable relative to the vehicle floor along the vehicle-longitudinal axis;
• and
• a computer including a processor and a memory storing instructions executable by the processor to:
• identify a position of a wheelchair along the vehicle-longitudinal axis;
• slide the seatbelt assembly along the vehicle-longitudinal axis to a position corresponding to the position of the wheelchair;
• and
• slide the seatbelt buckle along the vehicle-longitudinal axis to the position corresponding to the position of the seatbelt assembly.