Child Passenger Kinematics in Emergency Manoeuvres

Licentiatavhandling, 2012

ABSTRACT In motor vehicle impacts, a child’s head is generally the most frequently injured body region, irrespective of impact direction. Head to front seat back impact has been identified as a predominant cause of injury for rear seated, seat belt restrained children, aged 3 – 13, who sustained AIS2+ head injuries in frontal impacts. Previous research highlights vehicle manoeuvres prior to impact as possible contributing factors. Test tools to simulate occupant kinematics during emergency braking and steering manoeuvres would be valuable when investigating different scenarios and restraint systems. This thesis investigates children’s and different Anthropomorphic Test Devices’ (ATDs’) motion during emergency braking and steering manoeuvres in a passenger vehicle. The kinematic responses of child volunteers during the emergency manoeuvres in different restraint configurations were compared and discussed, and the current child ATDs from the Q-family and the Hybrid III (HIII) family were evaluated with respect to child occupants. The forward displacement was within the same range during the braking manoeuvres for all tested children, regardless of size and restraint system. All ATDs displayed less forward displacement and head rotation than the child volunteers; the HIII 6 year old on a booster cushion was closest to representing the kinematics of a child of similar age/size in this set-up. Maximum excursion was dependent on the initial seated posture and shoulder belt position on the shoulder. Boosters with a backrest influenced the initial seated posture and thus resulted in the head position being more forward during maximum excursion. For the steering manoeuvres, the Q ATDs were closer regarding mean values compared to the children, however due to the large variety in lateral displacements of the children, the child performance range covers both the dummy families for the evaluated sizes of 6 and 10 year old ATDs in this set-up. The braking and steering manoeuvres with child volunteers and ATDs carried out in this thesis provide novel and unique knowledge of possible pre-crash postures of children and currently available ATDs across a variety of restraint systems in vehicle emergency manoeuvres. The test methods and methods of analysis were repeatable and the results offer input to safety system development, ATD design as well as test method development. Appropriate initial shoulder belt position is important during steering and braking manoeuvres. For real world protection, it is important to take into account the growing child, focusing on and understanding such aspects as initial seated posture, i.e., head position, shoulder belt position and how the child is restrained by the seat belt, as well as the booster design. KEYWORDS: methods, pre-crash, braking, steering, child volunteers, child restraint systems, child ATD