Effect of Tether Routing and Anchor Location on Child Restraint Kinematics

Abstract

A series of 16 sled tests were performed to examine the effect of tether routing with respect to the vehicle head restraint on the kinematics of the Hybrid III 3-year-old ATD secured in two forward-facing harnessed child restraints. The main outcome of interest was whether a particular tether routing provided a safety benefit by reducing head excursions. Two different child restraints were used, one with a single strap tether and the other with a V-style tether. The single strap was routed either under or over the head restraint, while the V-style tether was routed either under or around the head restraint. Three different tether anchor locations were evaluated, representing locations on the roof, rear filler panel, or the lower vehicle seat-back. Two different vehicle seats were mounted to the FMVSS 213 sled buck. One was the outboard second-row seat from the 2011 Ford Explorer, while the other was the center second-row seat from the 2011 Jeep Grand Cherokee. Child restraints were installed with lower anchors in the Explorer seat and the seatbelt in the Grand Cherokee. The specific tether routing did not have an effect on head excursion. Rather, head excursion increased as the length of tether webbing between the tether attachment point on the child restraint and the tether anchor hardware increased. The results of these tests suggest that the tether routing providing the shortest distance to the vehicle tether anchor be recommended, as long as that routing allows the user to achieve a tight tether installation. This study is limited by the use of only two different vehicles and two different child restraints for testing.