Rear-Seat Occupant Responses in NHTSA Rear Crash Tests

Paper #:
  • 2018-01-1330

Published:
  • 2018-04-03
Abstract:
Objective: This study analyzed FMVSS 301 rear impact tests with an instrumented rear-seat dummy. The test data and videos were downloaded from NHTSA and divided into three series based on the presence or absence of a rear head restraint, instrumentation and video coverage. Methods: NHTSA conducted 15 FMVSS 301 rear crash tests with an instrumented 50th Hybrid III dummy in the rear seat. The dummy was lap-shoulder belted. In series 2, there were 8 tests with 2003-2005 MY vehicles that had rear head restraints. In series 3, there were two tests with 2004-2005 MY vehicles that did not have rear head restraints. There was an onboard camera view of the rear occupant. In series 1, there were three repeat tests with the Jeep Liberty and two others, but no onboard camera view. The dummy responses were evaluated and compared to IARV. Results: In series 2, the rear impact resulted in 17.2 ± 1.7 mph delta V in vehicles with rear head restraints and 17.6 ± 1.5 mph in the two tests in series 3 without a rear head restraint. The upper neck extension moment averaged 37% ± 20% in series 2 with a head restraint and 45% ± 15% without. The lower neck extension moment averaged 47% ± 21% in series 2 with a head restraint and 82% ± 35% without. The head-to-torso extension angle was -23.0 ± 18.1 deg in series 2 with a head restraint and -63.7 ± 0.4 deg without. All but one of the biomechanical responses were below IARV. In four tests with head restraints, the dummy ramped up the seatback and the head interacted with the roof liner causing neck compression and extension on rebound. Based on the HRMD, the average height of the rear head restraints was 31.6” ± 1.3”. In series 1, the delta V was 15.2 ± 1.3 mph. The upper neck extension moment averaged 28% ± 10% and the lower neck extension moment was 56% ± 26% with a head restraint. The neck extension angle was -34.2 ± 10.7 deg. Conclusion: This study provides an overview of NHTSA rear crash tests with an instrumented rear-seat 50th Hybrid III dummy. We are unaware of any publication of the findings from the testing. In the tests, the dummy loaded the rear seatback, which was integrated into the rear structures of the vehicle or free standing. The dummy compressed the trim and the head loaded the head restraint or extended onto the package shelf when there wasn’t a head restraint. The biomechanical responses were generally low with respect to IARV and there was good control of occupant kinematics, except in four tests in vehicles with head restraints where the occupant ramped up the seatback and the head interacted with the roof on rebound. This resulted in neck compression and extension and may be a factor for mid-sized and taller occupants in rear seats with head restraints.
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