Question Question regarding Steven Levitt Ted Talk and car seat requirements?



Okay, I want to apologize in advance because I know that probably most people on this forum are so over it when it comes to having to deal with this guy. I have seen lots of info debunking his statistics. However, there was another part of the Ted Talk (I didn't read the book . . .) that I haven't seen debunked or addressed anywhere and it's still bugging me. I am hoping someone can help me wrestle with this.

I am perceiving a conflict between two things:

1. All car seats are equally safe because they all pass FMVSS standards.
2. Steven Levitt put a 3-year-old dummy in nothing but a seatbelt and it passed the standards.

If the standards are so lenient that a lap-shoulder belt could be deemed safe enough for a 3-year old, then how can all car seats that meet those standards be deemed equally safe?

It doesn't make me want to put my kid in nothing but a seatbelt. It makes me fretful that the threshold for "safe" car seats is set so low that a lap-shoulder belt can pass for a three year old.

There must be something about this that I am missing. Can anyone help?


Admin - CPS Technician
I'm in a hurry but I'll do my best to answer as quickly and thoroughly as I can, and I'm sure others will be along to add their two cents.

All car seats must pass the same standards. That doesn't mean they're all "equally" safe, just that they're "at least" as safe as they need to be.

Now, there's really no way to determine if a seat is safer than another. We can look at numbers, but that doesn't necessarily tell us much. A seat that gets higher/lower numbers in one category might get different results in another. The numbers might be different in a different car (we only have numbers from a test bench), with a different sized child, or in a different type of crash.

Plus a number that looks "better" on paper might actually have negative results in a real-world crash. (In some cases, a reduction in one type of movement might lead to increased numbers in another area.)

As for a three-year-old in a seatbelt, I remember reading that the child stayed in the car. I don't remember reading that the dummy passed the crash test criteria. Even if it did, that doesn't say much. It's quite possible the dummy met the tested requirements (head excursion, chest Gs, etc.). However, crash tests don't measure things like abdominal or spinal injuries, which a three-year-old in just a seatbelt would be likely to suffer due to the belt not fitting. And that assumes that the three-year-old would even stay positioned in the seatbelt before hand, which is unlikely.

So, bottom line: Crash test dummies aren't children. We can't determine how safe any seat will be in any particular situation. We do the best with what we have to make the best informed decisions we can. And three-year-olds need child restraints.
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This is the video I saw:

In the video he says "you have to score below a thousand to be approved" and he says that the comparison car seat installed by a tech was at about a 450 (which he calls "above average") vs the seatbelt only, which scored a 500. He says that if you took that data to the federal gov't, if they didn't know that it was a lap-shoulder belt they'd call it "a fantastic new car seat" and approve it.

If I am understanding you correctly though, LIsmama810, then the abdominal injuries to young children are not taken into account by the "under 1000" rule. So the fact that the gov't standard doesn't test for this is a moot point -- the ratings were not intended to be used on systems without a 5-pt harness?

I think I get it. The crash test is only testing for passenger retention? It doesn't test for everything that the federal standards require?


Admin - CPS Technician
There are different standards for rear-facing seats, forward-facing harnesses, and boosters.

With something like a booster, we always stress that parents look at the way it positions the belt over that particular child in whatever seating position it will be used, precisely because the crash tests can't take fit into consideration (because each child is different, seatbelt geometries are different, etc.).

That's why the IIHS conducts an annual survey of how well booster seats fit. Even that test is severely limited because they only use the 6-year-old dummy, so again, it doesn't take into consideration children of other sizes, but at least it gives an idea of how the belt might fit. There are some boosters out there that tend to provide HORRID fits on most children, and therefore usually aren't a good choice despite the fact that they pass testing. But even those boosters do work SOMETIMES.

For the record, ideally the seatbelt will fit low over the hips (not crossing the tummy) and the shoulder belt will touch the child's body and cross in the middle of the shoulder (not across the neck or hanging off). It's just not possible for every booster to fit every child in every car, so parents do need to be vigilant.

Also, when I mention abdominal or spinal injuries, I don't mean mere bruising. Children have died of internal injuries and have been paralyzed due to improperly fitting lap belts cutting into their abdomens in a crash, and even severing the spinal cord. That's why belt fit is so important, and why a child that small shouldn't be in just a seatbelt. (Children that small also tend to have the shoulder belt crossing their necks or even faces, which means that they'll likely put the belt under their arm or behind their back, which means their upper body is no longer restrained, which can lead to head injuries or possible internal decapitation.)

Now, all that said, does that mean that federal testing standards couldn't use some improvement? They definitely could. But at the same time, it's just not possible to test every possible scenario.

I haven't had a chance to watch the video by the way, so I apologize for that.


I am a safety engineer in the automotive industry with a specialty in car seats (not the removable car seats for children, but the ones that are built into the vehicle that every passenger rides in). I realize this thread is a few years old, but I have a point I'd like to add in case anyone comes across this thread. Automotive companies design the seats in their cars to meet federal regulations that assume a person's head reaches a certain height (approximately the size of a small adult female). Seats are designed so that the head hits the head restraint (or headrest as it is commonly known) in an accident. If a small child is not in a booster seat, they risk hitting their head on the seatback instead of the head restraint. These seatbacks are typically much more rigid than the head restraints because they are optimized for a different part of the body. They are not designed to have a head hit them. Depending on the severity of the accident, the child could sustain a concussion (or worse). I have 2 children of my own, and I will keep them in booster seats until they are tall enough to sit safely without them, which means following the standard recommendations.

There are additional concerns with having a small child belted directly without a booster, but I have seen them addressed elsewhere (ex: improper belt fit resulting in abdominal injury, incorrect alignment of side airbags, etc.).

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