The risk of death increased the more obese the driver was, according to the study released online Monday in the BMJ Group’s Emergency Medicine Journal. …

The study’s authors pointed to previous research that showed that an obese driver’s lower body is propelled farther upon impact before a seat belt engages the pelvis. The driver’s additional tissue prevents the belt from fitting snugly, but the upper body is held back.

The authors suggest that while obese people may have underlying health problems, vehicle design may need to change to provide better protection.