The Influence of Body Mounted Shoulder Seat Belt Anchor (D-Ring) Displacement During Dynamic Vehicle-to-Ground Impacts

For more than 30 years, field research and laboratory testing have consistently demonstrated that properly wearing a seat belt dramatically reduces the risk of occupant death or serious injury in motor vehicle crashes. In severe rollover crashes, deformation to vehicle body structures can relocate body-mounted seat belt anchors altering seat belt geometry. In particular, roof pillar mounted shoulder belt anchors (“D-rings”) are subject to vertical and lateral deformation in the vehicle coordinate system. The ROllover Component test System (ROCS) test device was utilized to evaluate seat belt system performance in simulated severe rollover roof-to-ground impacts. A mechanical actuator was designed to dynamically relocate the D-ring assembly during a roof-to-ground impact event in an otherwise rigid test vehicle fixture. Anthropomorphic test device (ATD) kinematics and kinetics and seat belt tensions were compared between tests with and without D-ring relocation. Results indicate that the displacement of the shoulder belt anchor does not have a substantial effect on either ATD axial neck loads or the restraint provided by the seat belt system while limiting the vertical motion of the ATD during a single roof-to-ground impact.