<div class="htmlview paragraph">Contemporary production emergency locking seatbelt retractors (ELRs) have been proven very effective in the crash environment for which they have been primarily designed and most adequately tested, that is, in the full frontal crash mode. However, researchers have documented spool out during offset, angled, override, underride, and rollover crashes where seatbelt retractors are subject to acceleration pulses in varying directions, including the vertical plane. Occupant motions during these real world accident modes may also impart loads into the belts and belt hardware (webbing and buckle assemblies) that may not be immediately apparent in the frontal barrier test mode. Numerous laboratory studies have demonstrated that the inertial sensor can be held in the neutral position when an overriding opposing force is applied to the retractor, resulting in webbing spool out. Various ELR designs include ball and cage sensors, pendulum, and disk systems.</div> <div class="htmlview paragraph">These authors have mounted various typical production ELR type retractors to testing apparatus capable of applying acceleration pulses in various directions. These experiments demonstrate, via high-speed video, the potential for belt spool out with an opposing, overriding force. Moreover, these experiments, when considered with respect to real world out-of-plane crashes, explain the significant belt spool out documented in the field.</div>