title: Rear seat occupant safety: an investigation of a progressive force-limiting, pretensioning 3-point belt system using adult PMHS in frontal sled tests.
abstract: Rear seat adult occupant protection is receiving increased attention from the automotive safety community. Recent anthropomorphic test device (ATD) studies have suggested that it may be possible to improve kinematics and reduce injuries to rear seat occupants in frontal collisions by incorporating shoulder-belt force-limiting and pretensioning (FL+PT) technologies into rear seat 3-point belt restraints. This study seeks to further investigate the feasibility and potential kinematic benefits of a FL+PT rear seat, 3-point belt restraint system in a series of 48 kmh frontal impact sled tests (20 g, 80 ms sled acceleration pulse) performed with post mortem human surrogates (PMHS). Three PMHS were tested with a 3-point belt restraint with a progressive (two-stage) force limiting and pretensioing retractor in a sled buck representing the rear seat occupant environment of a 2004 mid-sized sedan. Instrumentation included belt tension load cells, accelerometers on the head and at multiple locations on the spine, and chestbands to measure the chest deformation contours in the transverse plane. The kinematics of the subjects were quantified using off-board, high-speed video. The results of these tests were then compared to matched PMHS tests, published in 2008, performed in the same environment with a standard (not-force limited, not pretensioning) 3-point belt restraint. The FL+PT restraint system resulted in significant (p<0.05) decreases in peak shoulder belt tension (average +/- standard deviation: 4.4 +/- 0.13 kN with the FL+PT belt, 7.8 +/- 0. 6 kN with the standard belt) and 3 ms-resultant, mid-spine acceleration (FL+PT: 34 +/- 3.8 g; standard belt: 44 +/- 1.4 g). The FL+PT tests also produced more forward torso rotation caused by decreased forward excursion of the pelvis and increased payout out of the shoulder belt by the force-limiter. These results support the previous ATD studies that suggest that it may be possible to improve the kinematics of rear seat occupants in this type of collision using a 3-point belt system with a shoulder belt retractor equipped with a two-stage force-limiter and pretensioner.
authors.affiliation: University of Virginia, Center for Applied Biomechanics, USA. jlf3m@virginia.edu
authors.forename: Jason
authors.initials: J
authors.lastname: Forman
authors.forename: Francisco
authors.initials: F
authors.lastname: Lopez-Valdes
authors.forename: David
authors.initials: D
authors.lastname: Lessley
authors.forename: Matthew
authors.initials: M
authors.lastname: Kindig
authors.forename: Richard
authors.initials: R
authors.lastname: Kent
authors.forename: Stephen
authors.initials: S
authors.lastname: Ridella
authors.forename: Ola
authors.initials: O
authors.lastname: Bostrom
mesh_terms: D000054:Acceleration / Q000009:adverse effects*; D000063:Accidents, Traffic; D000368:Aged; D002102:Cadaver; D003198:Computer Simulation; D019544:Equipment Failure Analysis; D050723:Fractures, Bone / Q000209:etiology* / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D009068:Movement; D012622:Seat Belts / Q000009:adverse effects*; D013124:Spinal Injuries / Q000209:etiology* / Q000503:physiopathology*; D013314:Stress, Mechanical; D013898:Thoracic Injuries / Q000209:etiology* / Q000503:physiopathology*; D013909:Thorax / Q000503:physiopathology