Injury Mechanisms in Rear Seated Children Aged 9-17 Years and the Implications for Assessing Rear Seat Protection in Crash Tests

This study examines injury mechanisms among rear seated restrained child occupants between 9 and 17 years of age using in-depth crash investigation. It was intended to determine whether current crash assessment protocols could be improved to better represent non-booster seat using children in the rear seat of cars. Rear seat occupants aged older than 9 years were recruited from 6 major New South Wales (NSW) trauma and paediatric hospitals. A detailed review of injury mechanisms, crash and restraint factors and injury outcome was conducted. The case series consists of 20 occupants aged 9-17 years, 14 were in frontal impacts, 5 in side impact and 1 rear impact. Three occupants used a lap only belt and the remainder used lap sash belts. Thoracolumbar spine, chest and abdominal injuries were the most common injuries in frontal crashes. Head and pelvic injuries featured in side impacts. A neck injury was present in a rear impact case. Thoracolumbar spine injuries were associated with lumbar flexion in combination with submarining; and with axial compression, caused by excessive chest loads. Abdominal and chest injury was associated with belt loading. In side impact, contact with intruding structures was the primary mechanism of injury. Although this case series is not representative of all rear seated children in crashes, the high proportion of thoracolumbar spine and abdominal injuries observed indicates a need for greater focus on preventing these injuries in older children using the rear seat. During vehicle crash testing, the inclusion of lumbar spine injury measures in dummies would allow for a greater understanding of the effectiveness of safety technologies in the rear seat, as would validated measures of abdominal injury. Dummy measurements in front seat assessment focus on head, neck, chest and femur loads. While protecting these regions is important for all occupants, this study has demonstrated other body regions that require assessment when addressing rear seat occupant protection. Further the majority of injuries in this case series would not be captured using existing front seat dummy protocols. The results indicate different injury sources for rear occupants than reported for front occupants. Simply extending existing front seat assessment protocols to the rear seat may not adequately assess injury risk for older children in the rear seat.