The objective of this study was to investigate occupant injury patterns and
predictors in rear-impact crashes using recent US field data. Cases were queried
from the Crash Investigation Sampling System (CISS, 2017–2023) and the Crash
Injury Research and Engineering Network (CIREN, 2017–2024), yielding 1923
front-row outboard occupants from 1533 crashes. Crash documentation and vehicle
photographs were manually reviewed to classify seatback deformation magnitude
and secondary impact severity. Multivariable logistic regression models
estimated associations between occupant, vehicle, and crash characteristics and
Abbreviated Injury Scale (AIS) ≥ 2 and AIS ≥ 3 injury outcomes across body
regions. Sensitivity analyses included CISS-only, weighted, single-event, and
interaction models. Thoracic injuries were further subdivided into skeletal and
cardiopulmonary categories. Findings reflect associations within the pooled CISS
+ CIREN analytic sample rather than nationally representative injury rates.
Seatback deformation and multievent crash classification are proxy measures and
may introduce misclassification and residual confounding.
A total of 188 occupants sustained AIS ≥ 2 injuries and 81 sustained AIS ≥ 3
injuries. Head injury was the most frequent AIS ≥ 2 outcome, while thoracic
injury was the most frequent serious injury outcome, accounting for 60% of AIS ≥
3 cases. Across AIS ≥ 2 and AIS ≥ 3 models, crash severity (delta-v) was the
most consistent predictor of injury. Age was strongly associated with injury
across most AIS ≥ 2 outcomes and several AIS ≥ 3 models, particularly for
overall maximum Abbreviated Injury Scale (MAIS) and thoracic injury. Seatback
deformation was associated with injury across multiple models after controlling
for crash severity and occupant characteristics, with severe deformation showing
stronger associations with AIS ≥ 3 outcomes. Unbelted status was associated with
abdominal, pelvic, and lumbar spine injury. Female sex was associated with
thoracic injury, primarily attributable to cardiopulmonary rather than skeletal
injury. These findings highlight statistical associations between seatback
deformation severity, restraint status, occupant characteristics, and injury
outcomes in rear-impact crashes.
