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 rein place, thereby preventing excessive movement of the occupant, which significantly reduces the risk of injury. NHTSA has considered the effects of this https://vuf.minagricultura.gov.co/Lists/Informacin%20Servicios%20Web/DispForm.aspx?ID=10574383