PURPOSE: This is a study of the influence of an unbelted rear occupant on the risk for severe injury to the front-seat occupant ahead of them in frontal crashes. It provides an update to earlier studies.
METHODS: 1997-2015 NASS-CDS data was used to investigate the risk for severe injury (MAIS 4+F) to belted drivers and front passengers in frontal crashes by the presence of a belted or unbelted passenger seated directly behind them or without a rear passenger. Frontal crashes were identified with GAD1 = 'F' without rollover (rollover ≤ 0). Front- and rear-outboard occupants were included without ejection (ejection = 0). Injury severity was defined by MAIS and fatality (F) by TREATMNT = 1 or INJSEV = 4. Weighted data was determined. The risk for MAIS 4+F was determined using the number of occupants with known injury status MAIS 0+F. Standard errors were determined.
RESULTS: The risk for severe injury was 0.803% ± 0.263% for the driver with an unbelted left rear occupant and 0.100% ± 0.039% with a belted left rear occupant. The driver's risk was thus 8.01-times greater with an unbelted rear occupant than with a belted occupant (p < 0.001). With an unbelted right-rear occupant behind the front passenger, the risk for severe injury was 0.277% ± 0.091% for the front passenger. The corresponding risk was 0.165% ± 0.075% when the right-rear occupant was belted. The front passenger's risk was 1.68-times greater with an unbelted rear occupant behind them than a belted occupant (p < 0.001). The driver's risk for MAIS 4+F was highest when their seat was deformed forward. The risk was 9.94-times greater with an unbelted rear occupant than with a belted rear occupant when the driver's seat deformed forward. It was 13.4% ± 12.2% with an unbelted occupant behind them and 1.35% ± 0.95% with a belted occupant behind them.
CONCLUSIONS: Consistent with prior literature, seatbelt use by a rear occupant significantly lowered the risk for severe injury to belted occupants seated in front of them. The reduction was greater for drivers than for front passengers. It was 87.5% for the driver and 40.6% for the front passenger. These results emphasize the need to belt reminders in all seating positions.
Language: en
Keywords
Front impacts; belt effectiveness; belted versus unbelted rear occupants; front seats; rear occupant loading