just curious...booster as good as 5 point harness? [Archive] - Car Seat.Org - Carseat, Vehicle & Child Passenger Safety Forums

rjsmom35

04-19-2008, 12:05 AM

I have two car seats which go up to 65 pounds forward facing with the 5 point harness. I want my son in a 5 point harness as long as possible. We were going to get a seat that goes up to 80 pounds with a 5 point but I knew my son would not want to be in a "baby seat" for that long. I didn't want him to be teased or feel upset about it so we opted for the Britax Marathon for the van which we drive more often and the Apex 65 for the car. My ex also has the Apex 65 for when he takes my son for visits.

Well, a few months ago, I was at my mom's group and we had a female officer come in as a speaker and she talked about car seat safety. She said that as long as the child was in a booster correctly, that it was as safe as a car seat with a 5 point harness. In your opinion, would you say that was true? I find it hard to believe.

I am not going to change to a booster but I was just wondering what your opinions were on that. Thanks.

LCMOM

04-19-2008, 01:35 AM

Your officer was misinformed. Check out some of the crash test videos on boosters sometime; scary!! My mantra is always the most restraint is best; ERF, extended harness, long term booster, all make things safer. Lap and shoulder belts are developed for adults; small kids do not have the same bone density or muscle strength, so they need more help in terms of safety / restraint. Check out the Kyle David Miller foundation website; the foundation is in honor of a 3 year old who would have survived a crash in a 5 point, but died because he was in a booster.

joolsplus3

04-19-2008, 12:50 PM

At age 5 or 6, a kid is probably about as safe in a booster as a harnessed seat, statistically, if they can sit properly in it (and a highback booster is considerably safer than a no back, so use one as long as possible). And contrary to thinking kids get teased for being in a harness? My kids were harnessed mostly till age 7 or 8 and pitied kids who didn't get to ride in harnesses. They knew it was safest, and liked riding in them. Kids are smart, you can explain the facts to them and innoculate them against peer pressure (if they can be taught that doing the best thing now is the way to go, then they won't be so tempted to do the wrong thing when they are teenagers, I figure ;) )

emandbri

04-20-2008, 05:17 AM

Here are some crash test videos.

child in a booster
http://www.oeamtc.at/netautor/html_s...xicosirodi.mpg

dummy in a 5-point forward and beside one rear-facing
http://nz.youtube.com/watch?v=NMFPSS...eature=related

Adventuredad

04-20-2008, 05:34 AM

No, you officer was not misinformed. Or at least the issue is not as clear as it may appear on a video. I had posted a long reply here earlier but it got taken down for some reason.

Summary, the best child safety experts around, the Swedes, recommend instead using a booster seat. The reason is that the 5 pt. harness does keep a child in place but there is enormous pressure on the neck. In a booster seat the child moves more but this helps to protect delicate neck muscles. I have spoken to the people at the crash institute this week to clear up the issue and their recommendation is to use a good booster seat after rear facing regardless of country.

But the experts here add that both methods are safe. I have asked about testing to determine which is safer and gotten the answer that this is incredibly complex and difficult to do. It involves measuring too many points on a child's body and also determining importance of injuries etc.

The Swedes go from a RF set to booster seat at around 4 years of age and the safety record is phenomenal. A certain seat, booster or 5 pt. harness, might be preferred in certain situation but it's of course impossible crash situation (and when to crash) beforehand.

Joolsplus3 sums it up well I think.

Have a nice weekend

joolsplus3

04-20-2008, 09:03 AM

. I have spoken to the people at the crash institute this week to clear up the issue and their recommendation is to use a good booster seat after rear facing regardless of country.

But the experts here add that both methods are safe. I have asked about testing to determine which is safer and gotten the answer that this is incredibly complex and difficult to do. It involves measuring too many points on a child's body and also determining importance of injuries etc.

The Swedes go from a RF set to booster seat at around 4 years of age and the safety record is phenomenal. A certain seat, booster or 5 pt. harness, might be preferred in certain situation but it's of course impossible crash situation (and when to crash) beforehand.

Joolsplus3 sums it up well I think.

Have a nice weekend

Thanks :). I'll find something that shows that US kids are proving harnesses at older ages to be safe (ie, kids age 1-4, the standard harnessing age when heads are heavier and necks are weaker has been the standard of restraint here for decades with good record, and older kids being harnessed has not shown a spike of neck/head injuries... and the safety record provided by race car restraints is phenomenal, even at the high speeds they travel and crash, with a 5 pt harness).

southpawboston

04-20-2008, 10:26 PM

i have a study based on crash injury data from sweden, and there seems to be a slight jump in the injury rates when children transition from RF to booster.

i will try to dig up that study...

RJB78

04-20-2008, 10:52 PM

Is this the study you're referring to SPB?

