Safety Belt and Occupant Factors Influencing Thoracic & Upper Abdominal Injuries in Frontal Crashes 2011-01-1129

This paper reports on a study that examines the effect of shoulder belt load limiters and pretensioners as well as crash and occupant factors that influence upper torso harm in real-world frontal crashes. Cases from the University of Michigan International Center for Automotive Medicine (ICAM) database were analyzed. Additional information was used from other databases including the National Highway Traffic Safety Administration (NHTSA) New Car Assessment Program (NCAP), the Insurance Institute for Highway Safety (IIHS), the National Automotive Sampling System - Crashworthiness Data System (NASS-CDS), and patient data available from the University of Michigan Trauma Center. The ICAM database is comprised of information from real-world crashes in which occupants were seriously injured and required treatment at a Level 1 Trauma Center. Cases from the database were included in this study if they met the following criteria: (a) the primary collision involved a frontal type crash and; (b) case occupants were seated in front outboard positions, restrained by 3-point safety belts and deployed frontal airbags.

One hundred thirty-three (133) case occupants who sustained nearly 1,800 injuries were selected for study from the ICAM database. The study included evaluations of skeletal, organ, and vessel injuries to the upper torso. Potential influencing factors were divided into three general categories: vehicle factors (i.e., seatbelt design); occupant factors; and crash related factors.

Considering the challenges and limitations for analysis of field accident data and within the scope of this study, data indicated that: case occupants without shoulder belt load limiters experienced a higher level of upper torso harm in lower severity frontal crashes. The average Delta V for case occupants with shoulder belt load limiters was significantly higher (7.1 km/h, 34% greater crash energy) than that for the case occupants without load limiters. Case occupants with shoulder belt load limiters had significantly fewer clavicle fractures in frontal crashes. For the 62 case occupants with load limiters, the presence or absence of pretensioners did not appear to substantially change the crash severity associated with AIS ≥2 upper torso harm. Lower bone mineral density of the L4 vertebra was indicative of susceptibility to upper torso skeletal injuries. Smaller psoas muscle cross section area was indicative of susceptibility to upper torso internal and skeletal injuries.