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The Federal Motor Vehicle Safety Standards (FMVSS) require rear seat, lap/shoulder belts to “fit” Hybrid III dummies ranging in size from a 6 year old child (H3-6C) to a 95th-percentile-male (H3-95M). No dynamic performance FMVSS, however, exist for rear seat belt systems. Variations in the three-dimensional “fit” of the same lap-shoulder belt positioned around these extreme dummy sizes suggest a possible difference in performance. The purpose of this study was to assess the performance of two production lap-shoulder belt designs in a large SUV buck on a rebound sled using instrumented H3-6C, 5th-percentile-female (H3-5F) and H3-95M dummies. Sled velocities were approximately 35 kph. Test instrumentation included: lap and shoulder belt load transducers, triaxial accelerometers at the center of gravity of the head, triaxial accelerometers and a deflection gauge in the chest, and six-axis force (and moment) transducers in the neck of the dummy.

Catastrophic head and spinal injuries have been reported to older children, properly restrained in the back seats of motor vehicles. The interaction of small stature occupants in contemporary, rear restraint systems has not yet been reported in controlled frontal oblique sled test conditions. Such data is fundamental to understanding potential mechanisms of injuries and effective countermeasures. The purpose of this study was three fold: (1) to conduct a series of controlled sled tests to determine the critical angle at which torso roll-out from the shoulder belt occurs in 6 year old Hybrid III (H3-6C) and 5th percentile female Hybrid III (H3-5F) dummies, (2) to compare dummy injury measures to the standard Injury Assessment Reference Values (IARVs) as a function of impact angle, and (3) to assess the influence of belt pretensioners and anchorage geometry as countermeasures to submarining and torso rollout dummy kinematics.

A gap in protection appears to exist for older children who have outgrown booster seats and are placed in some adult, 3-point belts with fixed shoulder belt anchorage points. Boys on average do not reach the 50th percentile adult, male seated height until age 15 ½ and the average girl never reaches this height. The published minimum seated height and weight thresholds for use of three-point belts alone are inconsistent with the official recommendations by The National Transportation Safety Board and the majority of state seat belt laws. A shoulder belt with a fixed upper anchorage, which is typical in the rear occupant space, may create torso belt routing that can allow rollout from the shoulder belt in frontal oblique collisions. A belt trajectory that passes across the neck of an older child may create an artificial fulcrum in the cervical spine resulting in quadriplegia. Excessive webbing lengths can promote child occupant excursion, rebound and injurious head contact.

The purpose of this research was to present and analyze a previously unreported mechanism of injury within the automotive crash environment - spinal burst or compression fractures due to a vertical force component. Spinal burst fractures are comminuted fractures of the vertebral body which are often associated with retropulsed bone fragments into the spinal. Compression fractures are less traumatic fractures of the vertebral body with minimal comminution. Both fracture types can have varying degrees of neurologic deficit. The mechanism of injury is hypothesized to be a high energy compressive load along the axis of the spine initiated through the buttocks and pelvis or through torso augmentation (inertial loading of the lumbar spine by the torso). Four crashes are presented as evidence of this injury mechanism within the automotive crash environment: two in the United States and two in Germany.

Automotive collision data from the National Accident Sampling System database (compiled by the National Highway Traffic Safety Administration) was analyzed in regard to occupants who sustained major pelvic injuries during 1980-1992. These injuries included pelvic fracture, pelvic dislocation, pelvic separation, pelvic crush, and pelvic fracture/dislocation. All collisions analyzed were required to have a computed change in velocity during the collision, as well as data concerning injuries sustained by the occupants. The purpose of this research was to retrospectively analyze motor vehicle crash data to establish incidence of major pelvic injuries within automotive collisions. From the study, 1.8% of all collisions evaluated resulted in major pelvic injuries. Twenty-two percent of all crashes were side impact collisions and 8% of these side impact collisions resulted in occupants sustaining major pelvic injuries.