KINEMATICS AND SHOULDER BELT ENGAGEMENT OF CHILDREN ON BELT-POSITIONING BOOSTERS DURING EVASIVE STEERING MANEUVERS

Objective: To increase the protection of child passengers in crashes preceded by evasive steering, understanding of how children interact with the seatbelt in such situations is essential. This study aims to quantify child kinematics and describe child-to-restraint interaction during evasive steering maneuvers. Methods: Eighteen child volunteers (aged 5-10) were seated on the rear seat of a passenger vehicle. A professional driver made repeatable sharp turns at 50 km/h. Children were restrained by the seatbelt on a booster cushion (BC) and on an integrated booster cushion (IBC). Kinematics of the nasion and upper sternum were analyzed with video tracking software and shoulder belt (SB) engagement and position were evaluated.Results: Children moved laterally inboard, and SB-to-body interaction was influenced by booster and stature. For shorter children, the SB was closer to the neck with more of the belt webbing in contact with the torso and a more curved belt paths on the IBC compared to the BC, where less of the SB was in contact with the torso and straight belt paths were observed throughout steering. Taller children generally had the SB initially mid-shoulder with more contact between the SB and torso, resulting in curved belt paths at initial and maximum displacement on both boosters. Children loaded the shoulder belt by axially rotating their torso into the SB more often on the IBC compared to BC. The SB generally stayed on the shoulder, with 89% of slip-off instances occurring for shorter children on the BC. Shorter children on the BC had the largest average inboard nasion displacement of 105 mm initially and 120 mm overall. Taller children on the BC had the lowest average inboard displacement of the nasion (85 mm initially, 100 mm overall). All children initially displaced on average between 65-75 mm inboard with their sternum and 90 mm overall. Conclusions: Initial SB position on the shoulder and torso differed with booster and stature, which influenced how children engaged with the seatbelt during steering. Children with less SB initially in contact with the torso moved laterally behind the belt, resulting in straighter SB paths and outboard motion of the SB on the shoulder (often ending far out or slipped-off). When more of the SB was initially in contact with the torso, children tended to engage the SB more, moving with the belt and causing the SB path to become more curved, resulting in less inboard head displacement and less outboard motion of the SB on the shoulder. Enhanced understanding of how evasive steering affects the kinematic response of children provides valuable data for protection of children in real world situations