A pretensioning lapbelt apparatus where the pretensioning of the lapbelt is performed by the rapid inflation of an airbag that is integral to the lapbelt itself. The design of the airbag, including the attachment locations of the ends of the webbing are chosen such that, upon inflation of the airbag, the free end of the webbing—the end of the webbing that is passed through the cinching latch—is pulled taught, thereby reducing the effective length of the lapbelt. The anchor is designed to be a cinching anchor such that once the airbag deploys and pulls the webbing through the anchor (thereby pretensioning the lapbelt) a sliding pin in the anchor “cinches” the webbing, effectively locking the webbing in the pretensioned state.