Question about seat position and tether strap

I have a Mazda CX7 that I have both an infant seat and a Britax Marathon in. The Marathon is currently in the center position forward facing and the infant seat is on the side rear facing. My problem is I can't use the tether strap on the Marathon without losing the ability to put my stroller in the back of my car. Is it safer to move the Marathon to the side and tether it or keep it in the middle untethered?

Thank you.

What is the child's age, size, and weight?

:yeahthat:

Middle, untethered, if the child is too big to rear face.

Pixels said:

Middle, untethered, if the child is too big to rear face.

Click to expand...

Hmm, I would disagree with that.

I would too, especially if the child is too heavy to rear-face.

http://www.nhtsa.dot.gov/cars/rules/rulings/UCRA-OMB-J08/Econ/RegEval.213.225.html

In the event of a crash, the tether will prevent head excursion and reduce the chance of serious head injury. An estimated 6 to 17 additional lives will be saved by tether anchorages.

Click to expand...

Not the best reference since it is prospective rather than retrospective, but I'm not aware of anything retrospective in this area.

Pixels said:

http://www.nhtsa.dot.gov/cars/rules/rulings/UCRA-OMB-J08/Econ/RegEval.213.225.htmlNot the best reference since it is prospective rather than retrospective, but I'm not aware of anything retrospective in this area.

Click to expand...

?? Is there data showing that more lives will be saved by being in the middle than top tethered? I'm not sure how this relates to what you said earlier

Not directly, but we know that center is approximately 35% safer than outboard. I'm saying that fewer lives are saved by being top tethered compared to the number of lives saved by being center vs outboard.

I would move the MA outboard and tether it. I'm in Canada though and for the situation you describe, that's the only legal option (all FFg seats must be TTd).

Generally, the rule is the least protected child goes in the most protected position. In theory, that would mean the FFg child goes center and the RFg child outboard. BUT, IMO, a FFg install isn't safest if it isn't TTd. So, I would not recommend a FFg install without use of the TT.

JMHO.

Pixels said:

Not directly, but we know that center is approximately 35% safer than outboard. I'm saying that fewer lives are saved by being top tethered compared to the number of lives saved by being center vs outboard.

Click to expand...

I haven't heard 35% - can you post a link?

The tether is going to help prevent injury in all types of crashes. Being in the center will only provide additional protection in a side-impact, and even then only in a side-impact on the same side where the child would have been sitting otherwise.

Pixels said:

http://www.nhtsa.dot.gov/cars/rules/rulings/UCRA-OMB-J08/Econ/RegEval.213.225.htmlNot the best reference since it is prospective rather than retrospective, but I'm not aware of anything retrospective in this area.

Click to expand...

Pixels said:

Not directly, but we know that center is approximately 35% safer than outboard. I'm saying that fewer lives are saved by being top tethered compared to the number of lives saved by being center vs outboard.

Click to expand...

There's some math confusion here. You're comparing two different things, and we don't even have a base for either of the figures, so I don't think you can draw any hard and fast conclusions based on these two seats of numbers.

Defrost said:

I haven't heard 35% - can you post a link?

The tether is going to help prevent injury in all types of crashes. Being in the center will only provide additional protection in a side-impact, and even then only in a side-impact on the same side where the child would have been sitting otherwise.

Click to expand...

Child occupants seated in the center had an injury risk 43% less than children seated in either of the rear outboard positions.

Click to expand...

Evans and Frick2 found an overall 16% decrease in fatality risk for all age occupants when seated in the center as compared with the outboard seat. For restrained children, Braver et al3 found that those seated in the center rear experienced a reduction of 24% in fatality risk when compared with those in the rear outboard seating positions.

Click to expand...

http://pediatrics.aappublications.org/cgi/content/full/121/5/e1342

Top tethering does not help prevent injury in all types of crashes. It will only make a difference if all the variables (crash severity, type of crash, install tightness, height/weight of child, harness tightness, etc) result in head excursion that causes impact to the vehicle interior hard enough to cause injury when untethered, and those exact same variables with a tether result in no injury.

As for using the two studies to draw comparisons of relative safety, the studies are comparing different things. One study looked at fatality rates, the other looked at injury. I'm going to go out on a limb and say that for the purposes of this comparison, relative injury rate is related to and indicative of relative fatality rate. One gave results in concrete numbers, the other gave it in percentages, so we need to convert numbers to percentages. In 1999 (the year closest to the NHTSA tethering study for which I have data), 564 children age 1-4 were killed in motor vehicle crashes. Six lives saved out of 564 would be <1.1%; 17 lives saved out of 564 would be 3.0%. Therefore top tethering is approximately 1-3% safer than not tethering. Compared to 16%, 24%, or 43% safer (depending on age group and study) in the center versus outboard, I think it's clear that being in the center outweighs top tethering.

For restrained children, Braver et al3 found that those seated in the center rear experienced a reduction of 24% in fatality risk when compared with those in the rear outboard seating positions.

Click to expand...

My understanding was that this was based on the fatality risk of the child on the side that was struck, and that being outboard on the opposite side of a side-impact was actually less risky than being in the center.

Meaning, being in the center is only safer because you don't get to pick which side you get hit on. That's great if you've got only one kid, of course, but when you've got two it becomes quite a bit more academic. The one you're putting outboard is already at greater risk - why not not really minimize the other child's risk by placing him/her even further from the point of impact 50% of the time?

I'm not sure I explained that well - does it make sense?

To address the original question, if the problem is the tether anchor is back by the rear hatch, you could always detach the tether to put the stroller in, then rehook the tether.

Defrost said:

My understanding was that this was based on the fatality risk of the child on the side that was struck, and that being outboard on the opposite side of a side-impact was actually less risky than being in the center.

Click to expand...

The particular study that you quoted specifically says that it is overall reduction in fatality rate for center vs outboard from all impact directions and is not limited to outboard on the side that was struck.

I have seen the study (somewhere...) that says that if you can pick which side you get hit on, then you want to be outboard on the opposite side, not center. That is correct, it's just not what the studies I was quoting were saying.

Meaning, being in the center is only safer because you don't get to pick which side you get hit on. That's great if you've got only one kid, of course, but when you've got two it becomes quite a bit more academic. The one you're putting outboard is already at greater risk - why not not really minimize the other child's risk by placing him/her even further from the point of impact 50% of the time?

I'm not sure I explained that well - does it make sense?

Click to expand...

I does make sense at first blush, however, the difference between center and outboard with impact on the same side does not equal the difference between center and outboard with impact on the opposite side. I'm going to make up some numbers based on my memory of the gist of it for discussion. Let's say that being outboard on the same side as impact is 50% more likely to be fatal than being center. And center is 10% more likely to be fatal than outboard on the opposite side from impact. This is because on the same side as impact, it only takes a few inches of intrusion before you get in that child's space, but it takes closer to 2 feet of intrusion before you get into the center child's space. More crashes will have some intrusion than a lot of intrusion. That is why there is a bigger safety benefit by not being on the same side as impact, vs moving from center to opposite side.

So you have a two-row vehicle and two children. At least one child has to go outboard, and the other child can either be outboard or center. Scenario A, one child is outboard driver's, one is center, and side impact is on the driver's side. The child who is in the center could have been 10% safer by being outboard. Scenario B, one child is outboard driver's, one is center, and side impact is on the passenger's side. The child who is in the center was 50% safer by being in the center. The child is overall safer by being in the center than s/he would be by being outboard.