Well, my personal opinion would be that all RF seats should be in contact with dash/seat or in a very close proximity at least- 1/3 of an inch for example. Physics is the same in Europe and in the US and as you saw from this article true run down time comes only with a rigid seat that does not move. That is exactly why rigid Isofix is safer in FF and when it comes to RF that difference dissapears because of the braced seats. But I am not an engineer- I am just expressing my opinion and my beliefs.
I would actually directly argue with you about that 1/3 of an inch in front of a dash. While a small amount of space, it is still enough space for a seat to rotate a little, resulting in the child impacting the shell when the shell of the seat impacts the hard dashboard.
As I understand it, advanced airbag systems are becoming more common place in Europe as well, and switches are becoming less common.
Yes, I know your Latch is simply Isofix anchors attached to a belt which stretches. Maybe it is part a US logic or something, but European Isofix does not stretch. And as LISmama810 mentioned a bungee rope- yes it is a good example but you are imagining it from the wrong perspective. You see the rope as the system holding the seat in place, but this rope actually is the internal harness that must stretch in order to slow down gradually the body of the child.
But at what point is the internal harness stretching? In a North American seat, the shell is rotating downwards and the carseat is doing the bulk of the hard work during that time. The harness of a rf'ing seat isn't going to have loading on it until the seat starts to rebound - which is involving much less force by the time it happens.
A number of years ago, some child restraint manufacturers didn't reinforce all harness slots for use with a ff'ing child. In fact, they often only reinforced the very top slots to accomodate the forces that a ff'ing child placed on the harness system. Harnesses ripped through the shells of seats in collisions when parents failed to move the straps to the reinforced slots - yet those same seats didn't fail rf'ing because the force just isn't there.
You are correct that the vehicle body is the primary point of protection for the occupants of the vehicle. I know many people on this site, myself included, have shopped for vehicles and had very specific crash test requirements and minimum safety features that we've been willing to consider when purchasing a vehicle. We understand the important role that the vehicle plays in a collision. But the carseat serves multiple purposes - it spreads the force over more parts of the body, it keeps the child in the protected passenger space, and it allows the child a more gradual stop while the vehicle itself is absorbing energy.
Britax has purposefully put features in to it's seats in North America which actually allow the child to have increased movement in higher speed collisions. Likewise, Diono has a device called the safestop that is for ff'ing children under 40lbs when the seat is top tethered. Manufacturers recognize that too abrupt a stop doesn't benefit the child and that a more gradual stop means that they don't have as much force applied to their body. This doesn't mean that excessive movement is a good thing. Seats have standards that they have to meet in terms of how much forward movement they are allowed to have, or in the case of rf'ing seats, how much downward rotation they are allowed to have.
Swedish seats are ultimately designed a lot differently from North American seats. However, I can tell you that if I was installing a rf'ing seat in a front seat with a disabled airbag - as you would in a pick-up truck without a back seat, I would rather have it fully against the front dash so that the downward movement was prevented in the first place because preventing the movement would be more preferable than the seat impacting the dash early on in the collision sequence.
Just my thoughts.
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