When to Decide to Convert a Roundabout to a Signalized Intersection: Simulation Approach for Case Studies in Jeddah and Al-Madinah

The increasing congestion on transportation networks has raised inconvenience among the network’s users, especially in major cities intersections where there are frequently problems experienced like delays and low levels of service. Roundabouts are always offered as a solution or an alternative from existing signalized intersections believing in their substantial delays reduction. However, it is essential to adopt advanced transportation analysis tools to ensure whether this solution performance would last overtime or not. This study focuses on evaluating the performance of two real existing roundabouts in Jeddah and Al-Madinah cities over time. It aims at analyzing and assessing the level of service of these two intersections in the case of existing roundabouts and their parallel solution of signalized intersections to decide when it is better to convert the existing roundabout into a signalized intersection. Sidra and Synchro, as the simulation tools are fed with synthetically generated demand scenarios, represent the normal increase in traffic with passing years. As a result, the underperforming year is easily detected for both intersections. Also, the impact of the rise in left-turn volume is evaluated for both solution types. It is expected that the proposed framework would help practitioners to continuously assess the applicability of converting roundabout solutions to signalized intersections besides determining the span of service.