Car Safety for Children Aged 4-12 : real world evaluations of long-term injury outcome, head injury causation scenarios, misuse, and pre-crash maneuver kinematics
Child casualties in car crashes have decreased over the years. Nevertheless, occupant safety
in rear seats, especially for children 4-12 years old, needs further attention because motor
vehicle crashes remain the leading cause of death and long-term health consequences for
children. The aim of this thesis was to obtain comprehensive knowledge of real-life
situations for restrained, forward-facing, rear-seated children aged 4-12 years, in frontal car
crashes as a basis for vehicle safety improvements to reduce long-term health consequences.
The thesis is comprised of four studies based on child-specific data from Sweden and the
US. Study I was based on injury data from insurance claim files, covering 2619 injured
children in Sweden. Study II was an experimental study of restraint misuse, including 130
Swedish children. Study III analyzed crash data included 27 cases from two US databases, to
determine injury causation scenarios. Study IV was a driving study of how pre-crash
maneuvers affect child occupant kinematics with 16 children included.
The results of Study I emphasized the importance of looking beyond acute, severe injuries
and also examine injuries (regardless of initial injury severity) resulting in permanent
medical impairment. The vast majority of injuries with the higher degree of permanent
medical impairment were severe injuries to the head. The most frequent injuries leading to
permanent medical impairment were minor injuries to the neck and head. To reduce the risk
of head injuries among children in car crashes, a fundamental step is to ensure that vehicle
restraint systems are adapted to the child, physically and behaviorally, and that the child is
properly restrained. An experimental study (Study II) of children using integrated booster
cushions compared to aftermarket belt positioning booster cushions, showed that misuse
related to buckling up, a problem for decades, can be reduced to a minimum by the design of
an integrated booster cushion. Minimizing misuse will lead to increases in proper positioning
of the restraint on the child and may translate to reductions in head injury risk. Therefore, car
manufacturers should focus on integrated booster cushions, preferably as standard
equipment.
Even with proper use, however, restrained children in rear seats sustained head injuries in
frontal impacts by impacting their heads on the side interior and on the seat back in front of
them. Oblique impacts and pre-crash steering maneuvers contributed to both these injurycausation
scenarios (Study III). Therefore, pre-crash steering maneuvers were further
explored in a driving study and it was confirmed that these common pre-crash maneuvers
can result in an unstable restraint situation that may potentially compromise rear occupant
safety in the event of a crash (Study IV).
In conclusion, the primary recommendation as a result of this research is to protect the head
and neck of child occupants from both minor and severe injuries, since all severity levels of
injuries may result in long-term consequences. Frontal impacts, including oblique impacts or
maneuvers prior to impact, need to be addressed to develop “tolerant” restraint systems.
Furthermore, it is recommendable to design and use vehicle-built-in restraint systems to
improve crash safety among children, by facilitating proper use of the restraint and
placement on the child, as has been previously done for front-seated adults. To incentivize
vehicle manufacturers to accelerate the implementation of child safety improvements within
their vehicles, an assessment of child safety for 4-12-year-old children should be included in
consumer rating programs and legal requirements