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Effect of realistic vehicle seats, cushion length, and lap belt geometry on child ATD kinematics

This series of sled tests examined the effect of using real vehicle seats on child ATD performance. Cushion length was varied from production length of 450 mm to a shorter length of 350 mm. Lap belt geometry was set to rear, mid, and forward anchorage locations that span the range of allowable lap belt angles found in real vehicles. Six tests each were performed with the standard Hybrid III 6YO and 10YO ATDs. One additional test was performed using a booster seat with the 6YO. An updated version of the UMTRI seating procedure was used to position the ATDs that positions the ATD hips further forward with longer seat cushions to reflect the effect of cushion length on posture that has been measured with child volunteers. ATD kinematics were evaluated using peak head excursion, peak knee excursion, the difference between peak head and peak knee excursion, and the minimum torso angle. Shortening the seat cushion improved kinematic outcomes, particularly for the 10YO. Lap belt geometry had a greater effect on kinematics with the longer cushion length, with mid and forward belt geometries producing better kinematics than the rearward belt geometry. The worst kinematics for both ATDs occurred with the long cushion length and rearward lap belt geometry. The improvements in kinematics from shorter cushion length or more forward belt geometry are smaller than those provided by a booster seat. The results show potential benefits in occupant protection from shortening cushion length, particularly for children the size of the 10YO ATD.

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