car laying

My son layed down in the back seat of the car yesterday.
I told him it was safer in an accident to be lying down instead of setaed and buckled. Am I right?

That would be seated.

I’d guess no; if he has no seat belt on, then in an accident he becomes a projectile. If he does have a seat belt on and he’s lying on his back, he’ll be bent violently sideways at the waist, which his body isn’t meant to do.

Tapping all my physics knowledge, I can’t seem to find a situation where being free to move within a car would be safer than being belted as a “part” of the car.

Lets say you are moving at speed v and kiddie has a mass of m. He has to dissipate momentum mv during/after the collision. Thanks to the conservation of momentum law (which can’t be repealed), he can’t just make it disappear. It would always be better if he were belted in the car. Sure the new mass would be larger (m + M where M is mass of car) but he could dissipate his portion of the total momentum with the car. (does that make sense? If not, I’ll go ahead and calculate it - heck, it might give me a chance to use the new symbol font!)

This is anecdotal evidence only, but my uncle was in a car wreck where he was lying down in the back seat, and was the only survivor. I don’t know the details of the wreck, but it was pretty bad. The driver and passenger were killed, and my uncle survived only because he was flung through the rear window (after some car spinning, I presume). Even so, his back was broken, and he was almost paralysed. Still walks with a waddle.

So, in at least one case, it was safer to be lying down in the back seat than buckled up. “Safer” being entirely relative.

With all due respect, this is a useless example. Were the front-seat passengers in the car buckled in? What sort of damage was there to the car? Front? Back?

Without those answers (which you admitted you don’t have) drawing a conclusion like you did, even for that one particular instance, is wrong.

Getting back to the OP, depending on the type of accident, the kid could find himself slamming (uncontrolled) into the back of the front seats, either door, the roof, or going out a window. IMO, all worse than hitting a seat belt.

I have a younger brother that was laying down in the back seat of a car that rolled over. He went throught the rear window and was thrown about 15 ft. from the car. He also got hurt the worst than anyone else. FYI it was a long time ago and he was fine soon after.

safer buckled

By the way, not only is it unsafe for the passenger to be lying down (or unbuckled at all), it is unsafe for the rest of the passengers in the car. If the person sitting next to you in the car turns into a projectile (due to his/her not being buckled in) there’s a chance that their body will impact yours and cause additional injuries to both of you.

At least, that’s what they told us in AAA Driver’s Ed class.

Not only is it not safer to be unbuckled and lying down, it is illegal in most states.

Couldn’t you argue that a person who sits in the back seat is blocking the driver’s view and increasing the risk of an accident? Therefore, a person lying down may be better off. Maybe they need a different belt design.

In a related story, I was blamed for a speeding ticket that a girl got one time because I was “blocking the view of the cop behind” her. My position in the car apparently affected her right foot.

You could, but I think you’d be wrong. I’m having trouble thinking of a time when someone sitting in the back seat blocked my view of anything I needed to see on the road. Occasionally when I need to back up out of a parking space, I’ll ask someone sitting in the back seat to duck down or scoot to the side slightly, but that’s about it.

Besides which, if there is a risk incurred by sitting upright in the backseat, that risk is incredibly tiny compared to the danger you’re putting yourself in by riding without a seatbelt.

Thanks for the info, though once he sat way down on the floor of the back seats, whichs eemed much safer.
But he will buckle from now on, don’t worry.

In the back seat? Do you have a cite?

[FWIW Australian context]
In NSW all vehicle occupants older than 14 must wear seat belts. Babies under 12 months must be in an approved child restraint or child. Children between 1 and 13 years must wear a Child Restraint or a Seat Belt if one is available.

Onus for this is on the driver. NSW Motor Accident Authority

In time for the public holiday last weekend, regulations were in the place so that if two or more occupants of a vehicle are found not wearing seatbelts, the driver will lose their license.

[/Australian context]