This study investigates the effects of different design factors on submarining using sled tests and mathematical simulations. The study is focused on the following three factors: (1) the position of the pillar loop (the D-ring); (2) the leg (foot) position; and (3) belt slack. The results of the study show that: (i) occupants are more likely to submarine, if the upper belt anchorage is far behind their shoulder (as in a rear seat or in a front seat in a two-door car); (ii) the closer to the seat the occupant's feet are placed, the more likely submarining is to occur; (iii) belt slack increases the risk of submarining; and (iv) a pretensioner that operates on the buckle, significantly reduces the risk of submarining. It is also shown that the angle between the lap-belt and the pelvis, measured when the belt force has peaked and dropped to 3kN, can predict the risk of submarining well.
Abstract