ETA: My original link did not work, but I got it from this thread (post #22)

http://www.car-seat.org/showthread.php?t=13000&highlight=extended+harnessing+research

Trying original link again...

www-nrd.nhtsa.dot.gov/pdf/nrd-01/esv/esv19/05-0330-O.pdf

southpawboston

04-20-2008, 11:16 PM

yep, that's the one.

Adventuredad

04-21-2008, 01:18 AM

As I said above, both methods are certainly safe (and certified) which my friend at the institute pointed out to me. I'm not arguing that 5 pt. harnessing is bad or anything, I'm saying that it might not be as superior as it appears to be. You guys really know what you're talking about but some appear impressed by the nice harnessing without thinking further.

The greatest benefit with the 5 pt. method is also it's greatest weakness. The fact that all force is stopped by the chest and the neck is left to absorb tremendous pressure. It looks great on video but it's difficult to know what's really going on since there are too many things that are not measured (like the head). But I feel like many (perhaps not on this board) are fooled by how great it seems to handle crashes visually.

As a side note, I wish they would use test points in the head but tht's apparently not done. Today, Sweden follows the European ECE R44 E.U. standard but we also have our own standard (since the Swedes are boring and want to be extra safe:)) I really wish some of those ideas would be carried over to the current US and European standards.

The Swedish standard is (soon to be "was") called "T" and is stricter than the current ones but it being phased our because of EU. Think it will be gone by this summer. The older "T" standard was meant for kids 0.5-1 year to 3- 5 years. It was similar to todays US and EU standard but also had measuring points in the head. This basically meant that no FF seats got certified because it was simply too much pressure on the heads for the little kids. It's a shame testing of the head wasn't carried over. I'm unclear why that that didn't happen. I know the 5 pt. harnessed kids are often older but the head testing might have been interesting and informative regardless.

I might also mention some (weird) example my contact at the crash test facility made when we talked about 5 pt. harnessing and booster. He was talking about high jumpers in the Olympic Games trying to advance to the final. Limit is 185 cm. and 10 jumpers make it. Now, no one is asking how high over the bar competitors were. They are simply asking if they made it or not. That's the analogy he made. He mentioned that testing is done to see if seats make it or not but not by how much they make it. It could be barely or far better than required, that's irrelevant to them.

Thanks very much for the link, I'll take a look at it later.

joolsplus3

04-21-2008, 10:09 AM

So I've been researching a ton... I can't find a shred of real life evidence that harnessing is any 'less' safe than boostering. And the premier research organization that studies children in crashes recommends harnessing as long as possible

"http://www.prnewswire.com/cgi-bin/mi...TE=May+3,+2004 (http://www.prnewswire.com/cgi-bin/micro_stories.pl?ACCT=159681&TICK=CHOP&STORY=/www/story/05-03-2004/0002165781&EDATE=May+3,+2004)

"PCPS researchers note that the best protection for children aged 4
to 8 are either child safety seats with a harness or belt-positioning booster
seats -- depending on the child's size"

So I think what it comes down to is that we have to look at actual injury statistics, not dummy measurements. According to several carseat manufacturers in the US, seats should NOT be tethered rearfacing because it increases loads on the neck. That flies in the face of Swedish data, yes? Kids rearface tethered in Swedish seats are simply not getting neck injuries, and kids harnessed to higher weights and heights are not suffering head or chest injuries in this country.

To the OP, for ideal safety based on the data we have, keep your kiddo harnessed as long as they fit in the harness, and then get a booster seat that has very good side impact protection (a Highback Britax/Recaro/Maxi Cosi/Sunshine Kids/Compass B510...there are lots of choices!), and use a booster till your child is at least 4 foot 9 to 5 feet tall (usually about age 11 or 12)

:)

ProudMomof5

04-21-2008, 10:37 AM

So what about an older age/low weight child?
If all this is true about the force on the neck, does that get worse when the child gets older, or does it not matter.
For example, my dd is 6 1/2 and only 37 lbs... she sits correctly in a booster. I am planning on reharnessing her in a radian.. but now I feel confused.

From what I am reading, some say its more safe to harness, some say it isn't. Is there just not enough info? What should I do?

southpawboston

04-21-2008, 11:42 AM

As a side note, I wish they would use test points in the head but tht's apparently not done. Today, Sweden follows the European ECE R44 E.U. standard but we also have our own standard (since the Swedes are boring and want to be extra safe:)) I really wish some of those ideas would be carried over to the current US and European standards.

so are you saying that sweden is becoming less stringent now in adopting the ECE standard?

besides the head measurements in the "T" standard, how else did that standard differ from the ECE and FMV standards?

FWIW, more and more seats being sold in the US are also certified by ECE-44.04 standards. i know the basics of each test protocol but i know nothing about the T standard. i'd be interested to know other similarities/differences.

