Effect of load limiting the shoulder-belt on right-front passenger kinematics in oblique-offset and NCAP frontal crash tests.

Objective: The effect of shoulder-belt load-limiting was evaluated on right-front passenger kinematics in 90 km/h oblique OMDB (offset moving deformable barrier) impacts and compared to kinematics in 56 km/h NCAP crash tests. The study focused on the influence of webbing pulling out of the retractor increasing forward excursion of the upper torso and head.

Methods: 18 OMDB crash tests were conducted by NHTSA at 90 km/h. The barrier was aligned at a 15 deg angle to the left (345 deg PDOF) with 35% overlap of the struck vehicle. The kinematics and biomechanical responses of the 50^th THOR passenger dummy were analyzed. The tests included 3 onboard video cameras covering the front occupants. The lap and shoulder belt loads were measured and displacement of the shoulder belt was available for most tests. The responses were compared to those in 11 NCAP frontal impacts at 56 km/h with a 5^th Hybrid III passenger.

Results: The delta V was 62.6 ± 2.8 km/h in the passenger car OMDB tests. The pretensioners and airbags deployed by 40 ms. The pretensioner pulled in -62 ± 29 mm of webbing at 13-15 m/s. With the retractor locked, belt loads increased as the passenger moved forward and inboard. The load-limiter paid out 280 ± 67 mm of shoulder belt webbing at 6-11 m/s and peak load of 4,170 ± 557 N. The shoulder belt slipped off the shoulder at 97 ± 10 ms. By 120 ms, the left shoulder impacted the center of the instrument panel and the head either impacted the panel or perched on the left edge of the airbag with the head rotated 80-135 deg about the z-axis (eyes right). There was 187.3 ± 37.4 mm of loose webbing after the test. Similar dummy responses were seen in the SUV and truck tests. In contrast, the passenger kinematics were centered on the airbag in NCAP tests without impact on the interior.

Conclusions: Excursion of the upper torso with the load-limiting shoulder belt enabled the belt to slip off the right shoulder in ODMB tests. The passenger flexed forward around the lap belt with impact on the center of the instrument panel. The upper torso lacked sufficient restraint with the level of load limiting in the tests. The belts were loose after pretensioning and load-limiting reducing the restraint effectiveness if there were a second or third impact or rollover in the collision sequence.