Comparison of High and Low Speed Rear-Impact Head and Neck Injury Risk Measures Related to Occupant Size and Vehicle Seat Strength Characteristics

Abstract

This study demonstrates the use of efficient inferred statistical “factorial methods” for scientifically evaluating, with a relatively few tests, the rear-impact occupant “head and neck injury risk” performance of 2 different types of vehicle front seats, with adjustable headrests, when various size occupants are subjected to high and low impact severities. The 2 seat types studied included the stronger “belt-integrated seat” (BIS) designs, with restraints attached and having strength levels beyond 14 kN, and the more common but weaker single recliner (SR) seats, without attached restraints and having only about 3.2 kN strength. Sled-body-buck systems and full vehicle to barrier tests were run with “matched pairs” of surrogates in the 2 seat types at speed changes of 12.5 to 50 kph. Three sizes of Hybrid-III adult surrogates (i.e. 52 kg small female, 80 kg average male, and an average male surrogate ballasted to about 110 kg) were used in the evaluations. Also, some tests were run with 6 year-old Hybrid-III child surrogates located behind the front seats due to interest in potential child injury from collapsing front seats. The 2-level factorial method, combined with a biomechanical ratio comparison and a “student-t” test evaluation, were used to compare safety performance of the 2 seat designs. The resulting data analysis indicates that, in the mid to high range of rear impact severity (i.e. 20 to 50 kph), the stronger BIS seat systems tend to provide greatly improved “head-neck” protection over the weaker SR type seats for both the front seated adult occupants and rear seated children. At the low range of impact severity (i.e. 12.5 to 19 kph) there was no significant statistical difference between either seat types, except that the headrests of both could be improved.