Why ride rear-facing?

Posted in: Rear-Facing Seats

Sitting rear-facing is simply the safest way to sit in a car. Research shows that the risk of small children being killed or seriously injured is five times higher for those sitting in forward-facing seats than for those in rear-facing seats. New data demonstrates that in a side-impact crash (the most deadly type of collision) rear-facing kids are 4 times safer than those riding forward facing.

Physics: Adults vs Kids

In a crash you always go towards the point of the impact. In a frontal crash, everyone moves toward the front of the car. If you are forward-facing–either in a car-seat or a safety belt–your upper body stops quickly as the chest strap on the car seat or seat belt holds you back. However, your head doesn’t stop as quickly, but rather travels all the way forward until your chin touches your chest, and then goes all the way back – whipping forward and back in the blink of an eye. Since an adult’s head is just 6% of their body weight, you can withstand having your head pulled violently away from your body. It’s quite different for a newborn, whose head is a whopping 25% of its body. This means that if a newborn were forward-facing in a frontal crash, their head would pull forward with four times as much force as would an adult’s!

Strength and rigidity of the bones in the spine also contribute to how well you can tolerate your head being pulled forward and back in a crash. The bones of an infant’s spine are made up of soft, stretchy cartilage – the same thing that makes your ears and nose flexible. The ligaments that connect these cartilaginous bones are also underdeveloped and stretchy. Scientists have found that a newborn’s spinal column (bones + ligaments) can stretch up to 2 inches, whereas the spinal cord inside can stretch only 1/4 of an inch. If the spinal cord is forced to stretch more than it can, it breaks, leaving the baby paralyzed or worse.

Physics: How rear-facing works in a crash

In a frontal crash, when everyone moves to the point of impact–the front of the car–a rear-facing baby will move in a different way. A rear-facing baby will move into the back of his car seat and will slide gently up the car seat. This allows the back of the car seat to absorb the brunt of the impact and distribute the remaining forces along the child’s entire back, which is the strongest part of his body. The most important part: because he sits rear-facing, the child’s head, neck, and torso all move together in a straight line. The whiplash motion is avoided totally.

courtesy of the University of Michigan

This video shows two crash tests of properly installed car seats – one rear-facing and the other forward-facing – in a frontal crash. Note that both dummies are properly secured in the car seats (i.e. the harness straps are snug). The rear-facing dummy’s head and back are cradled by the back of the car seat. The forward-facing dummy’s head and neck are thrown forward in the whiplash motion. Rear-facing seats also protect children better during side-impact crashes (the most deadly types of crashes). In a side-impact, everyone moves toward the impact. A forward-facing adult or child will pivot around their pelvis and turn to the side, leaving their head at risk for hitting the doorframe, window, other hard structures, etc. When a child is rear-facing in a car seat, the car seat itself does the pivoting, allowing the child’s body to stay in a straight line. And since his head usually does not extend beyond the sides of the car seat, his head is better protected.

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