As I understand it, in the US it is advised that children weighing less than 40 lbs should be seated in a rear-facing car seat and those weighing less than 22 lbs must always be placed in a rear-facing car seat. However, it is also advised that children weighing over 40 lbs should be seated in a forward-facing car seat (some jurisdictions may have additional criteria).
What happens at 40 lbs that makes a rear-facing car seat suddenly unsafe when it was mandatory below 22 lbs?
Thanks.
There’s no magic about 40 lbs. Everyone is safer facing backwards. That’s why the flight crew on an aircraft usually sits facing backwards – to maximize the odds they can be helpful if there’s a crash.
It’s just a question of when a kid gets too big to comfortably fit backwards, where (in a typical set-up) there isn’t a lot of legroom, there’s no view, etc.
In the UK there is no law that says children have to face front or rear at any age, although rear-facing seats must not be used if there is an operative airbag.
Up to 3 years old they all have to be in an approved child seat. Then, until they are twelve or135cm tall they just have to use an appropriate child restraint.
Actually, my guess is that the reason for the 40 pound limit is that rear-facing car seats are tested up to 40 pounds, and not above that. I assume that’s the regulation good-through weight.
Much of the reason has to do with the skeletal development of the child. It takes awhile for the bones to knit together and get strong enough to allow strap based restraints to hold a child in place during an accident.
So as said, rear facing is safer, but runs into practical limitations as the kid gets bigger. At some point the skeleton is strong enough to be restrained in a five point harness in a forward facing car seat. Later the child gets big enough for a standard lap and shoulder belt to be effective in conjunction with a booster seat.
Each step does probably sacrifice some safety for practical concerns. If safety were the only issue, we’d all be wearing five (or six) point harnesses, and never exceeding 30 miles per hour.
I just looked up the official US government guidance, and it doesn’t say “40 pounds”, fwiw. Rather, it explicitly refers to the height and weight limits of the car seat.
Keep your child rear-facing as long as possible. It’s the best way to keep him or her safe. Your child should remain in a rear-facing car seat until he or she reaches the top height or weight limit allowed by your car seat’s manufacturer. Once your child outgrows the rear-facing car seat, your child is ready to travel in a forward-facing car seat with a harness and tether.
It’s seems obvious that you are safest in a car seat that is rated for your size and weight. Otherwise, the seat might fail in a collision, breaking or otherwise not protecting the occupant.
From the link below see page 19 of the Instruction Manual of the car seat we recently purchased:
It cites the NHTSA and the AAP and states “4-22 lb (1.8-10 kg) less than 1 year old MUST be rear-facing” while also stating “40-65 lb (18-30 kg) SHOULD be forward-facing.”
I would think there are some design problems with a backward-facing seat for a larger child. Their legs have to go somewhere. The government could mandate it; for that matter they could mandate that all occupants are rear-facing except the driver, but they have to draw a line somewhere.
My kids were definitely having trouble with where to put their legs long before they reached the proper age/height/weight to turn their seats forward. Keeping them rear-facing longer would have been problematic.
Where I grew up this was rear facing seating:
