The Mechanism operates through a spool that tightly coils the seat belt webbing when it is not being pulled. When a sudden stop occurs, the retractor locks in place, thereby preventing excessive movement of the occupant, which significantly reduces the risk of injury. NHTSA has considered these questions and attempted http://pandora.nla.gov.au/external.html?link=https://www.ledteks.com/seatbelt-and-safety-belt-webbing