Effects of Intersections on the Safety of Horizontal Curves

Both horizontal curves and intersections are generally considered high-risk locations in roadway safety. Although extensive research has been conducted separately on the safety of curves and intersections, the safety performance of curves as affected by their spatial relationship with intersections has not been fully understood. Previous research has not examined this relationship because of the use of limited or pre-existing datasets that did not include intersection data in the analysis. This study addresses these gaps by analyzing the spatial relationship between curves and intersections, utilizing a large dataset of over 8,000 rural curves in Florida. The study performs a systemic analysis using this dataset and six years of statewide crash data of all injury severity levels and develops customized curve Safety Performance Functions based on various spatial relationships between curves and intersections. This study confirms that the previously identified risk factors such as traffic volume, curve radius and length, roadway speed limit, and functional classification have significant impacts on curve safety. More importantly, the study quantifies, for the first time in the literature, the influence of intersections on curves or close to curves on safety, demonstrating that curves with one or more intersections present a higher risk than curves with no intersections. The findings show that the presence of nearby intersections can increase the crash risk for curves with no intersections but can lead to a decrease in crashes for curves with one or multiple intersections. These findings can be utilized to determine high-risk curve locations for systemic safety analysis studies.