Adventuredad

04-21-2008, 01:06 PM

Joolsplus3, you're a superstar.;) I've been digging a bit as well since I think this is interesting stuff. Unfortunately day care called and I had to pick up my daughter and go the hospital since she had 104 fever....

I've talked to my friend at Volvo and tracked down one of the authors of the article which was discussed (www-nrd.nhtsa.dot.gov/pdf/nrd-01/esv/esv19/05-0330-O.pdf). I will be talking to her tomorrow for some more information. I also looked at the other thread (http://www.car-seat.org/showthread.php?t=13000&highlight=extended+harnessing+research)that discussed the article.

I usually need at least a bottle wine before my brains works well, and so far I've only had a couple of glasses, maybe that's why I fail to see any of the conclusions that were discussed.

"A tendency of higher injury risk was found
when the growing child switches from one
restraint to another, i.e. when the child is at the
youngest age approved for the restraint"

This is hardly surprising since the kids were switching from RF as I understand it. Nothing is safer than RF. And a younger kid is at higher risk regardless if it's in a 5 pt. harness or booster. That's physics and because of children's undeveloped bodies. To be seriously injured while rfing something extremely special must happen regardless of speed. I think the paper, once again, make a great case for RF until age 4 or so. When are people/organizations/professionals in other countries finally going to listen to this? I also thought it was nice to see the kids in Sweden are restrained 95% of the time. A good and high number.

The article mentioned doesn't even compare 5 pt. harnessing to anything, it's not even in the paper since it's not used here. So I find the paper interesting but not particularly relevant to the issue.

I've never heard that kids should not be tethered while rf. But I'm not an expert, and there are many things I don't know:). If it was better not to tether while rf, the Swedes would do it. I think the child accident stats for the country is very convincing. Especially since it's based of many years of reporting.There are extremely few kids dying in cars each year here and for a rf kid to die a truck must crush it or something like that.

I also don't see why there would be anything but minor differences between countries. It's kind of a secret dream for the people at the crash institute to get other countries, like US, to start using our rf chairs since it would save many lives.

The interesting thing with our discussion is that the reason 5 pt. supporters want people to use those seats, kids don't move much in a crash, is the same reason why experts here say it shouldn't be used. Isn't that kind of funny?:)

Your conclusion is very good Jools.(You got a PM yday by the way) But I couldn't open the link you included. Most important point to know is both methods are safe and certified. I find it far more important to make people ride rf until age 4 or so than convince them about benefits of booster of 5 pt. harnessing. The case for 5pt. harnessing looks so convincing, especially on video, and I think that's part of the reason why people are easy to dismiss the booster seats.

I will talk to the girl who wrote the report tomorrow, if she has time, and I will also find out more about the "T-standard". The issue about standard might not be very important but it's an interesting side point.

Correct me if I'm wrong , but age is more important that weight (as long as the seat is correct of course) concerning neck issues as someone asked. The neck does get stronger with age but it's impossible to say how much since this is individual. As I understand it, the muscles are only part of important factors. Ligaments and skeleton get stronger with age and are the important parts. Someone else can surely explain this better and far more accurate than me.

chickabiddy

04-21-2008, 01:14 PM

Correct me if I'm wrong , but age is more important that weight (as long as the seat is correct of course) concerning neck issues as someone asked. The neck does get stronger with age but it's impossible to say how much since this is individual. As I understand it, the muscles are only part of important factors. Ligaments and skeleton get stronger with age and are the important parts. Someone else can surely explain this better and far more accurate than me.

To some extent. I'd rather see a 38-pound 6-year-old in a booster than a 47-pound 2-year-old for sure, but I don't want to see a child under 35(ish) pounds in a booster regardless of age.

Adventuredad

04-21-2008, 02:08 PM

That was kind of my point which you got across a lot better.

o_mom

04-21-2008, 02:16 PM

As I said above, both methods are certainly safe (and certified) which my friend at the institute pointed out to me. I'm not arguing that 5 pt. harnessing is bad or anything, I'm saying that it might not be as superior as it appears to be. You guys really know what you're talking about but some appear impressed by the nice harnessing without thinking further.

The greatest benefit with the 5 pt. method is also it's greatest weakness. The fact that all force is stopped by the chest and the neck is left to absorb tremendous pressure. It looks great on video but it's difficult to know what's really going on since there are too many things that are not measured (like the head). But I feel like many (perhaps not on this board) are fooled by how great it seems to handle crashes visually.

As a side note, I wish they would use test points in the head but tht's apparently not done. Today, Sweden follows the European ECE R44 E.U. standard but we also have our own standard (since the Swedes are boring and want to be extra safe:)) I really wish some of those ideas would be carried over to the current US and European standards.

...

