Contributing Factors to Run-Off-Road Crashes Involving Large Trucks under Lighted and Dark Conditions

Previous studies have examined the relationships between run-off-road (ROR) crashes and the contributing factors; however, the impact of lighting conditions has been insufficiently addressed. As a result, the objective of this study was to research the effect of lighting conditions on the injury severity of ROR crashes that involve large trucks. Based on the crash data pertaining to large trucks in the state of Oregon from 2007 to 2013, two separate mixed logit models were developed to capture the contributing factors that affect injury severity in each lighting condition. The levels of injury severity sustained by truck drivers were categorized into three main categories: severe injury (fatal and incapacitating), minor injury (nonincapacitating and possible injury), and no injury. The mixed logit model was used to account for unobserved factors (i.e.,unobserved heterogeneity). Estimation results indicated that there are significant differences between dark and lighted conditions, that the level of injury severity outcomes was highly influenced by several complex interactions between factors, and that the effects of some factors could vary across observations. The contributing factors include driver, traffic flow, roadway geometric features, land use, and time characteristics. (C) 2017 American Society of Civil Engineers.