Modeling Two-Lane Highway Passing-Related Crashes Using Mixed Ordinal Probit Regression

One of the crucial areas in road safety is that of passing-related crashes on two-lane highways. Studies have shown that passing-related crashes that occurred due to inadequate passing sight distances were uncommon, indicating that the Manual on Uniform Traffic Control Devices constitutes safe designs. However, a proportion of such crashes were severe. Past research was conducted to assess passing sight distances and passing maneuvers. Yet, modeling passing-related crashes by type while considering unobserved heterogeneities, particularly of data that could not be collected such as driver aggressiveness, was not implemented. In this research, the severities of single- and multiple-vehicle passing-related crashes on two-lane highways were modeled using the mixed ordinal probit structure. As per the results of this research, insights were attained regarding the impacts of loss-of-control single-vehicle crashes, rollover single-vehicle crashes, single-motorcycle crashes, weather conditions, opposite-direction multiple-vehicle crashes, multiple-vehicle crashes involving motorcycles, high traffic volumes, and seatbelt use on the risk of sustaining severe injuries. Finally, passing-related crash countermeasures were suggested.