Head excursion for little FFers

Pixels · Feb 6, 2009

OK, I've been thinking about this a lot lately. I often see one seat recommended over another seat for little FFers because of the low head excursion numbers, or to make sure that it's tethered. But that just doesn't make sense to me.

The purpose of limiting head excursion is to (hopefully) prevent the child's head from striking the interior of the vehicle. It has no direct bearing on neck loading that I can see. The way that it's measured, it does not indicate the total distance that the head traveled in the crash.

In fact, might it not be better if the head traveled farther? Thus increasing ride-down time and decreasing neck loads. In fact, this is what the SafeStop on the Radian does. It allows the head to travel farther, increasing ride down time and decreasing neck loads.

Of course, it's difficult to compare apples to bananas (or Radians to Marathons) with the testing the way that it is currently done. If the Radian was the exact same seat, but the shell was 2 inches thicker behind the child's back, the head would start out 2 inches farther forward, travel the same distance (and presumably have the same neck loading characteristics), and have a higher head excursion number (by 2 inches) just because it started out farther forward.

I believe the HIC number is a more accurate (though indirect) indicator of neck loading. It is derived from the acceleration forces measured in the test dummy's head. Lower acceleration (which means reduced forces) results in lower HIC numbers.

Make sense?

canadiangie · Feb 6, 2009

I recommend the Radian for young ff's b/c of the SafeStop.

fyrfightermomma · Feb 6, 2009

pixels99 said:
In fact, this is what the SafeStop on the Radian does. It allows the head to travel farther, increasing ride down time and decreasing neck loads.

That's the precise reason that seat is recommended for younger lighter FFers

Not so much the head excursion numbers, but the lower neck loads from the safe stop

scatterbunny · Feb 6, 2009

fyrfightermomma said:
That's the precise reason that seat is recommended for younger lighter FFers Not so much the head excursion numbers, but the lower neck loads from the safe stop

:yeahthat: I usually recommend the Radian for that reason for young FFers, OR I recommend any convertible that has some natural recline and side wings fairly close to the body (for comfort/head support for those young ones), like the Britax convertibles.

joolsplus3 · Feb 6, 2009

I prefer to see young FFers in a seat with increased ride down and better side impact protection. Radian with the Safestop, Britax with the Rip Stitch tether...any seat with good SIP (because the latest study showed a not-even-statistically-significant difference in kids in frontal crashes FF, but a HUGE difference for FF kids in side impacts).

joolsplus3 · Feb 6, 2009

But in reality, I sell seats to people every day who I know will not install them properly or use the harness tight enough, and the 10 seconds I have to educate them about proper use includes 'read the manual, and use the top tether strap'. Top tethers have prevented loads of injuries in Canada and Australia over the decades, even with babies turned very young, so I doubt they contribute significantly to carseat injury rates, kwim?

Edit...ps...sorry for the serial posting, I just thought the ivory tower versus the harsh reality dichotomy was interesting

TechnoGranola · Feb 6, 2009

Does the method of install in Europe reduce head excursion? (i.e. don't they use the shoulder belt as part of the install rather than just lumping it together with the lap portion like we do in NA?). Is it as effective as a top tether? If it was, I like that it's not an extra piece to the install and that it wouldn't have weight restrictions like top tethers.

joolsplus3 · Feb 6, 2009

The crash tests I've found on youtube don't seem to be too much different between that lockoff and a top tether...but I don't know all the specifics...it's definitely nice not to have extra bits and pieces, though :thumbsup:

Kat_Momof3 · Feb 6, 2009

but I believe they also got rid of those evil 2-point seatbelts we still have had stuck in our vehicles until this year.

a top tether was a faster and retroactive type fix for reducing head excursion and all than making lockoffs like those standard, which would not only require redesigning the seats from all manufacturers, but also require shoulderbelts that wouldn't always be there.

TechnoGranola · Feb 6, 2009

Kat_Momof3 said:
but I believe they also got rid of those evil 2-point seatbelts we still have had stuck in our vehicles until this year.

a top tether was a faster and retroactive type fix for reducing head excursion and all than making lockoffs like those standard, which would not only require redesigning the seats from all manufacturers, but also require shoulderbelts that wouldn't always be there.

I guess I still don't get it. Vehicles I've owned vehicles with rear shoulder belts since '91. You're telling me that vehicles have had lap belts until 2009?

I'm not arguing that the top tether isn't beneficial, but seriously, to focus on a solution that existed for lap belts, is ridiculous at this point. Especially since there are other countries to use as examples. Design the restraint to work with the shoulder belts ALREADY IN THE VEHICLE and for a tether if you don't have a shoulder belt (if that's necessary. I don't know the stats of those having lap belts only.) Quit adding design work and cost to the vehicle manufacturers to add in lower anchors and top tethers that people don't use properly and focus on using the restraint system that already exists in vehicles. Seriously, wasting time and money designing an anchor system that holds a 40/48 pound child when a seat belt is designed to hold, what is it? 600 lbs? And then implying LATCH is superior? (like recent NHTSA ads do), COME ON!

Pixels · Feb 6, 2009

The purpose of LATCH was supposed to make installations easier and more uniform among vehicles, thereby reducing installation errors and problems. Unfortunately, it just seriously complicated things.

