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Rear Facing Car Seats
Basics, Science, and Crash Dynamics
 
Videos

Rear Facing Basics 


Rear facing is the safest way for children to travel. It is the best way to prevent head and spinal cord injuries. 

A child should ride in a rear-facing car seat AS LONG AS POSSIBLE. It is best practice to rear face to a minimum of age 2, and ideally until the child reaches the top height or weight limit allowed by the car seat manufacturer (age 3-4), as per American Academy of Pediatrics (AAP) and National Highway Traffic Safety Administration (NHTSA). 





Statistics


Children under 2 years old are 75% safer rear facing. Children 12-24 months are 5 times less likely to be killed or seriously injured when rear facing than forward facing - that is, 532% safer rear facing. Data from Injury Prevention: http://injuryprevention.bmj.com/content/13/6/398.abstract

532% may sound like a lot, so to put it in terms of number of children: 
  • Rear Facing: In 100 collisions, 8 children will die or become seriously injured. 92 will walk away fine. 
  • Forward Facing: In 100, 40 will die or become seriously injured. 60 will walk away fine. 

Proper Rear-Facing Car Seat Use 

  • Position harness straps at or below shoulders.
  • Position chest clip at armpit level.
  • Install seat at the correct angle and through the correct belt path.
  • Child should have no less than 1" of car seat shell above their head (unless otherwise specified in the manual) 
  • Car seat should be installed with LATCH or Seat Belt, Never both (unless otherwise specified by car seat and vehicle manufacturers)
  • Car seat should be installed with no more that 1" of movement side-to-side or front-to-back at the belt path, with LATCH or locked seat belt.

Crash Dynamics: Rear-facing vs. Forward Facing 


According to NHTSA, frontal or offset frontal vehicle crashes make up the majority of all collisions.  Rear-end crashes represent about 30% of total crashes, however, they comprise only about 5% of all serious and fatal crashes, suggesting that while numerous, rear-end crashes are not especially lethal. 

This places much of the crash dynamics emphasis on frontal collision. Rear-facing car seats may not work as effectively in a rear impact, however frontal, frontal offset and side impacts are not only more common, but also account for the most percentage of fatalities. 





During a crash, occupants will travel towards the point of impact. Every collision includes three crashes:
  1. The vehicle crash - the vehicle strikes something and comes to a complete stop. The crushing of the vehicle absorbs some of the crash forces. 
  2. The human crash - when the vehicle comes to a stop, the human body continues to move toward the point of impact at the vehicle's original speed. The passenger then collides with something that brings the body to a complete stop - such as the harness, seat belt, airbag, or the back of the car seat. 
  3. The internal crash - when the occupant's body comes to a complete stop, the internal organs are still moving forward, until striking the inside of the body.

Crash forces

The force needed to restrain an occupant is approximately the weight of the occupant multiplied by the vehicle speed. So, a 10 pound infant, traveling at 30 MPH, requires about 300 pounds of restraining force to keep from moving forward.
  
When the child is rear facing, the crash forces are distributed along the entire body (head, neck and back), and the head moves with the seat, reducing the risk for neck and spinal injury. However, when a child is forward facing, the crash forces cause the head to move forward abruptly, resulting in head and spinal injuries. 


The Anatomical Science of Rear Facing 


The Spine

The human spine is made up of 24 presacral vertebrae, 7 cervical (neck), 12 thoracic (upper back) and 5 lumbar (lower back) vertebrae. The young child's vertebrae consists of portions of bone joined by synchondroses (cartilage), rather than ossified bone. Over time the portions will fuse (ossify).
 
Note in the following images, how the 1 year old (before age 2) vertebrae is still not fused. The vertebrae start to fuse together at the age of 3, and it takes until the child is 6 years old for complete closure. At age 3, there is only a 50% probability that the C3 vertebra has finished ossifying. The older a child gets, the more time their spinal column has to strengthen. 

