The rural two-lane highway in the Southeastern United States is frequently associated with a disproportionate number of serious and fatal crashes and as such remains a focus of considerable safety research. The Georgia Department of Transportation spearheaded a regional fatal crash analysis to identify various safety performances on two-lane rural highways and offer guidance for identifying suitable countermeasures to mitigate fatal crashes. The fatal crash data used in this study were compiled from Alabama, Georgia, Mississippi, and South Carolina. The database, developed for an earlier study, included a total of 557 randomly selected fatal crashes from the years 1997 and/or 1998 (varied per state). Each participating state identified the candidate crashes and performed physical or video site visits to construct crash databases with enhance site-specific information.
Motivated by the hypothesis that single- and multiple-vehicle crashes arise under fundamentally different circumstances, the research team applied binary logit models to predict the probability that a fatal crash is a single-vehicle run-off-road fatal crash given roadway design characteristics, roadside environment features, and traffic conditions proximal to the crash site. A wide variety of factors appears to influence or be associated with single-vehicle fatal crashes. This paper also includes a model transferability assessment where the authors determined that lane width, horizontal curvature, and ambient lighting are the only three significant variables consistent for the single-vehicle run-off-road crashes for all study locations.