Search Results

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.

This paper describes an analysis of roof contacts in inverted impacts. The proven methodology of lumped mass modeling is used to evaluate the effect of a number of variables on neck loading. Several parameters were evaluated including roof strength, drop height, head clearance, restraint use and stiffness, roof padding and neck stiffness. In general, the simulation results agreed well with existing head first impact test data. However, interesting results were obtained when neck stiffness was varied to represent the difference between human-like and Hybrid III spring rates. Biomechanical data generally agrees, independent of test methodology, that the Hybrid III neck is at least 10 times as stiff as a cadaver neck. Using an approximation of the Hybrid III neck stiffness (5.25 KN/cm) generally resulted in initial neck loads exceeding “upper” human tolerance level of 6500 N.

This study examines in some detail 23 actual rear-impact cases dealing with front seat collapse and compares the findings with similar results from 23 Canadian cases. In addition, seat tests and car-to-car crash tests are utilized to examine the potential hazards and/or benefits of collapsing versus non-collapsing seat systems. Evaluation of the above 46 cases indicates that an extremely high rate of rearward ejection occurs to restrained front-seat occupants subjected to rear impact. The majority of those ejected experienced serious to fatal injuries, either from contact in the rear or outside of the vehicle, when seated in collapsing seats. These results are contrary to some earlier published data and, as such, recommendations are made which could help improve data collection methods so as to better evaluate the issues associated with rear-impact seat strength.