I'm a Child Passenger Safety Technician (CPST) in the United States and can speak on seats here. Unfortunately, there are no standardized safety ratings in the United States. It is up to each manufacturer to meet and test their seats to certain federal guidelines, and the National Highway and Traffic Safety Administration (NHTSA) enforces them (recalling seats that do not pass the guidelines). So while all seats must meet the same criteria and pass the same tests, we don't know if any seats exceed these marks. What we do know from the NHTSA sled test is that the crash simulated in the test is a pretty traumatic one, so any properly used and installed seat is a safe seat. That said, the NHTSA test does (IMO) need to be updated, and a few years ago Consumer Reports did try to make a more modernized sled test, which did yield some interesting results. I haven't personally used their results to steer me towards buying a particular seat, but if it made you feel more at ease to do so, then the only 3rd party test I have found to seem to have some merit is the Consumer Reports one. When watching sled tests, they can seem jarring and dangerous, even when the seat is used correctly. A trained eye can pinpoint actual concerns, while many sled test YouTube videos seem to create unnecessary concern. We do know from European tests that certain bells and whistles can help distribute crash forces differently (anti-rebound bars, fixed anchor connectors, load legs, etc), which might exceed NHTSA guidelines. European seats are made differently than American ones, so we don't know how much (if at all) those features can help for American consumers, but they can be something to keep in mind when buying. Ultimately the safest seat is one that is properly used, properly installed, and fits safely in your vehicle (not all seats fit in all vehicles!). I definitely recommend meeting with a CPST locally before having a baby to make sure that you understand how to use and install your seat. Over 90% of infants leave the hospital with one or more errors to car seat use, and I'm a huge proponent for drastically changing that statistic! More on reddit.com

Re: Highest CRASH TEST ratings for car seats per previouse post by stayinhomewithmy4; you had said "Car seat crash test results are not published in the US." can't one get those results through Freedom of Information Law (FOIL)? It is a government agency, isn't it? I think these results... More on car-seat.org

An observation as a car mechanic who has had a child recently. Most child seats are IMPOSSIBLE to install correctly according to their own directions. The local fire department certified guy is always unavailable. I am beginning to think it is a feature, not a bug. More on reddit.com

The IIHS and NHTSA do their crash testing differently, and it's based on what they find from their different testing. Different things come up in different way of crashing.

For frontal impact, the NHTSA crashes a car head on straight front at 35 mph. The IIHS tests at an offset, so one of the tests is at half of the car impacting the barrier, and another test is at 1/4 of the car doing so, and both at 40 mph. These different ways of testing can show different things than other tests.

Same with the side. I believe the IIHS's side testing simulates as if an SUV was to hit the side of the car, at 31 mph. The NHTSA does their side barrier test as if its a 3000 lb car (different dimensions and energy dissipation) was to hit the side of the car at 38.5 mph. Again, the different speeds, different "footprint" of the barrier on the car, and different weights of the barrier all contribute to different results.

There's also differences in evaluation, since there are no published "bright line" results of what constitutes what rating.

In short, they're both useful, they just test different things.

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