An experimental investigation was conducted to determine the effects of certain seating and restraint parameters on the tendency for an adult rear seat passenger to submarine (i.e., for the lap belt to ride over the pelvic iliac crests and penetrate the abdomen) in a 30 mph delta-v frontal collision. Four parameters were investigated: type of restraint (lap belt only or three-point belt), seat cushion stiffness, seat cushion height, and lap belt angle (within the range from 20 to 75 degrees, as specified in FMVSS 210, "Seat Belt Assembly Anchorages"). Lap belt angle was found to be a highly significant parameter ― the shallower the angle, the greater the submarining tendency. The tendency to submarine also appeared to be greater for three-point belted occupants than for lap-only belted occupants, although lap belt forces were much less for three-point belts. Results indicated that only one injury (AIS 1) would have occurred out of six cases of submarining in three-point belts.