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Differences in Injury Severities Between 2-Vehicle and 3-Vehicle Crashes

Objective and Methods: In traditional injury severity–related studies, 2-vehicle and 3-vehicle crashes are typically considered in a combinatory manner and thus the injury casual factors for these 2 crash types are implicitly assumed to be the same. This article attempts to investigate the potential discrepancy between 2- and 3-vehicle crash severities with the aid of a continuation ratio logit model with the property of partial proportional odds. Results: The modeling results show that there are a number of significant differences between 2- and 3-vehicle crash injury severities in terms of the contributing factors, the magnitude of impact, and even the direction of effects. Conclusions: The research illustrates that a series of environmental and crash factors (e.g., rear-end straight crashes, urban roadways, alcohol usage, and different driving cohorts) are statistically significant in interpreting the disparity of coefficients between 2- and 3-vehicle crash injury severity models. It raises awareness that the combined analysis of 2- and 3-vehicle crashes should be exercised with caution, particularly when safety research targets crashes with less severe injuries.