But there's only one single 2 inch belt across the child's chest with a belt positioning booster, while there are *two* 1.5 inch belts across his chest on the 5 point harness seat.<font face="Verdana, Arial" size="2">That and the vehicle belt is 2 inches wide versus most CRS harnesses at 1.5 inches in width. The 1.5 typically stretches more. </font>
The way I read this, it seems the engineer is saying that the 5 point is a good thing for this particular measure; it reduces HICS and chest G's. I don't think he's saying the smaller belts are really worse. It's just that using the 5-point to hold the kid, and then the seat belt to hold the seat/kid combo to the car, there will be more overall motion since there are more points of compliance in the system (i.e.- the vehicle belt stretches, the 5 pt stretches, the seat deforms). That AND the 1.5" belts would typically be more compliant than the 2" vehicle belt, period. More points of compliance = more energy dissipative motion = better HICS and chest Gs.<font face="Verdana, Arial" size="2">
HICS [federal Head Injury Criteria] and chest G's are generally lower in a 5-point than in a lap/shoulder belt. There's more ride down to absorb the crash forces since both the 5-point and vehicle belt stretch and the CRS shell flexes. That and the vehicle belt is 2 inches wide versus most CRS harnesses at 1.5 inches in width. The 1.5 typically stretches more.
As I've said before, I will have no problem using a BPB for my son, unless he isn't mature enough to stay sitting correctly OR unless there is a reasonable alternative which is readily available.<font face="Verdana, Arial" size="2">Originally posted by 3odys4me:
It's *not* so clear after all.