Belted driver fatalities in oblique frontal crashes

OBJECTIVE: This study analyzed fatal crashes involving lap-shoulder belted drivers in oblique frontal crashes. The front crush and occupant compartment damage of newer vehicles were compared with NHTSA and IIHS crash tests. METHODS: NHTSA online database of 2017-2023 CISS (Crash Investigation Sampling System) crashes was searched for driver fatalities in oblique frontal crashes with ±10° or ±20° PDOF and delta V of 48-160 km/h. Each case was downloaded and summarized. Only investigator confirmed belted drivers were analyzed. Since most of the crash characteristics were similar to the 0° frontal fatalities, the data was combined. A subset of newer vehicles (≤ 5 years old) was compared to frontal NCAP, small overlap and OMDB (offset moving deformable barrier) crash tests. Photographs of the vehicle deformation, front crush and intrusion were compared. RESULTS: Thirty-three (33) fatal crashes met the selection criteria, adding to 16 in pure frontal impacts. The belted drivers were 53.7 ± 19.0 years old; 59.2% were male. The majority were White (61.9%). Alcohol was found in 25% of the drivers with 15% drug use. The vehicles were 11.7 ± 6.9 years old. The fatal injuries had MAIS of 4.2 ± 1.4. The chest (73.2%) was most frequently injured with multiple rib fractures, some with heart and aorta lacerations and hemothorax. The head (32.4%) was second with serious injuries to multiple body regions. The primary source of injury was the seatbelt and steering system (73.2%). The right-front interior (24.4%) was a source in +10, +20° PDOF crashes. The driver door and A-pillar (22.0%) were sources in -10, -20° PDOF crashes. The maximum frontal crush was 105.0 ± 26.7 cm with 55.1% involving occupant compartment intrusion. In 63.8% of the crashes, the steering wheel rim was deformed indicating heavy loading by the restrained driver. The delta V was 78.6 ± 19.2 km/h (48.8 ± 11.9 mph). Most (67.3%) of the crashes were on two lane roads with the case vehicle impacting another vehicle (77.6%) or drifting off road hitting a fixed object (22.4%). The most common frontal crash types were small overlap (34.7%), full width (28.6%), offset (20.4%) and oblique offset (12.2%). CONCLUSIONS: Fatal crashes with lap-shoulder belted drivers and PDOF up to ±20° of pure frontal involve vehicle deformations and delta Vs that are higher than tests conducted by NHTSA and IIHS. The driver deaths involve significant loading of the chest with multiple rib fractures and organ lacerations. If belted drivers are to be protected, the following need to be considered: higher and lower severity sled tests to optimize occupant restraints, innovations in vehicle structures to reduce intrusion and crash avoidance technologies to reduce the speed of fatal crashes. NHTSA's 90 km/h oblique OMDB test is not severe enough to bring about meaningful changes that lower traffic fatalities. A higher severity test should be considered.