Examining the Effects of Geometric Features, Traffic Control, and Traffic Volume on Crash Frequency at Urban Intersections

Intersections are sites where traffic crashes are highly concentrated. This is because conflicting traffic maneuvers are highest at the intersections and, therefore, they are more prone to crash occurrence. An accurate understanding of the relationships between various geometric features, traffic flow and crashes in the influence area of intersections, could help reduce these crashes by suggesting appropriate countermeasures. Safety performance functions are the tools to understand these relationships. In this study, we developed safety performance functions specific to Antwerp, Belgium, for urban intersections, using multiple functional forms of a Poisson-gamma framework considering total crash counts. A dataset consisting of six years (2010–2015) of intersection crashes, traffic flows (major and minor), and geometric features was created. This paper documents the development process of safety performance functions for signalized and un-signalized intersections, connecting roadway geometry and traffic characteristics to intersection related crashes and, thus, estimating the impact of predictor variables on the crash occurrence, so as to facilitate the safe design. The findings indicate several road geometric and traffic variables that have a significant impact on crashes at urban intersections. The results revealed that to improve intersection safety, enough attention must be paid to the number of through lanes of a minor approach, intersection skewness, size, and presence of crosswalks on the approach roads. Furthermore, it was found that an early inquiry into the model’s functional form could result in more accurate estimates of crash frequency.