In response to Transport Canada's crash test footage and summaries

snowbird25ca said:

eta: Pixels is correct that the HE amount of 720mm in CMVSS 213 standards is the same as the top tethered amount in the FMVSS 213 standards. The difference is that US standards allow for 2 different head excursion numbers, and I believe the wording is actually such that if a seat didn't have a top tether at all it wouldn't be required to meet the 720mm #, rather only the higher # (900mm IIRC, but I'm not positive on that.) However, given that LATCH has been mandatory since Sept 2002, all seats in the US now have a top tether, meaning that all seats in the US must pass the 720mm head excursion limit when top tethered. So for all intents and purposes, from a numerical requirement point, top tethered seats in the US meet the same HE standard as ff'ing seats in Canada. There is just the double standard in the US which doesn't exist in Canada.

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If a US seat didn't have a top tether, it would still be held to 720 mm. The seat must meet the 720 mm standard when installed with a lap-only belt and "if a tether is provided, it is attached." Same with lower anchors only, and if a tether is provided, it is attached. The 813 mm standard is for lap-only belt and no tether attached, and for lower anchors only with no tether attached.

US seats are not required to have a tether, they just have to figure out a way to meet the 720 mm requirement. So far, no seat has done that (or at least has chosen not to provide a tether).

So this is probably me being confused... If the LATCH means having to use lower AND top anchors, then why the option of meeting HE requirement with lower anchors and no tether?

LATCH is an acronym that stands for both lower anchors and top tethers. But just like you don't have to use lower anchors in order to use the top tether, you don't have to use the top tether in order to use the lower anchors. Nobody thinks twice about using lower anchors without top tether for a rear facing seat. And not all seating positions with lower anchors have top tethers (namely some school buses and some convertibles). If the seat can perform just as well or better than the standard without the top tether, it doesn't need to be there just to be there.

That's how I understood that but a couple of times here on c-s.org, I was corrected otherwise (ie. LATCH must mean using lower and top anchors in the US) so I just took that as the 'standard'. But I hear ya

I have a few questions which may or may not be able to be answered here...
I've looked at only a few of the videos; for vehicles which are similar to ours (they didn't test with anything really close to the '94 Grand Am we'll be installing in) and for seats which are either what we have (Evenflo Embrace) or similar to what we're intending to get for later (Radian XT).

1. I understand that the rebound part of a crash is unlikely to cause severe injuries because of contact with a head rest and/or back of the seat back (soft surfaces). But there are some car seats that already have a RF tether - might be a dumb question but is there a list of these seats, and/or an explanation on how they work? After seeing the Embrace contact the back of the seat in a few of the vehicles (the one in the Honda Pilot was really scary, but I think that was more to do with the seat back moving due to a passenger behind it), I'm thinking that this could be a concern for us. We already have this seat so buying something else isn't really an option, but just looking for more info on the RF tethers.

2. I'm looking at these crashes and I don't see any (I didn't look at all of them) where the seat was installed in the middle position. Again on the rebound issue, could there be more of a concern if a RF seat is installed in the middle seat? Particularly in a vehicle like ours which doesn't have a head rest on the middle seat in the back? Though I know that the middle is the safest spot mostly because of side impact crashes, are frontal (either head-on or off-set) crashes more common and therefore the potential for a rebound injury potentially greater if the seat is positioned in the middle of a vehicle with no head rest? (For those who aren't familiar with this car, though this image is of a 2-door version - ours is 4 - you can see what might happen if a rebound popped the car-seat into the area of the head-rest in the middle seat: http://tinyurl.com/yj5en37) I'm sure I'm freaking out for (almost) nothing, but I would be very very upset if something as simple as putting the seat on one side or the other could potentially save a head injury due to a rebound - because from what I could tell when the Embrace contacted the seat back, it was the face of the dummy that hit the head rest - in our car in the middle that would be a padded area only the width of the seat and the potential to have the face contact the rigid shelf behind the seat.

3. I know they didn't test higher-weight RF seats, since they used an average 12 month old child dummy (anyone know what the actual weight of this dummy is?). So I'm wondering if they do any testing (even bench tests) on the higher weight RF seats, like for example a 30 lb dummy in the TF or MA or RN? Regardless, would these scenarios be more likely to result in a rebound injury? Even without the confusion about the seating angle, would a heavier child have more or less rebound? Should I be concerned about the potential for a rebound injury if we get the new Radian XT and use it as close to that 45 lb RF limit? (I'm aware of the fact that the regulations may change before we even buy this seat or before we get anywhere near the limits of it.) Or is there other things, like someone mentioned the potential for leg injuries in a larger child, which we should be aware of with a larger, higher weight child RF?

