Search Results

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. The emergency-locking portions of seat belt retractors are critical components that engage as a result of vehicle deceleration and lock the retractor as webbing is withdrawn during the onset of occupant loading. The field performance of emergency-locking retractors (ELRs) is commonly called into question. Recent studies have raised concerns about the effectiveness of retractor locking mechanisms in multi-planar collisions, including rollovers. Investigators of vehicle crashes would benefit from samples of diagnostic physical evidence which could be used to assist in distinguishing between an unrestrained occupant, a properly restrained occupant and a restrained occupant where the ELR mechanism was disabled in a crash environment and allowed webbing to “spool-out”.

Rollover crash and accident studies identify significant roof-to-ground impacts adjacent to the vehicle occupant as a potential cause of severe injuries. It is not possible with existing dynamic rollover test methods to specifically repeat or recreate a particular roof-to-ground impact in a controlled fashion. Variations associated with tire-to-dolly, tire/wheel-to-ground, and vehicle-to-ground interactions early in current rollover test methods tend to produce unpredictable and unrepeatable roof-to-ground impacts later in the test. A new test device now enables researchers to bypass the uncertainty of these first ground interactions by beginning each test with the desired roof-to-ground impact conditions as a test input. The new rollover test method releases a rotating vehicle onto the ground from the back of a moving semi-trailer.

In rollovers, belted occupants sustain a lower fatality rate compared to unbelted occupants primarily due to lower risk of partial or full ejection. However, seat belt and occupant compartment designs found in most current vehicles do not prevent head contact with the vehicle interior during a rollover because of occupant torso and head excursion that result from the rollover dynamics. An experimental study was conducted to simulate the airborne phase of a rollover. The goals of this study were to: 1) quantify the effect of restraint anchor locations and belt component designs in reducing head excursion, and 2) to better correlate the response between humans and an Anthropomorphic Test Device (ATD) during the high angular roll rate of the airborne phase of a rollover. A Head Excursion Test Device was designed to rotate a restrained occupant about an axis to approximate the inertial loading experienced during the airborne phase of a rollover.

Laboratory testing measured the response of a 1984 Chevrolet S-10 Blazer seatbelt buckle to impact on the back of the buckle. The peak acceleration, pulse duration and webbing tension were recorded to map the unique circumstances necessary to inertially unlatch the buckle. The conditions necessary to inertially unlatch the buckle in the laboratory were compared with the measured buckle responses in fifteen sled tests and six rollover crash tests using anthropomorphic dummies. All of the crash tested buckles remained latched and all had dynamic responses well below those required to produce inertial unlatching. Dummy hip areas were measured to be significantly stiffer than humans. Buckle accelerations measured in the “parlor trick” of intentionally striking the hip with a buckle are not representative of crash conditions.