LATCH versus ISOFIX: differences in side impact?

southpawboston

New member
i know that ISOFIX has had a spotty implementation in europe becuase it doesn't work well in a broad range of cars for fitment reasons, and that is why LATCH has become the prominent standard in the US.

but i found this presentation which outlines test results comparing LATCH and ISOFIX and their effect on side impact, specifically head containment and chest loads:

http://www.unece.org/trans/doc/2004/wp29grsp/TRANS-WP29-GRSP-35-inf19e.pdf

warning: link is to a PDF file.

basically they conclude that ISOFIX (or rigid LATCH) does a better job at containing head movement than LATCH, because of less transverse (side to side) movement and vertical rotation of the seat. they not only tested ISOFIX versus LATCH but also top tether versus no top tether, and the results of that are interesting as well.

i have always had the suspicion that the more rigid the attachment of the CRS, the better (which is why i don't like the 1" rule for belt path movement). this report would seem to agree with that.
 
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joolsplus3

Admin - CPS Technician
Yeah, even years ago the results were very obvious... the head engineer at Ford nearly got blasted off the list serv (CPSPList) for daring to say that LATCH was far superior to seatbelts. I think he meant rigid LATCH.
Darren's got his 2 yo ff...in a rigid LATCH seat... ;)

Better order that Jane' Indy Plus before it disappears from the market... and if the Graco SS2 is so heavy, would it have mattered if they tossed an extra pound of rigid bars on it???

Anyway, I'm mad there's not more options and they are allowed to get away with the glorified lapbelts that we have here for LATCH...
 

stayinhomewithmy6

Senior Community Member
Anyway, I'm mad there's not more options and they are allowed to get away with the glorified lapbelts that we have here for LATCH...

What are the rigid LATCH options available right now. I know Britax used to have a seat with rigid LATCH, but that was a long time ago. The only other 1 I'm aware of is the Baby Trend LATCH Loc. Well, and the Jane Indy Plus, but I'm wondering specifically about harnessed seats.

Oh, and I came across this seat: Chicco Key 1 Isofix. Why doesn't Chicco make FF seats for the US?! I want one!
 

katiesmommy

Active member
Anyway, I'm mad there's not more options and they are allowed to get away with the glorified lapbelts that we have here for LATCH...

Agreed! Why don't they have rigid latch available on more seats. The LatchLoc is by far my favorite seat in general, mostly because of the isofix.
 

southpawboston

New member
but i'm also interested in why the 1" rule is considered "acceptable"??? that just seems absurd to me, given how much lateral movement a CRS can have in a side impact crash, even with the LATCH belt really tight. if the general concensus is that the less movement of the seat the better, then that 1" rule seems really "loose" (pun intended). i'm hoping some other techs can chime in on this issue.
 

singingpond

New member
but i'm also interested in why the 1" rule is considered "acceptable"??? that just seems absurd to me, given how much lateral movement a CRS can have in a side impact crash, even with the LATCH belt really tight. if the general concensus is that the less movement of the seat the better, then that 1" rule seems really "loose" (pun intended). i'm hoping some other techs can chime in on this issue.

And along the same lines, if really rigid attachment gives better crash results, wouldn't seatbelt plus LATCH (both used at the same time, with much less than 1" of movement) perhaps give better results in practice? I know we're always told not to do this, because it hasn't been tested, but what would happen if it actually were tested? (Assuming a vehicle where the LATCH points and the seatbelts are not so far offset that they're trying to place the carseat in different lateral positions on the vehicle seat during installation.) In general, is there evidence that a looser install is actually safer in some types of crashes than a really tight install? I've seen a couple of people say that the LATCH plus seatbelt install is bad because it holds the child restraint too tightly... which is a lot different than saying it is simply an untested configuration.

Katrin
 

southpawboston

New member
And along the same lines, if really rigid attachment gives better crash results, wouldn't seatbelt plus LATCH (both used at the same time, with much less than 1" of movement) perhaps give better results in practice? I know we're always told not to do this, because it hasn't been tested, but what would happen if it actually were tested? (Assuming a vehicle where the LATCH points and the seatbelts are not so far offset that they're trying to place the carseat in different lateral positions on the vehicle seat during installation.) In general, is there evidence that a looser install is actually safer in some types of crashes than a really tight install? I've seen a couple of people say that the LATCH plus seatbelt install is bad because it holds the child restraint too tightly... which is a lot different than saying it is simply an untested configuration.

Katrin

i agree. i didn't mention it because i don't want to promote an unsafe, unproven practice (LATCH + seatbelt). however, i do believe, despite what some have said about holding a restraint "too tightly", that having the restraint as immobilized to the car as possible is, in general, best. if there is any evidence that a seat performs better in a particular type of crash by having it "loose", i would like to see the actual data.

also keep in mind that this debate is all with respect to side impacts, i really don't know how the tightness applies to frontal crashes. again, maybe some experienced techs and/or instructors can chime in on both types of accidents and the benefits of immobile versus "loose" (non-rigid LATCH) seats.
 

