Take a look at this. There were five people in this mini-van. Look at the damage, and then ask yourself "How badly were the people in this vehicle hurt?"
The most serious injury? A severe cut on the foot & broken leg to one of the children.
Part of the story:
On our way to Phoenix, just a few miles away, my husband (driving our 2002 Odyssey) hit an obstacle in the road. We don't know what it is, but we all felt the bump, then were airborne, and onto a gravel shoulder. We skidded on the gravel. The van hit a barrier (right at the rear driver's side, where my 4 year old daughter was seated.) It then flipped across the highway. My husband was braking the whole way. (He had just had the tires rotated and pressure checked, and the brakes replaced.) It slowed us considerably. We went into a ditch at an angle and became airborne. We went down on the passenger side of the vehicle, nose first, and then flipped over upside down.
Go. Read the whole thing. Look at the rest of the pictures. The most serious injuries were to the four-year-old whose door took the initial impact with the barrier. There was a rear-facing toddler--well old enough to have been turned around by the legal guidelines in most states--whose legs were undoubtedly pretty scrunched-up, but who escaped without the tiniest injury.
I'm not as good with carseats right now as I'd like to be; I'm as good as I can be, realistically. I hope only that everyone can do their best.
There was more to the survivability of that accident than just carseats. Y'all--keep your brakes in good condition, keep your tires aired up, keep your seatbelt and head-rest properly adjusted. Lock down packages as best you can. (This is something we need to work on. Past time to clean out the truck.) Even the best driver cannot account for everything. Not every wreck can be avoided (I just read an article a while back about a young mother who was killed when a chunk of asphalt thrown from a poorly-repaired pothole by another vehicle came through the windshield). So do your best to mitigate the damage that will come if it does happen.