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Use of the top tether attachment in three commonly available anchor points provides added restraint of child restraint systems (CRS). Three tether attachment positions were used; floor, behind the head rest (parcel deck) and at the ceiling. The three anchor points are comparable in efficacy while no tether allows increased travel of the anthropomorphic test device (ATD) head. Two series of six tests were conducted at a max speed of 20 mph and peak deceleration of 16 G's using a deceleration sled test apparatus. The first series of tests was conducted at a 90 degree impact angle. On average there is 9% less head travel when using the tether attachment compared to not using the tether attachment, all other conditions begin equal. The second series of tests was conducted at a 73 degree impact angle, there is 15% less head travel when using the tether attachment compared to not using the tether attachment, all other conditions begin equal. Using a top tether in side impacts is more effective at restraining a child seat than not using a top tether, all things being equal. When no top tether is used with properly installed lower anchors compared to no tether and improperly installed lower anchors, there is a 21% increase at 90 degrees and a 19% increase at 73 degrees in head travel.
Neal et al. (Mon,) studied this question.