Seat belts have been shown to be effective in reducing the number of serious injuries in car crashes. However, some injuries have been reported in accident data due to improperly fitted seat belts. This occurs, for example, when the belt rides above the anterior superior iliac spines (ASIS) of the pelvis before impact and loads the abdomen. This loading scenario is often referred to as “submarining”.

The objective of this study was to identify the abdominal injury response when a lap belt is initially placed above the ASIS and dynamically cinched, and to determine injury thresholds. For this purpose, 14 post mortem human subjects (PMHS) were tested.

The set-up consisted of a rigid seat with an adjustable seat back and a dynamic cinching device linked to the webbing of a lap belt. The load applied on the lap belt peaked between 2.9 and 7.1 kN while it stabilized from 2 to 4.4 kN at a cinching speed of 6 m/s. Injuries were found in 3 of the 14 tests, at peak loads varying between 6.0 to 6.8 kN with a stable load of 3.6 to 4.1 kN. In these tests, the amount of lap belt web pull in was between 190 to 194 mm.

Data revealed that abdominal responses seem to vary not only with belt pull-in distance and force but also with anthropometric data. Though the results are not significant, the ratio between subject weight and size seem to affect the results.

The findings of this study were used to aid for the design of seat belt tensioning systems. An optimization of the restraint performance needs to be evaluated.