Supplemental Restraint Systems

Seatbelt Pre-Tensioner The pretensioner mechanism uses an explosive charge to drive a concealed piston when sensors detect the abrupt deceleration of an accident. The piston, in turn, rapidly drives the spool around which the fabric strap of a seatbelt is wrapped. That incredibly fast retraction of the belt fabric removes the slack from the belt instantly. This extra seatbelt "pre-" tension, moments prior to the full force of impact, pulls the bodies of the driver and passengers firmly into their seats. This positions them to receive the maximum protection benefit of the airbags. It also helps prevent submarining, that's when the momentum caused by the crash jerks a victim's body under his or her lap belt and sends it careening forwards.