Priority violation influence on roundabout safety in mixed traffic conditions

Roundabouts are increasingly being implemented worldwide as safer options in comparison to the traditional intersections. However, in Indian mixed traffic conditions priority violations occur frequently at roundabouts causing disruption to the flow.  This study deals with the effect of priority violations (priority limitation and priority reversal) on the safety of roundabouts by using time to collision (TTC) as a primary surrogate safety measure (SSM) to quantify the frequency and severity of conflicts resulting from priority violations, considering conflicts with TTC values less than 2 seconds. Twenty-two approaches from six roundabouts with diverse geometric and traffic characteristics were analyzed, with vehicle trajectories and conflict data extracted from video footage using DataFromSky software. A generalized linear model (GLM) with a negative binomial (NB) distribution and logarithmic link function was used to model frequency of critical conflicts. The results reveal that wider entry widths, larger entry angles, and higher circulating volume significantly increase the frequency of priority violations and critical conflicts. The study also found that priority reversal, while reducing immediate conflict frequency, disrupts the operational efficiency of roundabouts. The findings provide actionable insights for practitioners and policymakers aiming to improve roundabout safety and operational performance in complex, heterogeneous traffic environments.