When it comes to collisions, children are a special group with different injury tolerances than adults, and as such, require special safety considerations. According to Transport Canada, seven thousand children ages 0 to 12 are killed or injured every year as a result of a collision.[1]   While it is impossible to completely eliminate the risk of injury, selecting the appropriate child seat, correct seating location, and properly/firmly installing the seat can help reduce the risk of serious injury to little ones in collisions.

The biomechanics behind proper child seat selection

Compared to infants and children, the adult neck is more developed and therefore better able to withstand collision forces. Children’s lack of neck strength combined with their increased head size (relative to body size) increases the risk of spinal cord injury and leaves them at a serious disadvantage when it comes to their risk of injury in a collision. As a result, it is recommended that infants and young children be placed in a rear-facing seat to better support the child in the case of a collision. The reasoning behind this recommendation can be explained by examining the occupant kinematics (occupant motion) in the case of a frontal collision. When a child is secured in a forward-facing seat (see “Example A” in the illustration below), the child’s momentum during a frontal collision would cause them to move forward until restrained by their seatbelt. While their torso is restrained by the seatbelt, their head would continue to move forward, resulting in significant flexion of the neck which could lead to serious injury or even death in infants and young children. However, in the case of a frontal collision where a child is in a rear-facing seat (see “Example B” in the illustration below), their forward motion would be limited by the seat back of the child seat; they would compress into the seat back of the child seat, which provides support for the back, neck, and head. The rear-facing child seat eliminates the significant neck flexion observed in front-facing seats during frontal collisions, and it is for this reason that infants and young children should remain in a rear-facing seat as long as possible (until they weigh at least 20 lbs).

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When a child outgrows the height and weight recommendations of the rear-facing child seat they can graduate to a forward facing seat (weight between 20 and 40 lbs), and then eventually to a booster seat, and then adult seatbelt. Once old enough to wear an adult seatbelt, the child can benefit from additional safety features (pretensioner and load limiter) that removes slack in the seatbelt and helps to control the motion of the occupant while reducing the risk of injury in a collision. A timeline showing the child seat versus the weight and height recommendations according to the Ministry of Transportation is shown below.[2]

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child-seat-seal-canadaWhen selecting a car seat, it is worth noting that car seats sold in Canada also come with a label (see left) indicating that the seat complies with national standards and regulations, as well as an expiry or useful life date.

Where is the safest spot for the child’s car seat?

Firstly, a rear-facing child seat should never be installed in the front seat. This is a topic that received much attention when airbags first started coming into use in the 1990’s. The design of the rear-facing seat places the child seat and infants head in very close proximity to the passenger airbag which deploys at extremely high speeds (up to 320 km/h) and significantly increases their risk of injury. Newer vehicles now discern the weight of the occupant in the passenger seat and may automatically deactivate the passenger airbag. If a rear-facing child seat is positioned in the front seat, the airbag will contact the back of the child seat, forcing it rearward into the seatback of the front passenger seat. Studies have shown that the head accelerations experienced by infant dummies (100 to 200 g) exceed that tolerable by infants (~50 g) by a factor of 2 to 4.[3] In addition to injuries caused by the acceleration of the head (and brain), the infant will likely sustain injuries during a secondary collision with the passenger seat back (as shown below).

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However, it is not just infants that benefit from being positioned in the rear seat. While frontal airbags have been proven to be an excellent safety feature for adults, they have also been shown to dramatically increase child fatalities. Airbag exposure significantly increases the risk of death for children under 9 years of age and children positioned in the front seat are twice as likely to sustain serious injuries when compared to those positioned in the rear seat during a frontal collision.[4] [5] Hence why it is generally recommended that children under the age of 12 be seated in the rear seat.

The back seat is clearly the safest place for your child, but where is the safest rear seat position (left, centre, or right)?  Parents most often place their child in the rear right seat as it allows the driver better access to the child. However, research suggests that the rear centre seat location is the safest location as there is more space between child and the side of the vehicle in case of a side impact collision. Children in the centre seat position were found to have a 43% lower risk of injury than those in the left or right position.[6] Furthermore, children in the rear centre seat have a 9 to 24% lower risk of death when compared to child occupants in the left or right seating positions.[7]

While child seats are generally effective in reducing serious injuries for all collision types (frontal, rear, side impact, rollover), there are still steps that can be taken to keep children safe. In order to ensure the safety of infants and children during collisions, it is important to select a child seat appropriate for their size and weight and to properly install it in the rear centre seat when possible.

References

[1] https://www.tc.gc.ca/eng/motorvehiclesafety/safedrivers-childsafety-car-time-stages-1083.htm

[2] http://www.mto.gov.on.ca/english/safety/choose-car-seat.shtml

[3] K. Weber., “Crash Protection for Child Passengers – A Review of Best Practice”, UMTRI Research Review, 2000

[4] Glass et al., “Child Passenger Safety: Decisions about Seating Location, Airbag Exposure, and Restraint Use”., Risk Analysis, 2000

[5] R. Hanna., “Children Injured in Motor Vehicle Traffic Crashes”, NHTSA, 2010

[6] Kallan et al., “Seating Patterns and Corresponding Risk of Injury Among 0 to 3 Year Old Children in Child Safety Seats”., Pediatrics, 2008

[7] Braver et al., “Seating Positions and Children’s Risk of Dying in Motor Vehicle Crashes”, Injury Prevention, 1998

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