When to let a 'child' sit in the front seat based on age or weight?

This came up in a fb group I'm in and I was wondering what everyone thoughts are on it.
We all know the minimum for letting kids ride in the front seat is 13 years old. The question was asked if that's because of build or because of age. Hypothetically say you have 2 kids one is 12 and 14. The younger one is bigger height and weight wise. If you had to put one or the other in the front, which would be best?

If the younger is bigger height and weight wise, that'd be the one I put up front. The mechanics of it is body placement in relation to the airbag. The bigger child would have a better placement than the smaller one.

ETA: Height would play a bigger part in my decision than weight. Of course, just because the 12 year old is taller, doesn't mean the 14 year old would be in any more danger than a 12 year old or adult...I guess I'd have to see the kids or at least know height/weight specs.

Good question!

I think just like booster riding, maturity comes into play as well. Which would be less likely to be sitting out of position? If that were equal, I'd probably go with the bigger kid.

Assuming both were big enough to fit the belt properly, I'd put the older one up front. If the smaller one did not fit well, the one who fit would ride up front even if s/he was younger.

My understanding is that it's part size, and part bone maturity.

I don't even let my husband ride in front, lol. I am not kidding, as you know.

He has a lap and shoulder belt back there and if that's the safest spot, so be it.

I don't anticipate ever putting a pre-teen or teen up front.
If we do ever fill the van then husband would have to sit in front, I guess.

Bone maturity plays a role, as does behavioral maturity, as does size. I personally don't think there is a magic age, since kid's mature at different rates.

For my car, once a child is the size of a small adult, and can sit properly, I'm comfortable with front seat riding *when needed. There have been studies that show that the seat belt kinetics are substantially better in the front seat than the back, and that front seat occupants are much less likely to suffer seat belt related injuries. The kind of airbag injuries we see in properly restrained and seated adolescents are mild, usually involving fractures to limbs.

*reasons I would consider letting a child ride in front: better seat belt fit, child prone to car sickness, more kids than back seat lap/shoulder belts, no head restraints in back seat, back seat needed for hauling stuff

My 11yo (5'1") son rides in front when the front is available in our Corolla. The belt fit is much better and he is too tall to have head restraint in the back with a booster. My 9yo DD (4'8.5" 5 steps except while sleeping) is allowed in the front if the situation warrants. Such as when I pick up a group of girl scouts and I need to choose someone to go in front. One of the other girl scouts is 10yo and 5'5" tall, but I won't allow her in the front because she won't stay in position.

Depending on the vehicle, I'd say the front seat is sometimes a *safer* choice. For example, in my car I will not let an adult ride in the back unless it is unavoidable due to the lack of headrests and poor belt fit. With a 12 and a 14 year old, provided they both fit equally well and maturity wasn't a deciding factor then I'd let them take turns or even better, keep them both in the back if possible.

My 11 yr old rides in front pretty much every time unless DH is with us. She's 5'3'' (with a size 10 womens shoe OMG LOL), not sure on weight TBH but she's a size 1 or 3 depending on brand. It's that or she's mashed between two car seats and the younger kids trying to touch her book or DS or whatever. Waaaay distracting for me.

Mia wasn't allowed in the front until she hit 13. At that time she was over five feet and nearing 90lb.

Now that we're in a van, they all prefer to ride in the back, because there's more space than the sedan we used to have.

There's research that shows age is more important than size. This article sums up a study that found that kids under the age of 15 are safer in the backseat, regardless of size.

From the article:

The study found that children 14 and younger were at high risk for serious injury from air bags when they sat in the front passenger seat during car crashes.

In contrast, air bags had a protective effect for teens aged 15-18. And the study showed that age may be a better indicator of risk from air-bag injury than height or weight.

[Dr. Craig] Newgard and co-author Dr. Roger Lewis, an emergency-medicine researcher at the University of California-Los Angeles, said several body changes that take place during puberty, including muscle mass, bone density and bone-mineral content, may help explain why body size alone isn't a good measurement of risk from the air bags in children.

"Anyone who drives needs to be empowered with this information," said Newgard. "When my 13-year-old nephew wants to sit in the front seat now, I won't let him."