Vehicle Model Year and Crash Outcomes: A CIREN Study

Abstract

Objective: To quantify the effect of model year (MY) on the occurrence of severe injuries and death after involvement in motor vehicle crashes. Methods: Cases involving adult front seat occupants of vehicles MY ≥ 1994 equipped with frontal airbags were selected from the Crash Injury Research and Engineering Network (CIREN) database. Cases were grouped by MY: 1994–1997, 1998–2004, and 2005–2007 (MY groups [MYG] 1, 2, and 3, respectively. MYGs were compared in relation to mortality, Injury Severity Score (ISS), and the occurrence of Abbreviated Injury Severity score (AIS) 3+ and AIS4+ injuries to each body region using Mantel Haenszel chi-square, Kruskal-Wallis, and Bonferroni corrected t test. To adjust for confounders, multiple logistic regression models were built to explore the association of MYG with death. Covariates included age, BMI, delta v, principal direction of force (PDOF), restraint use, and vehicle type. Results: A total of 1888 cases was distributed within MYG1 (34%), MYG2 (62%), and MYG (34%). Age, gender, BMI, and PDOF distribution did not differ among MYGs. Though ISS distribution was not different, a decrease in the occurrence of AIS4+ of the thorax and spine regions was noted over time. Mortality also decreased over time (18, 9, and 4% MYG 1, 2, and 3, respectively). Multivariate analysis revealed a protective effect of MYG2 and MGY3 (odds ratio [OR], 0.57 [0.44–0.75] and 0.22 [0.07–0.50], respectively) in relation to death. Conclusions: Front seat occupants of later MY vehicles injured during crashes experience a decreased likelihood of very severe thoracic injuries, spinal injuries, and death.