The effect of reclined seat-back angles on the LODC with and without a belt-positioning booster during far-side lateral-oblique impacts.

Objective: In frontal crashes belt-positioning boosters (BPB) may prevent submarining when the seatback is reclined. It is unclear if the BPB can also mitigate injuries in far-side lateral-oblique crashes in reclined conditions, where current restraints are less effective in reducing lateral excursion. This study aimed to understand reclined child injury risk during lateral-oblique impacts, with and without a booster seat, by using the Large Omni-Directional Child (LODC) test device.

Methods: The LODC was tested in nine lateral-oblique impact (80° from frontal) sled tests (target 31.3 km/h, duration 58 ms maximum, peak acceleration 21 g). Three seatback angles (25°, 45°, and 60°) with and without the BPB were compared on a production passenger seat with an integrated seatbelt. The LODC moved toward the buckle side during the far-side lateral-oblique impact. Abdominal pressure (left and right), seatbelt loads, anterior superioriliac spine (ASIS) forces, and pelvis lateral rotation were examined. The LODC head and knee excursions were extracted from a 3D-motion capture system.

Results: In the reclined noBPB condition, peak abdominal pressures on the buckle side reached up to 186 kPa and the ASIS forces demonstrated an early (∼ 50 ms) peak and a subsequent drop in the reclined noBPB conditions, suggesting that the belt slid into the abdomen.With the BPB, peak pelvis lateral rotation was greater than in the noBPB conditions but decreased with increasing reclined seatback angles (BPB: 31° to 36.5° vs no-BPB: -5° to -4.6°). Peak lap belt forces were greater in the reclined noBPB conditions (4.8-4.9 kN) compared to all conditions with the BPB (2.9-3.2 kN).The greatest lateral head excursion was observed in the BPB 25° condition (895 mm) and the lowest in the noBPB 45° condition (748 mm).

Conclusions: The BPB may prevent the lap belt intrusion into the abdomen in reclined configurations in far side lateral-oblique impacts. The greater pelvis lateral rotation and head displacement with the BPB may lead to contact with other rear-seated occupants and/or vehicle structures, although motion decreased with the BPB as the reclined seatback angle increased. This suggests that reclined seats may help reduce BPB-seated children's lateral excursion in far-side lateral-oblique impacts.