While the Swedish safety record is impressive, I don't think that it provides much data to support boosters being better or worse than 5 pt harnesses.

The US standard does include measurements of the head. The dummy has instruments in the head to measure acceleration. This is part of the Head Injury Criterion (HIC) in the crash test standard. If the head is under too much acceleration, the seat won't pass. I can't say how it compares to the Swedish standard, old or new, but it is measured.

There are also data from seatbelts around force limiting that show it isn't a clear cut issue. Force limiters were introduced on seatbelts to prevent injuries due to stopping too soon. They performed very well in crash tests and were installed in many cars. When the real-life data was examined, it was found that the reduction in injuries from sudden stopping were more than offset by increased injuries from striking the vehicle interior.

What I'm trying to say is that it is easy to look at a open test sled and say "let's increase the excusion to decrease the acceleration forces". In real life, however, we may find that the increase in head injuries would more than offset any decrease in spinal injuries for kids old enough to use a booster properly.

I also feel that it comes back to a properly used seat being safer than a misused seat. I routine drive a 5yo and 7 yo in boosters (parents' choice). At least 80% of the time when I look back they are sitting wrong - belt off the shoulder, slouching, etc. This is with constant reminding - they just don't have that level of development yet. If they fall asleep is is even worse. I have yet to meet a child under 6 that was capable of sitting correctly the entire ride every ride. Heck *I* have a hard time sitting correctly all the time when I am a passenger. With a properly used 5 pt harness, I don't have to rely on the impluse control of a preschooler to keep them safe.

BookMama

04-21-2008, 02:25 PM

I also feel that it comes back to a properly used seat being safer than a misused seat. I routine drive a 5yo and 7 yo in boosters (parents' choice). At least 80% of the time when I look back they are sitting wrong - belt off the shoulder, slouching, etc. This is with constant reminding - they just don't have that level of development yet. If they fall asleep is is even worse. I have yet to meet a child under 6 that was capable of sitting correctly the entire ride every ride. Heck *I* have a hard time sitting correctly all the time when I am a passenger. With a properly used 5 pt harness, I don't have to rely on the impluse control of a preschooler to keep them safe.

To me - barring any truly conclusive date, which we obviously don't have - this is the #1 reason for keeping kids aged 4+ harnessed.

In fact, this is a big part of the reason that I agreed to my 7YO's recent request for a harnessed seat in our secondary car. He mainly rides in that car when I pick him and DD up from school/preschool - they are always happy to see each other at the end of the day, and I often seem him reaching over to touch her hand, give her a book, share a toy with her, and I constantly find myself saying "DS, please sit back in your booster." And this is the well-behaved, non-fidgety, safety-conscious son of a tech. I know that most kids don't sit in a booster as well as he does.

Stretchy Glue

04-21-2008, 02:29 PM

To me - barring any truly conclusive date, which we obviously don't have - this is the #1 reason for keeping kids aged 4+ harnessed.

In fact, this is a big part of the reason that I agreed to my 7YO's recent request for a harnessed seat in our secondary car. He mainly rides in that car when I pick him and DD up from school/preschool - they are always happy to see each other at the end of the day, and I often seem him reaching over to touch her hand, give her a book, share a toy with her, and I constantly find myself saying "DS, please sit back in your booster." And this is the well-behaved, non-fidgety, safety-conscious son of a tech. I know that most kids don't sit in a booster as well as he does.

I am fortunate to have a dd that has always been a good car rider, but I've always been very anal about how she is sitting. When I had to switch her to a booster earlier than I wanted, she did fine, but I find that unless the parent is VERY diligent in reminding and enforcing children to sit properly, they just aren't ready until closer to 6 (in my experience). If it is finacially practical, I always suggest a HWH seat for kids under 5. If I do have to put a younger child in a booster, I make a point of emphasizing to the parents how critical it is to watch this.

BookMama

04-21-2008, 02:33 PM

I am fortunate to have a dd that has always been a good car rider, but I've always been very anal about how she is sitting. When I had to switch her to a booster earlier than I wanted, she did fine, but I find that unless the parent is VERY diligent in reminding and enforcing children to sit properly, they just aren't ready until closer to 6 (in my experience). If it is finacially practical, I always suggest a HWH seat for kids under 5. If I do have to put a younger child in a booster, I make a point of emphasizing to the parents how critical it is to watch this.

DS is actually an excellent car rider, it just happens that almost the only time he rides in a booster is the also the only time he is so distracted. He and DD are just so crazy about each other and happy to see each other at the end of the day. :love: He does great on the days that I have only him, when DH picks up DD. :thumbsup:

SingleMomTo2Girls

04-21-2008, 03:11 PM

I am also very fortunate to have absolutely wonderful children as long as we are in the car. They have been able to unbuckle themselves for months now but they NEVER do it without asking. Even if we have been parked for 30 minutes, watching airplanes at the airport...they still say "Mom, can I get out of my seat now?" :love:

I have absolutely no doubt that they would both do wonderfully in a booster. That doesn't mean I'm going to put them in it. In MY (non tech) opinion it is a step down in safety.