TechnoGranola · Feb 6, 2009

pixels99 said:
The purpose of LATCH was supposed to make installations easier and more uniform among vehicles, thereby reducing installation errors and problems. Unfortunately, it just seriously complicated things.

I completely agree. Use what you have and what people are familiar with instead of introducing something new.

scatterbunny · Feb 6, 2009

Many folks still drive 80-something vehicles. Not everyone is rich enough to own something with shoulder belts in the back. Also, until VERY recently, shoulder belts were only available in outboard seating locations, and it's been drilled into everyone's head how much safer the center is. AND, FMVSS says seats must pass testing installed only with a lap belt, so that's how they are designed here.

TechnoGranola · Feb 6, 2009

scatterbunny said:
Many folks still drive 80-something vehicles. Not everyone is rich enough to own something with shoulder belts in the back. Also, until VERY recently, shoulder belts were only available in outboard seating locations, and it's been drilled into everyone's head how much safer the center is. AND, FMVSS says seats must pass testing installed only with a lap belt, so that's how they are designed here.

Rich enough? That's hilarious. I paid $2000 for my pathetic 1991 Ford Escort in 1998 (I say pathetic because I wasn't into a boring wagon with a tape deck at the time). My dad sold it in excellent working condition (new tranny, new CV joints, new tires) in 2005 for $500. You definitely don't have to be rich to have a vehicle with shoulder belts. Heck, and that's Canadian dollars. And I was single mom, going to University, with no job income, so it's not like I was made of money when I picked up that fancy wagon. And it only had shoulder belts outboard. I kept her harnessed until 40 pounds (highest weight seat at the time) and then moved her high back booster outboard.

I'm not here to argue, I am just annoyed that this is how things are dealt with here. So, I do get your points, I am just irked, annoyed, bothered by the system! (not annoyed by your comments at all!)

scatterbunny · Feb 6, 2009

TechnoGranola said:
Rich enough? That's hilarious. I paid $2000 for my pathetic 1991 Ford Escort in 1998 (I say pathetic because I wasn't into a boring wagon with a tape deck at the time). My dad sold it in excellent working condition (new tranny, new CV joints, new tires) in 2005 for $500. You definitely don't have to be rich to have a vehicle with shoulder belts. Heck, and that's Canadian dollars.

That was said a bit tongue-in-cheek. I suppose I should have included a smilie or something.

Still, these old vehicles ARE still on the road. My dh drives one of them. My best friend drives another.

TechnoGranola · Feb 6, 2009

scatterbunny said:
That was said a bit tongue-in-cheek. I suppose I should have included a smilie or something.

Still, these old vehicles ARE still on the road. My dh drives one of them. My best friend drives another.

ARGH, sorry, I suck! I've had a LONG week at work (and an extra long day!), and can't pick up on nuances after this long week!

Pixels · Feb 6, 2009

DH drives a 99, so it's not THAT old. Lap-only belt in the center, and too old for LATCH.

He bought it when it was 1 year old. He'll drive it until it's no longer reliable. Many people do that, they buy a car and then enjoy many payment-free years until the car no longer runs before the get a new car.

Heck, mine is an 02, so it's JUST new enough for LATCH. It does have lap-shoulder in all positions (that was a selling point for me). I only have about 35K miles on it, the body is in great shape, it runs great. There is absolutely no reason for me to think about replacing it at this time.

TechnoGranola · Feb 6, 2009

pixels99 said:
DH drives a 99, so it's not THAT old. Lap-only belt in the center, and too old for LATCH.

Sure, but my point was that the outboard seat belts could be used to install a child restraint, reducing head excursion by using shoulder belt and not have to worry about LATCH at all! My '91 vehicle had top tethers so I had to use the seat belt AND the top tether. Seems silly, when they could have designed it to use the shoulder belt and not bother with the top tether (outboard only). The centre position is often a small seat, a lumpy seat, a weird angled seat, anyway, so why not focus on the seat WITH belts that can install a seat rather than focusing on seats with belts that need additional anchorage?

NannyMom · Feb 6, 2009

TechnoGranola said:
Sure, but my point was that the outboard seat belts could be used to install a child restraint, reducing head excursion by using shoulder belt and not have to worry about LATCH at all! My '91 vehicle had top tethers so I had to use the seat belt AND the top tether. Seems silly, when they could have designed it to use the shoulder belt and not bother with the top tether (outboard only). The centre position is often a small seat, a lumpy seat, a weird angled seat, anyway, so why not focus on the seat WITH belts that can install a seat rather than focusing on seats with belts that need additional anchorage?

Many, many vehicles have center seats that are not lumpy, small, etc. There needs to be a way of installing all carseats in all seating positions. Until we get rid of all lap belts, or put LATCH in all positions in all cars, this is just what we have to deal with

I'd much rather my daughter (an only child) ride in the center seat with extra harndware (top tether) than outboard with no extra hardware (even if the seat was designed to work as you describe). It's furthest from all points of impact. When possible, that's where she'll sit

TechnoGranola · Feb 6, 2009

NannyMom said:
It's furthest from all points of impact. When possible, that's where she'll sit

No it's not. It's not furthest from either side impact point. The furthest point is the side opposite the impact. A child on the opposite side of the impact will fare better than a child in the centre (I do have links showing that somewhere!). The middle is merely a compromise since you can't know what side you will be hit on. It does not mean a child is always best off in the centre.

Head excursion for little FFers

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