Operational and Safety Performance Evaluation of Parallel Flow Intersection

Unconventional arterial intersection designs have recently gained popularity as an alternative solution to alleviate congestion and mitigate safety problems of at-grade signalized intersections. This study investigates the operational and safety performance of the parallel flow intersection (PFI) under different balanced and unbalanced traffic volume conditions in comparison with a conventional counterpart using VISSIM microsimulation and Surrogate Safety Assessment Model software. The operational performance of the two intersections was based on the overall intersection capacity and the average vehicle delay. The safety performance, on the other hand, was based on the number and severity of simulated conflicts. The results showed that the PFI had a higher capacity compared with the conventional intersection under balanced volume conditions. Under unbalanced volume levels, the PFI outperformed the conventional intersection especially with an increase of left-turn volumes. Moreover, the PFI enhanced the safety conditions relative to the conventional intersection by eliminating all the crossing conflicts under all balanced and unbalanced volume levels and reducing the total number and severity of conflicts at all volume conditions. The study provides guidelines for the optimal spacing distance between the main and secondary intersections for the implementation of the PFI based on its safety and operational impacts on the intersection.