• Original Articles By Dr. Lavin Featuring Expert Advice & Information about Pediatric Health Issues that you Care the Most About

    Sitting Safely in the Car- A Primer on Car Seats, Booster Seats, Seat Belts and Shoulder Belts

    By Dr. Arthur Lavin

    We love our cars, especially the mobility they give us all.

    And, we spend so much time in them, we become unaware of how fast our bodies are moving in space.  This is not a strange gap in perception, after all we spin around our axis at a speed of 1,000 miles per hour and fly around the sun at 67,000 miles per hour, and no one can feel us moving at all, even at these speeds.

    So as we and our children fly through the air at 25 or 35 or 60 miles per hour, it seems like we are all safe and snug in our car.  But the fact is that we are moving very fast in space when we drive around with our kids.

    Cars Are Built Well, but Really for Adults

    The good news is that cars are far, far safer than they ever were, for adults.  The sequence of innovation of seat belts, shoulder belts, safer construction of the vehicle, and air bags, has yielded sharp drops in the number of injuries and deaths from car accidents.

    As we all know, the people who buy cars are all adults, so they are designed for adults.   A good example has to do with the car’s original seats and your knees.  Next time you sit in your car, sit comfortably with your back snug against the back of the car’s seat, you will notice your upper legs extend beyond the edge of the seat, your knees will be past that edge with nothing but air underneath them.  This allows your knee to flex comfortably, setting your feet in the floor.

    For most cars, if you are shorter than 4’9″,  and you sit in the car’s original seat, your knees will not reach beyond the edge of the seat, this makes a person slide their bottom forward so the knee can reach the edge, otherwise the lower leg and feet are stuck sticking out in air, a very uncomfortable position.

    Again, the adults who buy cars tend to be taller than 4’9″ so there is no problem.

    But no young child is that tall, and so an issue of fit is present.  Let’s take a closer look at the problem of fit.

    The Notion of Fit

    Fit in a car can be a matter of life and death.

    If you properly fit, then the restraints work and if the car hits something or changes speed suddenly the person, no matter what size, as long as the fit is right.

    Making Sure Your Newborn and Infant Fit

    It requires no stretch of imagination to know that a newborn and infant cannot fit in a car without an adapter.

    The adapter that allows them to fit is called a car seat, or infant car seat.

    Car seats are complete adapters, meaning that we concede the car’s original seat cannot possibly fit the child appropriately, so a whole new seat is placed in the car, a seat built to fit the baby.

    These car seats are rated for the size of your baby, for one very good reason, so they fit, and they will protect your baby if a car accident occurs.

    Most car seats are built to handle babies up to 40 pounds.  So these car seats are the solution from birth to 40 pounds.

    The seats provide the best protection if your infant faces backwards up to age 2.  This drops the risk of death from a car accident 5 times!

    Older children

    Not only is weight an issue for fit, but so is size.  So if your toddler is under 40 pounds but can barely physically sit in the car seat, it is too small, you need to get a larger one, even it is rated for the same number of pounds, 40.

    For children age 2 and over, you should be facing forward.

    Many parents, and especially kids, think, why if I am 4 years old, should I sit in a baby seat???

    The point is that the car seats are not baby seats, they are adapters.  They are designed to allow a person smaller than an adult to sit in a car safely.

    If an adult weighed 38 pounds, they would need to sit in a car seat to be in a car safely.  Otherwise, if there was a car accident, the car as it is manufactured would offer little protection.

    So it’s not a baby seat, it is an adapter for everyone who weighs less than 40 pounds, no matter your age.

    If companies made an adapter that could hold anyone at any weight, even up to 200 pounds, then we would all need to sit in that adapter until we were 4’9″ or taller.

    But companies tend to make the adapter fit for only kids 40 pounds or lighter.

    So there is a gap between being 40 pounds and being 4’9″.

    In that gap, a child cannot sit safely with the car’s original seat, seat belt, and shoulder belt.  Remember the discussion above, about how the knee wants to go over the edge of the seat of the car?  What if you weigh 42 pounds and are only 3’8″ tall, your knee will not reach the edge of the car’s seat, and you will always slide your bottom forward til the knee does reach, so your legs can drop.  That makes the seat belt ride up on your belly.

    If that ever happens, and you have a car accident, the seat belt will no longer help, it will hurt.  The belt only works if it is wrapped around your pelvic bones.  In that position it can hold you.

    The other issue with the gap (the time you are over 40 pounds but shorter than 4’9″) has to do with the shoulder belt.  Most people shorter than 4’9″ will have that belt ride on their neck.  Need we say more about that?

    The Goal ALWAYS- Good Fit- Pelvis held by a belt, Clavicles (shoulders) held by a belt

    The reason this goal is so clear, and so very valuable, is that as long as people drive cars, they will crash into each other and various things.

    That sudden drop in speed can hurt people terribly, unless they stop too.  If a belt holds your pelvis and clavicles, you will stop, and injury and worse will be prevented at an astoundingly good rate.


    1. Cars are safer now than ever- better belts, better construction, air bags
    2. But they are built to deliver safety for people 4’9″ or taller.
    3. For EVERYONE shorter than 4’9″, the car is not safe to ride in, you do not fit the seat belts and shoulder belts.  You will need some sort of adapter to fit.
    4. For those under 40 pounds, the solution is a complete adapter, a plastic shell that creates a seat that you can fit in totally.
    5. For those over 40 pounds but shorter than 4’9″, the solution is a booster seat, it basically allows your knees to bend with your back firmly against the seat, allowing the seat belt to hug your pelvis, and the shoulder belt your clavicles.
    6. Once 4’9″ or taller, feel free to sit in the car’s original seating, no adapter needed, you fit.

    From birth up to 2 years old, sit backwards in a car seat.
    From 2 years old up to 40 pounds, sit forwards in a car seat rated up to 40 pounds.
    From 40 pounds to 4’9″  (no matter the age), sit in a booster seat.

    To your  health,
    Dr. Arthur Lavin


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