Why is a 5pt harness better than a 3pt?

[ellies mom]

My friend used a 3-pt harness bucket seat with her last two. She is pregnant again. I suggested she replace the bucket seat with one with a 5-pt harness. Her husband doesn't feel it is necessary. His reasoning is that since the seat is rear facing the back of the seat is doing the restraining and the "extra straps" aren't necessary. She is going to let it rest for a bit and bring it up again later so I was hoping to have some info that she could use at that time. Her back up plan is to just go buy one but she'd rather they both be on the same page. Thanks.

[Joolsplus2]

I'd be worried that a three point infant seat is expired by now, primarily...or possibly recalled. It's not a *huge* safety difference, no...but they don't test them in side impacts, either... A tech instructor friend of mine has seen a crash test where that baby just flies sideways out of a seat in a side crash... that's something they just don't have to test for NHTSA standards to make it onto the market. Also, real life babies wiggle more than test dummies and sometimes the little ones just slip right out of that harness :(. Newer seats also have head protective EPS foam and are a lot easier to install and get the harness tight than old seats.

Anyway, just some thoughts...

[codex57]

Has he never been in a car accident? When you get into a car accident, the initial impact throws the body in one direction. However, the car (and everyone in it) will then snap back the other way. It may not have as much force as the intial impact, but it can still be significant. It's what causes whiplash. I think the Volvo website has some great vids on it. Since kids don't have the upper body strength of an adult, they can't withstand the secondary motion as much.

I guess a simple way of warning them is: "A 5-point harness helps against whiplash more than a 3-point one". Yes, the head and neck aren't protected in either, but the upper body is.

Or, if he's a race fan: "Nascar/F1/Indy drivers use 5-point harnesses because it's safer than a 3-point, so why shouldn't your kid?"

[GeekLady]

The body has two structural girdles, the pelvic girdle, and the shoulders (I forget the fancy name, sorry). The shoulders do not form a complete bony circle around the torso, they are open in the back to provide flexibility. They get away with this because they don't bear a lot of weight. The pelvis does form a complete circle, and the bones are much stouter, because they are built to bear and distribute the weight of the body.

A 3 point harness will distribute force to the shoulders, the weaker girdle. A 5 point harness will redistribute some force to the pelvis. You can't take ALL the force off the shoulders, the upper torso must be restrained, but anything you can redistribute, especially to a stronger bone structure, is A Good Thing.