Rear facing is safest (which they did full time until they hit 35lbs at 3 and 4 years old.)

Forward facing with a harness is the next safest (which they will do until they outgrow the Regents.)

After that a booster with side impact protection until they outgrow that.

I will keep them in the safest seat I can, for the longest time that I can. :thumbsup:

As far as the harnessed vs booster discussion... My oldest daughter has an instability in her neck and we see a Neurosurgeon for that. We had set up a meeting to talk to him in person for the first time and it was about a week away on a Thursday. I had told him on the phone that I go up by his hospital every Saturday to see Grandparents. The Saturday before our appointment I got a call at 5pm from his nurse. She was letting me know that he had been called in for emergency surgery and would be done around 7pm. If we wanted to stop by and meet him at the hospital we could. :eek:

Of course we met him up there that night. I actually talked to her Neurosurgeon about car seats. He brought it up and asked me how she rode in the car. :love: I told him she was in the Regent and he knew what it was. He explained that he brought it up because his emergency surgery was an 18 month old child who was forward facing. Their neck was broken in a head on car accident. Everyone else was not as seriously injured.

He said that many of his surgeries are children who were not as well restrained as they could be. Forward facing too soon, or not installed tight enough and hitting the seat in front of them, things like that.

I did also ask him about the booster/vs forward facing thing. Since the concern with my daughter would be forward strain on the neck, such as touching your chin to your chest. I was concerned that being in the harness might actually end up contributing to a serious injury in an accident. I did ask him if a booster would allow her neck more flexibility as to not be quite as likely to break in an accident.

He told me that he would be just as if not more concerned about her hitting the seat in front of her if she was in a booster. We talked about how in the accidents where we would be concerned about Ali... likely her head would go forward and down anyway. In a booster her head would likely go forward and down, then she would hit the seat in front of her and it would compress it even further down. (We drive a truck so the seat in front of her is also closer than it might otherwise be.)

In a harness, yes her head would still go down towards her chest but there wouldn't be anything else to push it down further. She wouldn't be likely to impact anything like she would in a booster.

He said if she was his child he would still go with the absolutely overall safest option, which is harnessing. I don't know whether that helps at all, but I agreed with him. It was a different perspective to talk to a doctor who fixes these types of injuries... as well as being so knowledgable about car seats.

I feel more comfortable with them harnessed. I don't have to worry about that "what if" they move just as we get in an accident. I know without a doubt that they are in their seats and sitting correctly at any given moment. :thumbsup:

I am fortunate to have a dd that has always been a good car rider, but I've always been very anal about how she is sitting. When I had to switch her to a booster earlier than I wanted, she did fine, but I find that unless the parent is VERY diligent in reminding and enforcing children to sit properly, they just aren't ready until closer to 6 (in my experience). If it is finacially practical, I always suggest a HWH seat for kids under 5. If I do have to put a younger child in a booster, I make a point of emphasizing to the parents how critical it is to watch this.

Adventuredad

04-21-2008, 03:20 PM

Very good points about the sitting position. I agree that this is important. I'm not sure if my son is weird but he sits perfectly in his booster despite having turned around just recently.

About the crash tests. According to what I can find, ECE R 44 does not include any measuring points in the head. I've asked specifically about differences between ECE and FMV and gotten the reply they are very similar. Slightly different seats and sled, etc. IMHO, the US crash test would be better if measuring head trauma as well but perhaps there are some things about it that explain it all. I need to find out more info.

The older Swedish T standard together with the ECE is supposed to be the strictest test around. I have some more info about the differences regarding T standard and ECE and will post that tomorrow.

Adventuredad

04-21-2008, 03:24 PM

SingleMomto2Girls: Thanks for asking about that and posting about it. I think those kind of opinions are very valuable. And horrible to hear about the 18 month old:mad:

SingleMomTo2Girls

04-22-2008, 05:51 PM

SingleMomto2Girls: Thanks for asking about that and posting about it. I think those kind of opinions are very valuable. And horrible to hear about the 18 month old:mad:

I nearly fell off my chair when he said, "Alright, now how does she ride in the car?" I had never been asked that before by a doctor, I was totally shocked. When he actually knew what he was talking about I was even more shocked. He even went as far as letting Ali show him her seat (after he asked she was all excited about showing it off. lol) He's really a great guy, great doctor and he loves what he does.