      


The vertebrae of a young child are not developed enough to protect the spinal cord during a crash. When forward facing, in a frontal collision, the weight of the head combined with the immature skeleton, can cause the spinal cord to stretch up to 2 inches, while serious injury can occur at just 1/4 of an inch stretch. This often results in internal decapitation and causes paralysis or death. 

When rear facing, in a frontal crash, the car seat decelerates the child's body by spreading the crash forces over the back of the seat, where there is greatest surface area to absorb the forces. When forward facing, the forces are concentrated over the harness to hard points (shoulder and pelvis) of the skeletal structure. 

More in-depth info about Pediatric Spinal Cord and Spinal Column Trauma: http://www.neurosurgery.org/sections/section.aspx?Section=PD&Page=ped_spine.asp

Quantitative Analyses of Pediatric Cervical Spine Ossification Patterns Using Computed Tomography: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3256844/ 


The Head 

Infants have a larger head to body ratio than do older children, and at the same time, do not have fully developed skeletal and neck structures. That means that the crash forces will be greater at the head and neck for a younger child who is forward facing, than for an older child. The forward-facing child's torso is restrained by their harness straps. The head of the child, however, is unrestrained and thrusts forward violently, causing serious spinal cord injury or death.

Rear-facing child restraints also offer safety advantages in side and frontal offset impacts. When rear-facing in a side or frontal offset impact, the head of the child is better kept within the confines of the seat and can benefit more from the restraints side impact protection. 



The Torso 

A toddler's ribs are also very soft. In a forward facing car seat the force of the crash throws the child forward while the five-point harness holds the torso back in the seat. This can bend the ribs and damage the child's internal organs.

What if the legs are touching the vehicle seat? 


Feet touching the back of the vehicle seat is not a safety risk. Approx 0.1% of kids rear-facing will suffer lower extremity injury - the rate is higher when forward-facing. Also, kids are flexible, so it is not uncomfortable for them. 

There have been no documented cases of rear-facing children breaking their legs, hips or feet because of their feet touching the back of the vehicle seat. Even if the child's legs did break, it is much easier to cast it then it is to repair broken necks and ruptured spinal cords. 

Is the positioning of the legs uncomfortable for the child? 


This positioning of the legs is not uncomfortable for young children who naturally prefer to bend their legs anyway. Children are very flexible and benefit from being able to sit in the car seat with their legs in various configurations (criss-cross, over the sides, up on the vehicle seat, etc). More children express their discomfort about their legs dangling in one position for the entire ride when forward facing. Being able to change positions is a plus. 

Can my child forward face because it is easier for me to see the child? 


It's important to weigh the pros and cons. Convenience doesn't change the child's anatomy or the physics of crash forces. 

What if I am rear-ended? Won't the child be safer forward-facing? 


Frontal and side impacts are the most common type of crashes and also the most severe. Rear impact collisions account for only about 5% of all severe and fatal impacts. Frontal and side impacts are the most deadly type of crashes (especially side impacts), and rear-facing children are much more protected in both types of crashes than forward-facing children. In the 5% of severe rear impact crashes that a rear-facing child would be in, they have at least the same amount of protection that a forward-facing child would have in a frontal impact. 

The forces in a rear impact collision are also different from the forces in a frontal impact. In a frontal impact, the forces are much greater because the vehicles are usually traveling in opposite directions, therefore the vehicle and all occupants come to a complete stop very abruptly.  When you are struck in a rear impact, the vehicles involved are traveling in the same direction, and the vehicle that is hit in the back has room to move forward. The crash force on the occupants is much less than in a frontal impact. 

Rear-end crashes are somewhat more common in cities, high density areas, and in stop and go traffic, however these are typically low speed, and not often severe or fatal collisions. Also, in most instances, for every car that gets struck in the rear, another car is experiencing a frontal crash. Car seats and cars best protect against the most frequently fatal types (frontal or frontal offset).

In short, rear-facing provides optimal protection in the types of crashes you are most likely to be in.


Rear-Facing Videos