Effects of High Levels of Obesity on Lap and Shoulder Belt Paths

Obese occupants have higher risks of fatalities and injuries in frontal crashes than normal‐weight individuals. In particular the chest and the lower extremities are the body regions that are more likely to be injured for obese than non‐obese occupants. Previous studies demonstrated that obesity increases the amount of belt webbing used by drivers, and have shown that lap belt placement tends to be higher and further forward relative to the pelvis, but have not characterized the belt paths in detail with respect to skeletal landmarks. Moreover, previous studies have used data from only a few individuals with BMI>35 kg/m2. Driving postures and belt fit of 52 men and women with BMI from 31 to 59 kg/m2 (median 38 kg/m2) were measured in laboratory mockup. The paths of the lap and shoulder portions of the belt were captured using a three‐dimensional coordinate digitizer. The paths were fit using basis splines and a statistical analysis was conducted to examine the effects of overall body dimensions on belt paths. For both men and women, the torso portion of the belt routed further forward of the bony landmarks at the sternum and more laterally on the inboard (buckle) side, passing higher on the ribcage, but the effect was larger for women. The torso belt path was further forward, relative to the top of the sternum, for women than for men, reflecting greater thickness of breast tissue. For men, higher BMI was associated with a lower but more forward belt position relative to the pelvis. The effects of these differences in belt path with increased adiposity should be studied further using human body models.