He said that he does a pediatric car accident related, preventable surgery about once a week on average. There are more that he isn't sure are preventable... but he gets at least one a week that is still small enough to RF but wasn't or that was poorly restrained. Now granted they bring people down here from Idaho and other states too...but that's still way too many. He said if everyone was as neurotic about car seats as I am, his patients would probably be cut in half!

The Neurosurgeon is in my top 3 favorite dr's...and that's saying a lot. :thumbsup:

(Oh, and that particular 18 month old got very lucky. At our follow up appointment I asked and he said the baby is doing better than expected. Even though the neck was broken it looks like they will be able to walk again eventually. After the 6 months in a halo anyways.)

thrillhouse

04-22-2008, 10:06 PM

I read a lot of this thread but not all...forgive me if I'm way off topic now :)

In canada we do test the head movement. That is why ALL ffing harnessed seats must be tethered. it greatly reduces head excursion. I'm comfortable keeping my 4.5 yo in his radian for another year or two as long as he fits and is comfortable. We should also keep in mind that the harness in a child seat is designed to stretch in a crash, to ease the load and pressure. it's not like the body is stopped by steel bars and the head keeps on going.

Adventuredad

04-23-2008, 12:39 AM

SingleMomTo2Girls:Isn't it fantastic when a doctor combines his great "doctor skills" with practical experience as well? In your case, it must be invaluable for the doctor to be able to talk about car sets and make recommendations while combining this with his expertise as a specialist doctor. Combining car seat knowledge with the authority of a doctor is a IMHO a great way of making impact on parents. It's a person people will really listen to.

Glad to hear about the 18 month old, kills me just to hear about it.

o_mom

04-23-2008, 07:59 AM

thrillhouse

04-23-2008, 03:22 PM

I think Adventuredad was talking about measuring acceleration of the head in someway, not just head excursion. In the US it is part of the Head Injury Criterion (HIC). I'm not sure what Canada does.

right, and wouldn't those be directly related? in any case, using the tether ffing is a good idea :)

o_mom

04-23-2008, 03:32 PM

right, and wouldn't those be directly related? in any case, using the tether ffing is a good idea :)

Not necessarily :) Head excursion just measures how far the head moves from some fixed reference point. The HIC looks at the peak time of acceleration of the head and measures the forces over a period of time around that peak. That's a huge simplification of it, but you get the idea. A seat could have very low head excursion numbers but high HIC because it stops the head so quickly. This doesn't always happen, though and top tethers seem to reduce BOTH excursion and HIC, just looking at the US compliance data. Some seats have very low head excursion along with low HIC, but others do not, so it is not a 1:1 correspondance. I have no idea what Canada does, but it appears the the EU standard only measures head excursion.

CRS

04-23-2008, 07:21 PM

SO I guess it's about weighing up the "pros vs cons" do I a) want more "forces" on my childs neck or b) put them at higher risk of having their heads smack in to the seat in front of them? I know that in my vehicle, I certainly do not have much room, so I'd probably be more inclined to have them harnessed past 40lbs to be honest. And I'm sure that when they do these tests such as the Swedish has (and this is not to say they're wrong about the "forces" on the neck, they probably are right for all I know) my guess is that they do it on a sled test with NOTHING in front of the dummy - and the reality is that in most vehicles there IS something in front of the child, be it a seat, or whatever and usually they're within close proximity to it. Hope that makes sense? In this case, given both "sides" I'd surely make an educated and informed decision to use a harnessed and tethered seat for as long as possible :twocents:

Adventuredad

04-24-2008, 02:04 AM

That's a pretty good summary. The Swedish test are in reality very similar to the US crash testing. It's actually European crash testing, ECE R 44 I've asked for a little more clarification of how they if/how they measure impact on the head and still waiting for that. The only difference earlier was our "T" standard which did measure more points in the head on seats up to 3-5 years (before boosters or extended harnessing) and in this case it was impossible for a ff seat to be certified. But that's not applicable here since we're talking about two ff seats.

I don't know what car you have but if my son is to hit the front seat in our Volvo, something must go extremely wrong. He must basically be sitting without his seatbelt. Otherwise he moves but is not close to the front seat.

I wish we had more data on this, it's a very interesting discussion. I think part of the problem with booster seats is that many (irresponsible) parents use ONLY the bottom part of the seat, not the top which means the seatbelt is in totally wrong position. I've seen parents here (foreigners) who put their daughter ff at 24 months in a backless booster. They think that's great protection.:eek:

I'll try to find out more information but there seems to be little hardcore data regarding this comparison. I've got a meeting set up this afternoon with a safety expert at Volvo and will run this by her to see what she says.

CRS

04-24-2008, 05:40 AM

Someone mentioned the "T" standard earlier... and Sweden changing to the ECE R44... I asked someone I know about this and they said from next month the new rules are that a child restraint is only allowed to display one standard, ie not both ECE and T like most Swedish seats do. Due to the T- standard not being known or recognised in many countries most Swedish seat manufacturers are likely to choose the ECE standard. They will still be testing to the T-standard for obvious reasons, but they won't be allowed to display that on the seat if it also says ECE! Does that make sense?

