Rear passenger restraint in frontal NCAP tests compared to the right-front passenger.

Objective: This study compared kinematic and biomechanic responses of the 5^th female Hybrid III in the right-rear and right-front passenger seats in frontal NCAP tests with 2015-16 MY vehicles. It focused on the lap-shoulder belt restraint of the rear passenger.

Methods: Eleven frontal NCAP tests were conducted by NHTSA at 56 km/h with a lap-shoulder belted 5^th Hybrid III dummy in the right-rear and right-front seats. The right-front passenger had pretensioning and load limiting belts and advanced airbags with inflatable knee bolster. The rear passenger had seatbelts without pretensioning or load limiting. The kinematic and biomechanical responses of the 5^th Hybrid III dummy in the rear and front were analyzed. The tests included onboard video cameras covering the rear and front passenger. Lap and shoulder belt loads were measured. The responses were compared for the two seating positions and restraint systems.

Results: Only one of 11 vehicles had favorable restraint of the right-rear passenger. All vehicles passed criteria for the right-front passenger. The right-rear passenger HIC₁₅ was 888 ± 314 (779 IARV) significantly higher than 242 ± 72 in the right-front passenger (t = 6.36, p < 0.001). The right rear Nij was 1.16 ± 0.19 (1.00 IARV) significantly higher than 0.46 ± 0.11 in the right-front (t = 9.18, p < 0.001) and the rear chest deflection was 46.1 ± 9.8 mm (42 mm IARV) significantly higher than 20.8 ± 5.6 mm in the right-front (t = 7.12, p < 0.001). The shoulder belt load was 8,771 ± 2,088 N on the right-rear passenger significantly higher than 3,564 ± 911 N on the right-front (t = 7.28, p < 0.001). Three of the 11 crash tests involved submarining by the right-rear passenger at 76.0 ± 7.2 ms. Two tests with submarining involved the seatbelt buckle lifting by shoulder belt load pulling the lap belt onto the abdomen. One test involved compressing the front of the seat cushion with the H-point dropping, the pelvis rotating rearward and the lap belt sliding onto the abdomen.

Conclusions: Restraining loads on the rear passenger were significantly higher than on the right-front passenger in 2015-16 MY vehicle NCAP tests. The HIC₁₅ was 3.7-times higher in the rear passenger than the front. The Nij was 2.5-times higher and chest deflection was 2.2-times higher. The dummy responses were significantly higher in the rear seat compared to the front seat because of greater restraining loads, submarining and a hardware failure in NCAP tests. The lack of pretensioning, load limiting and airbags involved higher injury risks in the rear passenger compared to the right-front passenger.