Seat belt failure

nhlbluesgirl

New member
Would the top tether help in the event of seat belt failure (harnessed FF seat)? I realize that seat belt failure is rare, although it does happen (Kyle Miller). My thought is that as long as the child is properly harnessed, the top tether would keep him/her in the vehicle at least. Is that a correct assumption? :confused:

ETA: sorry about the typo in the title :doh:
 
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Jeanum

Admin - CPS Technician Emeritus
Staff member
Re: Seat belf failure

The top tether on a harnessed carseat simply isn't designed to serve as the primary attachment to the vehicle, and there's really no guarantee it would keep the child seat secured to the vehicle in a crash in the event the seatbelt failed. It might, it might not. The main role of the top tether is to reduce head excursion and it's always advisable to use it for a harnessed, forward facing carseat if the vehicle is equipped with an appropriate top tether anchor. There's an excellent article at Safety Belt Safe USA's site to help reassure about the rarity of seatbelt failure, and importance of following best practices in child passenger safety: http://www.carseat.org/Resources/650_YouTube.pdf :thumbsup:
 

nhlbluesgirl

New member
Re: Seat belf failure

The top tether on a harnessed carseat simply isn't designed to serve as the primary attachment to the vehicle, and there's really no guarantee it would keep the child seat secured to the vehicle in a crash in the event the seatbelt failed.

I completely understand that. :) I was just having a "what if" moment. Thanks for the info! :D
 

lovemyfamily

New member
Re: Seat belf failure

Like Jeanum said, it isn't meant to be the primary attachment of a carseat, I sure would feel better knowing it is there, should the seatbelt fail, as in Kyle's case.
 

jen_nah

CPST Instructor
Like Jeanum said there is no way to say for sure the child restraint will stay in the vehicle. Even if it did you now have a HUGE projectile in your vehicle that will do severe if not deadly damage to other occupants.
 

spcamno

New member
I hope I don't get flamed by your guys but what if I use both?

I mean using tether with the latch along with the auto's seat belt as back up?
 

snowbird25ca

Moderator - CPST Instructor
I hope I don't get flamed by your guys but what if I use both?

I mean using tether with the latch along with the auto's seat belt as back up?

Car seats aren't tested this way, so in essence installing a carseat with both the lower anchors and the vehicle seatbelt is turning your child into a crash test dummy. Most carseat manuals specifically warn against using both to install a carseat - going against the manual's instructions also voids all liability the carseat manufacturer could have if the seat failed.

Seatbelt failure is so incredibly rare, but if you're worried, then you can always move the seat to an outboard position and install it with the lower anchors and just don't use the seatbelt.

I did a check shortly after becoming certified and the carseat was installed using both LATCH and seatbelt because they'd been unable to get a tight installation with just the one. When I unbuckled the seatbelt, the carseat was incredibly loose. In all likelihood it would've worked the other way too if I'd removed the lower anchors first. Another thing that happened, was the harness had been harder for them to adjust when the seat was installed with both - they didn't even realize it was harder until the seat was installed with only the one method and they adjusted the harness.

There are other issues too - I'm sure you could find a whole bunch of threads if you did a search. It's a question that comes up fairly often.

And as a general rule, we don't flame people around here. The techs and advocates around here are really only interested in helping educate and answer questions that parents & caregivers have. You'll find most discussions offer facts and recommendations, above and beyond that it's up to the parent. We all like to see parents make the safeST choice, but it's ultimately their decision and isn't for us to judge. :thumbsup:

FWIW, a seat being installed with both the lower anchors and vehicle seatbelt is probably one of the most common misuses when it comes to LATCH - the first one being borrowing anchors in vehicles that don't allow it. So you're certainly not alone in wondering if one would be good back up for the other. But until a manufacturer starts telling us to use both when installing a seat, I'd leave the testing up to them and just choose one or the other. ;)
 

wendytthomas

Admin - CPST Instructor
Staff member
What Trudy said. :)

I wanted to add that one of the suspected reasons that it must have failed testing is that when using both systems neither worked properly.

In a collision the seatbelt or LATCH strap will stretch up to 20%. This allows for more ride down time, it slows the stop down. You'd rather flop back onto a mattress than a board, right? The mattress gives, it doesn't stop you at once. Same thing with the restraint (and then the harness or seatbelt as well, but that doesn't matter here).

If you use both of them it's quite possible that the seatbelt things that LATCH has it and LATCH thinks that the seatbelt has it and neither one stretches at all, or not enough. Then all of the forces that would be spread out over the 20% stretching are transferred to the seat and your child. The seat wasn't designed for that and your child wouldn't appreciate it.

Wendy
 

ThreeBeans

New member
Although the tether is not designed to withstand the forces of an accident alone, and won't allow the carseat to work effectively in preventing head excursion if the seatbelt/lower anchors fail, it is my *personal* belief that the third point of attachment, in the rare event of a failure, would at the very least keep the child inside the vehicle rather than being ejected from the vehicle, which of course is always preferable.
 

southpawboston

New member
In a collision the seatbelt or LATCH strap will stretch up to 20%. This allows for more ride down time, it slows the stop down. You'd rather flop back onto a mattress than a board, right? The mattress gives, it doesn't stop you at once. Same thing with the restraint (and then the harness or seatbelt as well, but that doesn't matter here).

If you use both of them it's quite possible that the seatbelt things that LATCH has it and LATCH thinks that the seatbelt has it and neither one stretches at all, or not enough. Then all of the forces that would be spread out over the 20% stretching are transferred to the seat and your child. The seat wasn't designed for that and your child wouldn't appreciate it.

Wendy

then what does this imply for rigid LATCH seats? i thought that the more tightly coupled the restraint is to the car, the better. there is no stretching with rigid LATCH.

but i agree that you can't use LATCH + seatbelt simultaneously, as they were not tested that way. but i do not believe the ride-down argument.
 

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