A New Approach to Evaluating Roundabout Safety Using Conflicting Volumes and Delay

Author(s): Taha Saleem, Robert Henderson, Bhagwant Persaud
Student Paper Competition: 2nd Place

Slidedeck Presentation:

7C - Saleem


One of the primary goals of transportation agencies around the world is to reduce crashes and potential crashes attributable to transportation facilities as well as minimize the potential for human error and provide a forgiving intersection environment. Roundabouts are constructed mostly because of their safety and capacity benefits; they provide a solution that can potentially reduce crashes at intersections. According to Transportation Association of Canada’s “Synthesis of North American Roundabout Practice”, roundabouts are shown to reduce injury collisions by approximately 75% as compared to stop control or traffic signals. The main objective of this study is to investigate the viability of roundabout crash prediction models based on estimated total peak hour conflicting volumes and the overall roundabout delay and to compare these models to conventional models based on actual flows. Samples of multi- and single-lane roundabouts from the Region of Waterloo, City of Ottawa, and Washington State were used. State-of-the-art, generalized linear modeling (GLM), with the specification of a negative binomial (NB) error structure, was used to develop the crash prediction models. Models were developed linking crashes to the estimated total peak hour conflicting volume and the overall roundabout delay. The results are promising in that the new models yield results that closely match those from the conventional models.