Development of conflict-based safety performance function for safety evaluation of urban roundabouts in India

This study evaluates the safety performance of urban roundabouts in India using conflict-based safety performance functions (SPFs). High-resolution aerial videos were utilized to extract vehicle trajectories, and the surrogate safety assessment model was employed for conflict identification. Data were collected from 27 roundabouts across various Indian cities, focusing on non-lane-based heterogeneous traffic conditions. Four SPFs were developed utilizing a generalized linear model with negative binomial distribution and log link function for different proximity levels based on time-to-collision and post-encroachment time values. Key factors influencing conflict frequency included conflicting traffic volume, occupancy time, ratio of approaching and conflicting traffic volume, percentage of cars and motorcycles, inscribed circle diameter, roundabout symmetry, and number of legs. The developed conflict frequency prediction models fitted well and demonstrated robust predictive performance. This proactive framework for roundabout safety assessment can be followed to enhance road safety in developing nations.