Injury Risks in Frontal Crashes by Delta V and Body Region With Focus on Head Injuries in Low-Speed Collisions

Abstract

Purpose: This study investigated injury risks in frontal crashes by belt use and crash severity (delta V) with a focus on studying whether there is a pattern to the crashes causing serious head injuries in low-speed frontal collisions. Methods: 1996–2007 National Automotive Sample System–Crashworthiness Data System (NASS-CDS) was analyzed for frontal crashes involving front-outboard occupants. Light vehicles were included with model year 1997+. Injuries of maximum severity MAIS 0–6 and fatalities were determined by crash severity and belt. Body region injury (AIS 0–6) was also determined. NASS-CDS electronic cases involving <15 mph crashes were evaluated to determine the crash circumstances causing serious head injury (AIS 3+) in occupants with overall severe injuries (MAIS 4+F). Results: More than half (51.3%) of belted occupants in 10–15 mph delta V crashes were uninjured compared with 30.2 percent for unbelted occupants. The ratio of the fraction (relative risk) of belted occupants who were uninjured to the fraction of unbelted, uninjured occupants was highest at 3.74 in the 30–35 mph delta V. For 10–15 mph crashes, 0.40 ± 0.15 percent of unbelted occupants were severely injured (MAIS 4+F) compared to 0.033 ± 0.009 percent for belted occupants. For 30–35 mph crashes, 8.51 ± 2.20 percent of unbelted and 5.83 ± 1.93 percent of belted occupants were severely injured. Overall, seat belt use was 87.4 percent effective in preventing severe injury (MAIS 4+F). The effectiveness decreased with increasing crash severity. The highest relative risk for severe injury of unbelted compared to belted occupants was 12.3 in crashes of 10–15 mph delta V. The relative risk was 8.8 in <10 mph crashes. Overall, the relative risk was 8.0 for severe injury (MAIS 4+F) in frontal crashes. 16.5 ± 0.98 percent of unbelted occupants experienced serious (AIS 3–6) injury. This risk was 6.49 times greater than the 2.53 ± 0.10 percent risk with belted occupants. The largest relative risk for serious injury (AIS 3–6) was to the neck (367 times), face (15.5 times) and head (10.2 times). Conclusions: The highest relative risk for severe injury of unbelted occupants was in frontal crashes <15 mph. Most of the crashes involved multiple impacts and air bag deployment in the accident sequence. The use of long fill-time side curtains, additional curtain deployment logic, limited deflation front air bags and broader curtain coverage of the front interior may address these injuries.