4. Finally, I don't expect that TC can realistically test every seat in every vehicle from even the last couple of years, but if they identify specific situations which are dangerous, and change the regulations, what will happen then? Like if they decide that certain RF seats should have a RF tether, will the manufacturers have to recall their seats and possibly replace them to have those regulations met? Or will they basically make an exception for seats that have been purchased before the regulations came into affect (or manufactured before that date)? What would happen if they identified that a certain seat in a certain vehicle needed something different, like a different tether or perhaps a seat-belt install instead of the LUAS? Would it be the car-seat manufacturer that had to change something or the vehicle manufacturer?

Sorry this is so long. I doubt that all of these can even be answered now or perhaps even by anyone here... but even opinions might help!

Thanks in advance,
Melissa

Pixels said:

If a US seat didn't have a top tether, it would still be held to 720 mm. The seat must meet the 720 mm standard when installed with a lap-only belt and "if a tether is provided, it is attached." Same with lower anchors only, and if a tether is provided, it is attached. The 813 mm standard is for lap-only belt and no tether attached, and for lower anchors only with no tether attached.

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So, is a seat that has a tether attached, ONLY tested to the 720mm standard? (i.e. only has to meet the 720mm standard because it has a tether) or are the seats tested both with AND without the tether? (i.e. meet the 720mm with the tether and have to meet the 813mm without).

TechnoGranola said:

So, is a seat that has a tether attached, ONLY tested to the 720mm standard? (and as such, only has to meet the 720mm standard because it has a tether) or are the seats tested both with AND without the tether? (and as such, meet the 720mm with the tether and have to meet the 813mm without).

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In the US, it has to pass both. It must pass the 720mm standard and can use a tether to do so (all current seats use a tether, I think the old FP seats are the only ones that ever did so without a tether). It also must pass the 813mm standard with just a lapbelt (or LA) and no top tether.

I understand that rebound looks really scary, but it's not. Injuries, when they happen, are minor, similar to a trip and fall on the sidewalk. Of course we never want to see our children injured at all, but if my child walks away from a severe accident with nothing more than a scraped chin or a black eye, I'm happy. Forward facing a child is more dangerous than the risk of rebound injury.

1. Only the Sunshine Kids Radians and Britax convertibles allow rear facing tethering. The True Fit Premier (which I'm not sure if it's available in Canada) has an anti-rebound bar that works differently but performs the same function. Some infant seats have an anti-rebound bar either on the base or on the seat, but I'm not sure which ones have it.

2. I think the 12 month old dummy is 20 pounds, maybe 22. In the same seat in the same vehicle, a heavier child would probably rebound more than a lighter child. Different seats or different vehicles would change the equation so I don't think you could make a prediction any more. You wouldn't have to worry about the risk of rebound injury with the RadianXT at/near 45 pounds because it can be tethered.

3. The way the laws are written, the manufacturers have to comply with them on the date of manufacture. If they change the law the next day, the "old" seat can still be sold, used, and will not be recalled as long as it complied with the law when it was manufactured.

4. With or without headrest, vehicles vary in height of the seat back, and crash dynamics and carseat installation method affect how high a seat rebounds. I don't think you can predict very well whether a child will rebound into the headrest or fly right over it, or just hit the seat back. At any rate, I'll say it again, risk of injury is very slight. Yes, frontal and frontal-offset crashes are the most common type. Side impact crashes are much less common, yet account for a much higher proportion of fatalities. Side impact crashes scare me more than a frontal impact does for the children in the back seat. (They both scare me for anyone in the front seat.) I absolutely would not move a child outboard for any perceived reduction in potential rebound injury. We KNOW that outboard is more dangerous. We know that rebound looks scary, but is mostly benign.

In the US, forward facing harnessed seats are tested in 4 configurations:
Lap belt only, no top tether, must meet the 813 mm requirement
Lower anchors only, no top tether, must meet the 813 mm requirement
Lap belt with top tether (if it has one), must meet the 720 mm requirement
Lower anchors with top tether (if it has one), must meet the 720 mm requirement

A seat that didn't have a top tether would only need to be tested twice to meet those 4 requirements, since passing the 720 mm requirement obviously is good enough to meet the 813 mm requirement.

