Interaction between multiple convertible child restraint systems and pediatric occupants in oblique impacts

To assess the interaction of multiple rearward-facing (RF) and forward-facing (FF) CRS restrained pediatric occupants on their kinetics in oblique impacts.

A Q3s and a Q1.5 ATD were restrained in 2 CRSs of varying widths-standard (503mm) and slim-fit (425mm)-in the 2 rear outboard seats of a 2023 compact sedan rigidized rear seat bench. A surrogate door structure was mounted at the left outboard location. The Q1.5 was seated in an RF configuration, and the Q3s was seated in RF or FF configurations across tests. The ATDs were restrained as follows: (1) both ATDs in standard CRSs and (2) both ATDs in slim-fit CRSs, switching between the outboard seats for a total of 8 conditions. The condition with the highest head kinetic metrics from these tests was reproduced in a ninth test with the rear seat's center armrest lowered between CRSs. The entire environment was subjected to an oblique impact at 60° using the FMVSS 213 impact pulse.

The Q3s' head contacted the nearby CRS shell when seated farside. When seated nearside, the Q3s' head contacted the surrogate door structure in 1 of 4 conditions. The Q1.5's head contacted the nearby CRS in 2 of 4 conditions when seated farside. The Q3s when seated RF had higher HIC15 and head 3ms clip acceleration (H_3ms), regardless of farside or nearside position. When seated farside, upper neck tensile force (F_z) for the Q3s in FF configuration (2,317.4 and 2,077.9 N) was higher than that in RF configuration (1,850.8 and 1,802.8 N). When seated nearside, the same in FF configuration (701.3 and 1,029.4 N) was lower than that in RF configuration (997.6 and 1,261.7 N). Repeating the condition with the highest head kinetic metrics (HIC15 = 1246; H_3ms = 114.4 g) but lowering the center armrest between the CRSs resulted in lower head kinetic metrics (HIC15 = 916, H_3ms = 93.5 g).

In most cases, the farside seated ATD's head contacted the nearside CRS shell, resulting in elevated injury metric numbers and higher loading in both CRS types. The nearside ATD did not experience detrimental effects of the interaction with the farside occupant and CRS.