CRS

04-24-2008, 05:42 AM

I don't know what car you have but if my son is to hit the front seat in our Volvo, something must go extremely wrong. He must basically be sitting without his seatbelt. Otherwise he moves but is not close to the front seat....

Well, who knows, when my children go from rear-facing to forward-facing I may well put them in the best belt positioning booster money can buy, (so likely I will have to import one from europe!!!!). The reality is that I have at least two years probably until I have to make this decision so I might change my mind and have them in a booster rather then a harnessed seat. No doubt between now and then there will be more research on what truly is best and I will probably have a new car anyway where I will be quite happy for them to be in booster seats. Who knows what the future will hold really.

joolsplus3

04-24-2008, 07:19 AM

Well, who knows, when my children go from rear-facing to forward-facing I may well put them in the best belt positioning booster money can buy, (so likely I will have to import one from europe!!!!). The reality is that I have at least two years probably until I have to make this decision so I might change my mind and have them in a booster rather then a harnessed seat. No doubt between now and then there will be more research on what truly is best and I will probably have a new car anyway where I will be quite happy for them to be in booster seats. Who knows what the future will hold really.

And cool news from the LATCH manual is that top tethered seats not only reduce head excursion but also reduce neck forces :). Makes me wonder if any of these Swedish tests ever used top tether anchors...?

CRS

04-24-2008, 07:25 AM

And cool news from the LATCH manual is that top tethered seats not only reduce head excursion but also reduce neck forces :). Makes me wonder if any of these Swedish tests ever used top tether anchors...?

I struggle to fathom how they REDUCE neck forces? What page is it in the LATCH manual? Oh not that I don't believe you - I want to know about this type of stuff!

joolsplus3

04-24-2008, 07:33 AM

I know, I need to take more physics to understand it, but here 'tis (Thanks to Wendy for typing it up):

In the 2007 LATCH manual, page 43 it says this.
"Can a tether cause neck injury?
After many years of experience in Australia, Canada, and, now, the US,
there has been no evidence of neck injury related to the use of a
tether. In fact, a Canadian study(1) showed that all measurements
relating to potential neck injury were lower with a tether than without
it. This is because the tether secures the CR--and the child--more
tightly to the vehicle, allowing the child's body to "ride down" the
crash with the vehicle as it crushes and absorbs crash energy. Without
a tether, there may be more potential of higher forces on the neck when
the CR suddenly stops moving forward."

Adventuredad

04-24-2008, 08:00 AM

Someone asked the other day about the "T" standard and I have some more info. This ties into the whole discussion about booster and 5 pt. harness, a very interesting and educational discussion IMHO. We talked about ECE R 44 (Europe) and FMVSS 213 (US) and if they are the same.

There are similarities and differences between ECE R44, VVFS 2003:29 ("T" standard), and FMVSS 213 but it's not possible to say that one is better than the other. Basically, as someone mentioned earlier, in FMVSS 213 head is measured while it's not in ECE R 44. It is measured in the Swedish "T" standard. But it's not as simple as that.

In "T" (from now known as simply T because it takes too long to write....) all three directions of acceleration are measured. X, Y, and Z. These are used to calculate the resultant which should have an upper limit less than 500 m/s2. There is also an upper limit of Z which is 200 m/s2.

In FMVSS all three directions of acceleration are measured. These are used to calculate HIC (Head Injury Criteria) which has an upper limit of 1000 but there are no upper limits for Z acceleration or resultant.

In ECE R 44 there is no measuring of the head but all three directions of acceleration are measured in the chest. These are viewed as a good measure of what happens in the head, especially when it comes to Z acceleration. Experts say that Z acceleration in chest and head are more or less the same, therefore an upper limit of 30 G has been set in a positive direction (according to SAE 211). Some differences between this test and "T" are that the seats are crash tested from behind and also turned upside down in ECE R 44 and not in T. I also believe the fabric certification (material) is stricter (not sure about this last point)

Whatever standard is used, experts only looks at pass or fail. Not at how high over the limit a seat is. If one should figure out if a booster or a 5 pt. harness is better, one must measure them side by side. This would mean experts first agreeing on WHAT should be measures and what measures should be important. Lets say we want to measure HIC, then we need to do two identical tests with 5 pt. harness and booster. This would (hopefully) clear up what would be better (depending on terms set ahead of test) in this specific crash situation under these special circumstances.

It would not be enough with one test like this. A lot of different test would have to be made and compared side by side. Also, not to forget, experts would have to agree on what's the most important factors and place them on some kind of scale. For example, would a broken neck be better than a broken back? How much movement in the car by a booster would be good and what would be dangerous? Etc, etc. It would be somewhat subjective criteria which might vary depending on country/experts.