Thanks Melissa - it helps at least to know that the seat we are considering after lo outgrows the Embrace does have tethers for RF. Now to figure out if we can actually install those tethers in the Grand Am (that's for another thread!).

I agree with you that I'd be ok if my lo 'walked' away from a severe crash with only a minor head injury, I'm just worried about the possibility of a rebound injury being more severe than just a black eye, especially in a vehicle like ours with no head-rest and a rigid shelf behind the seat. It sure would suck to have lo end up with a severe (or even moderate) head injury from rebounding into that shelf! I'm not thinking of going FF to avoid a rebound injury, just speculating on if there might be ways to prevent *any* rebound injury at all. I'm thinking that there probably isn't and it's still going to be better to risk the rebound with the Embrace (and figure out how to RF tether the Radian) in the middle position than to take the chance of a more severe injury from a side-impact in the outboard position.

The one thing that I do have to say though is that the whole car seat thing is CHALLENGING!!! There's so many seats and without the funds to buy multiple cars and seats to test them myself, it's brutally hard to decide which seat(s) to get!

But I think these videos are at the least helpful for convincing people to correctly install whatever seat they choose!

Thanks again,
Melissa

Pixels said:

You wouldn't have to worry about the risk of rebound injury with the RadianXT at/near 45 pounds because it can be tethered.
.

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We hope!

But didn't russ say in an email posted here somewhere that seats that RF to high weights do not have "standards" to meet? Do we know if the RF tether points would hold for a child that heavy?

Not saying rebound is "scary", but just saying, there may still be some rebound, or at least an unknown effect, of a RF 45lb child in a US seat, as it's not been done before.

I believe it's still likely safer than FF.

romanoma said:

We hope!

But didn't russ say in an email posted here somewhere that seats that RF to high weights do not have "standards" to meet? Do we know if the RF tether points would hold for a child that heavy?

Not saying rebound is "scary", but just saying, there may still be some rebound, or at least an unknown effect, of a RF 45lb child in a US seat, as it's not been done before.

I believe it's still likely safer than FF.

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Everything I'm about to say is based on US standards. I haven't even seen Canadian standards, though I believe they are largely based on US standards with some differences.

He said they do not have biomechanical testing requirements to meet over 22 pounds for rear facing, over 50 (IIRC) pounds forward facing. That means that they put the dummy in the seat, and test the seat, but it doesn't matter if the dummy has too much head excursion or if the Head Injury Criterion value is too high, they don't have limits. Basically they look to see if the carseat has any structural failures. I haven't looked carefully at the rear facing test requirements, but I know he is correct about forward facing.

As for whether the rear facing tether could hold a 45 pound child, I believe it will just like I believe it would hold an empty seat. Why? Because the company says it will. That's all we have to go on with rear facing tethers, because there is no testing of RFing tethers in the legal standards. The test bench doesn't have any place to attach a tether, and the law doesn't make allowance for it. When we use a RFing tether, we are trusting that the company has done their own testing and figured out whether it's safe.

It's a minor difference, but I mean the tether point (aka the anchor) for the RF tether. I agree, I believe the tether itself to be strong enough.

The only reason I question it is b/c these are makeshift anchors, not a standard part of the LATCH system, just a piece of metal under the seat that we hook our tether to. And as you say, there is no way to test them since they are not on the test bench.

All this is pretty off topic, but anyway, just wanted to clarify what I meant. I still say, we don't know what would happen in a bad accident to a 45lb RF child. I think the RF tether would still absorb a lot of the rebound forces even if the anchor didn't hold. But I also think they would experience more rebound than a younger child and possibly more injury due to the anchor failing under that much weight.

And thanks for the clarification on the testing requirements! :thumbsup:

Are you referring to the D-ring, which is used to create an anchor point, or to the piece of metal attached to the car, such as the vehicle seat leg, that we wrap the D-ring around?

I believe that the manufacturers test the D-rings. They can modify their own test benches to have a place to attach the D-ring.

As for the vehicle point, it's not tested (except for some very few vehicles that provide a dedicated RFing tether point) for this application. This is the basis of TC's resistance to RFing tethering. Personally, I'm confident that the point I chose will hold. If I wasn't confident, I wouldn't have used it because a tether hook coming loose and flying around does scare me.

Pixels said:

As for the vehicle point, it's not tested (except for some very few vehicles that provide a dedicated RFing tether point) for this application. This is the basis of TC's resistance to RFing tethering. Personally, I'm confident that the point I chose will hold. If I wasn't confident, I wouldn't have used it because a tether hook coming loose and flying around does scare me.