CRS

Senior Community Member
Hell no I would NEVER use both LATCH and the seatbelt at the same time. Apart from it not being the "done" thing, against the manufacturers instructions and well, I believe DANGEROUS. You still need the seat to ride down in the crash, it still rides down with LATCH (rigid) apparently it pivots, now if you're going to use both it does make sense that one would impede on the other doing what it's supposed to do. Sorry just had to jump in there, no doubt a newbie would read it and think "hmm I should try that!". And as for the 1" of movement being allowable, I'm thankful for that for sure - you should see some of the seats here it would just be damn right impossible to install them so rigidly that the whole car shakes when you check it for movement. You also don't want parents getting upset when they can't install the seat so tight it doesn't move an itty bit. While some car seats might be able to be rigidly installed in some cars, it's not the same for all other cars and car seats.
 

CDNTech

Senior Community Member
i agree. i didn't mention it because i don't want to promote an unsafe, unproven practice (LATCH + seatbelt). however, i do believe, despite what some have said about holding a restraint "too tightly", that having the restraint as immobilized to the car as possible is, in general, best. if there is any evidence that a seat performs better in a particular type of crash by having it "loose", i would like to see the actual data.

also keep in mind that this debate is all with respect to side impacts, i really don't know how the tightness applies to frontal crashes. again, maybe some experienced techs and/or instructors can chime in on both types of accidents and the benefits of immobile versus "loose" (non-rigid LATCH) seats.

I like having the restraint as immobilized to the car as possible *but* only using one method.

I don't think the restraint is being held too tightly, especially for parents who mistakenly use both lower anchors and seatbelt, but that it is being held by two different methods.

Seatbelts and lower anchors do not secure identically and would put different strains on the child restraint in a collision... so it's not the fact that two methods are holding them in more tightly, but that they are holding them in differently.

I also don't think it's possible to get your install any tighter by using two methods. If you already have a rock the van solid install on a seatbelt install, the lower anchors are *not* going to make it any tighter and vice versa. ;)

I like the one inch rule for the simple fact that it makes more parents comfortable with being able to do their own installs. I do prefer a rock the car/van solid install though, *if possible*.
 

southpawboston

New member
i don't want to be misinterpreted here: i am *not* advocating using both LATCH and seatbelt simultaneously. i am advocating getting the seat tighter than the 1" rule! whether that be by cranking on that LATCH strap or seatbelt, playing with the seat angle, or going with a rigid LATCH mechanism, so be it. but if i let my seats move 1" with one arm (my weaker arm at that), something is seriously wrong IMHO.
 

singingpond

New member
Hell no I would NEVER use both LATCH and the seatbelt at the same time. Apart from it not being the "done" thing, against the manufacturers instructions and well, I believe DANGEROUS. You still need the seat to ride down in the crash, it still rides down with LATCH (rigid) apparently it pivots, now if you're going to use both it does make sense that one would impede on the other doing what it's supposed to do. Sorry just had to jump in there, no doubt a newbie would read it and think "hmm I should try that!". And as for the 1" of movement being allowable, I'm thankful for that for sure - you should see some of the seats here it would just be damn right impossible to install them so rigidly that the whole car shakes when you check it for movement. You also don't want parents getting upset when they can't install the seat so tight it doesn't move an itty bit. While some car seats might be able to be rigidly installed in some cars, it's not the same for all other cars and car seats.

Sorry I muddied the waters, and distracted attention from SPB's original question, by mentioning what is apparently a 'third rail' issue to some (i.e. LATCH plus seatbelt installation). My main question was whether there is any actual evidence that a very tight installation is ever less safe than an installation with 1" of movement. I would not install with both methods simultaneously, and I certainly didn't recommend doing it.... because it is untested, not because I somehow know that the two methods of attachment interfere with each other. Maybe they do interfere, maybe they don't, but how do we really know if it's untested. Frankly, I think it's silly to suggest that certain issues shouldn't be discussed, for fear that some hypothetical new reader will misinterpret a discussion as a recommendation. That's sort of insulting to the intelligence of the 'newbies'.

Katrin
 

singingpond

New member
I also don't think it's possible to get your install any tighter by using two methods. If you already have a rock the van solid install on a seatbelt install, the lower anchors are *not* going to make it any tighter and vice versa. ;)

I like the one inch rule for the simple fact that it makes more parents comfortable with being able to do their own installs. I do prefer a rock the car/van solid install though, *if possible*.

That makes a lot of sense -- i.e. that LATCH plus seatbelt combined may not actually give a tighter installation, so perhaps it isn't really relevant to the original discussion of rigid vs. loose installations.

Katrin
 

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