The T standard "expires" in May 2008 because countries which are in EU are not allowed to have national rules that are different than EU's rules.

One of the most common questions crash testing experts are asked are which testing method is "best". As one reads more in depth about the tests, it's clear that this is more or less impossible to answer.

Having a car seat certified by T and ECE R44 is supposedly the strictest standard but I'm sure there are people or experts who disagree. Seems like most experts agree on on disagreeing in some areas. I've also noticed that the deeper one digs the more factors pop up that are important and might be read and interpreted differently.

That's a short (yeah right) summary of the different tests. Now, if you managed to stay awake and read all this, I will buy a you a round of drinks;)

Adventuredad

04-24-2008, 08:02 AM

Jools: I read that same paragraph and thought it made sense

o_mom

04-24-2008, 08:12 AM

Thank you for that info on the testing!

I think we need to also keep in mind that even with all this testing, it is the real-world performance that matters in the end. :)

Adventuredad

04-24-2008, 08:15 AM

o_mom: Good point, I think we kind of forget that at times....

CRS

04-24-2008, 08:24 AM

In "T" (from now known as simply T because it takes too long to write....) all three directions of acceleration are measured. X, Y, and Z. These are used to calculate the resultant which should have an upper limit less than 500 m/s2. There is also an upper limit of Z which is 200 m/s2.

And what does that mean in english? LOL. Maybe I'm tired (it's 12:30am here) but all that says to me is "blah blah blah". If you have the time, can you explain what that is?

Adventuredad

04-24-2008, 08:34 AM

Oh no, follow up questions. My nightmare:D I'll try to put something together later. Go to bed;) Don't you ever sleep, you're on this board 24/7......

Adventuredad

04-24-2008, 08:58 AM

I'm enclosing a picture which might be helpful. I'm not sure if every test is the same: Positive X-axis from neck to nose, y-axis positive from left to right, and Z-axis positive direction downwards.

It's basically acceleration in different directions which is interesting from a crash perspective since high levels can be spotted in test dummies. There are certain levels that should not be exceeded, I 'm assuming these levels come from real situations and empirical testing in labs.

skaterbabscpst

04-24-2008, 09:24 AM

Oh no, follow up questions. My nightmare:D I'll try to put something together later. Go to bed;) Don't you ever sleep, you're on this board 24/7......

;) She's in New Zealand, so her time is several hours off ours. ;)

southpawboston

04-24-2008, 10:24 AM

thank you adventuredad, you answered my question about the difference in T and ECE standards very nicely! :thumbsup:

it has long been held here that the safest choices in cars are those that perform well in different crash tests, because, as you say, it is hard to say that one is better than another; rather, they can be complimentary since they cover different criteria. however, that thought has not been endorsed here with regard to carseats because most carseats sold in the US pass only FMVSS213. so techs are taught to believe that all seats sold in the US are equally safe (provided they are used correctly and fit both the car and child well).

that said, i can see why a seat that passes both the T and ECE standards would be a "better" pick. since T is set to expire this year, would you say that the "safest" seats henceforth would be those that pass both FMVSS213 and ECE-44? because it is possible to legally purchase and use seats in the US that pass both standards... there aren't many, but there are a few.

BookMama

04-24-2008, 10:33 AM

so techs are taught to believe that all seats sold in the US are equally safe (provided they are used correctly and fit both the car and child well).

That's not entirely accurate. :) We're taught that all seats sold in the U.S. are safe. Are some seats more safe than others? Sure, probably! But because we're not privy to the testing that manufacturers do, we don't know for sure how much safer they are and why they are safer. And it's bad to suggest to parents that the seat they have (maybe the only one they can afford) may not be as safe for their child as another seat, even when used correctly, because they will take that to mean that their child is UNsafe in the seat they have chosen. I have some specific comparisons in mind but will refrain from stating them for that reason.

:twocents:

Adventuredad

04-24-2008, 11:17 AM

Very good points. Theoretically, passing both "T" and ECE R 44 might be considered "better". But it's not as simple as that. There are seats that could be certified as both T and ECE R 44 but are not. This might be of financial reasons or perhaps the manufacturer thinks it's not necessary. Some might think it's overkill. After all, how many parents are going to ask for both T and ECE R 44? I know many on this board might but face it, you guys are into car seat porn and slightly nuts:D I don't know how much a certification costs but I don't think it's peanuts.....

Personally, I wouldn't care much if it passed both ECE R 44 and FMVSS 213 since they are very similar. And both safe IMHO. I do care a lot about the rear facing issue. Making kids rear facing longer seems like an "easier" way of saving many lives without adding lots of cost.