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Except that the TC resistance isn't just about the tether coming loose, it is about the effect of the forces being applied by the tether on the structure the tether is attached to. If attached to the seat track or to part of the seat, what will those forces do to the seat? The possibility of something bad happening with that front seat concerns me even more with a heavier child in the restraint. :twocents:

romanoma said:

It's a minor difference, but I mean the tether point (aka the anchor) for the RF tether. I agree, I believe the tether itself to be strong enough.

The only reason I question it is b/c these are makeshift anchors, not a standard part of the LATCH system, just a piece of metal under the seat that we hook our tether to. And as you say, there is no way to test them since they are not on the test bench.

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some carseat mfrs refuse to allow RF tethering for exactly this reason-- there is no such thing as a dedicated RF tether point, except in some swedish vehicles. they are all makeshift, and the end user has absolutely no idea how that tether point will hold in a crash. how can we as individuals be "confident" they will hold? on what basis can we make that judgment call? how is that any different from a DIY mom or dad using a home depot eye hook bolted into the floor as a retro-fit LATCH anchor and being "confident" that it will hold?

sparkyd said:

Except that the TC resistance isn't just about the tether coming loose, it is about the effect of the forces being applied by the tether on the structure the tether is attached to. If attached to the seat track or to part of the seat, what will those forces do to the seat? The possibility of something bad happening with that front seat concerns me even more with a heavier child in the restraint. :twocents:

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exactly.

Pixels said:

As for whether the rear facing tether could hold a 45 pound child, I believe it will just like I believe it would hold an empty seat. Why? Because the company says it will. That's all we have to go on with rear facing tethers, because there is no testing of RFing tethers in the legal standards. The test bench doesn't have any place to attach a tether, and the law doesn't make allowance for it. When we use a RFing tether, we are trusting that the company has done their own testing and figured out whether it's safe.

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but did the company test every possible RFTP in every car currently on the market?

Pixels said:

And in the United States at least, NHTSA (who has studied this extensively) and several manufacturers also say you don't always have to replace after every crash. But I agree, it would be interesting to see the performance difference (if any) between a pre-crashed seat and a new one.

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i forgot which company did this, but i remember one company did a series of tests on the same seat, and it continually performed well, even after repeated crash tests. i don't know if they replaced certain parts like the LATCH belt with each test, but the shell itself was retested and found to perform fine.

romanoma said:

We hope!

But didn't russ say in an email posted here somewhere that seats that RF to high weights do not have "standards" to meet? Do we know if the RF tether points would hold for a child that heavy?

Not saying rebound is "scary", but just saying, there may still be some rebound, or at least an unknown effect, of a RF 45lb child in a US seat, as it's not been done before.

I believe it's still likely safer than FF.

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I don´t think the rebounding would be an issue. It is the downward rotation in sideimpacts and frontal impacts that I would worry about. The Swedish seats have a long steel leg or a clamp that brace the seats towards the front alongside the tether straps and help prevent downward rotation.

Lena

Pixels said:

He said they do not have biomechanical testing requirements to meet over 22 pounds for rear facing, over 50 (IIRC) pounds forward facing. That means that they put the dummy in the seat, and test the seat, but it doesn't matter if the dummy has too much head excursion or if the Head Injury Criterion value is too high, they don't have limits. Basically they look to see if the carseat has any structural failures. I haven't looked carefully at the rear facing test requirements, but I know he is correct about forward facing.

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This disturbs me. Do you (or anyone else) know for sure if the manufacturers still hold their own seats to some internal standards? One would think they would, to reduce the risk of fatalities in their seats!!! (bad bad publicity, hehe) but is there any info on this?

SK has released some info on their internal testing. I would have to go back and find it ... but they released some new info when they released the SL seats. One thing that was interesting, they noted that the 85 pound dummy is too tall for the Radian, and because of that, did not meet the head excursion limit (I don't remember if it only did not meet without top tether, or if it did not meet with top tether as well). SK has stated that even though the law does not apply HIC, head excursion, and knee excursion limits above 50 pounds, they (internally) do require it, and the Radian (and Monterey?) meet those limits (with the exception noted above of head excursion with 85 pound, too-tall dummy).

In the US, the same limits (HIC, head excursion, knee excursion, whiplash protection) apply to all forward facing seats, whether it's a booster or a harnessed seat. The only difference is for tethered harnessed seats, head excursion is lower. Untethered head excursion has the same limit as booster head excursion.

I don't know about any other companies, though I certainly hope that they have internal standards.