Evaluation of Traffic Performance of Ahmed Urabi Square in Baghdad City

–Azawee, Esraa Thamir Al · 2018 · DOAJ

DOI: 10.31026/j.eng.2018.06.07

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Summary

This study evaluates the traffic performance of the Ahmed Urabi roundabout in Baghdad, Iraq, a major unsignalized intersection serving over 12 million vehicles annually. The research was motivated by severe congestion, disorderly turning maneuvers, and significant economic losses due to excessive delays, estimated at 150 million Iraqi Dinars per month. The primary objectives were to assess the existing level of service (LOS) and to propose a geometric design improvement that ensures acceptable performance for both current conditions and a 20-year design horizon extending to 2037. The methodology involved a comprehensive traffic survey conducted over three weekdays to determine peak hour volumes for all intersection movements. Operational analysis was performed using Highway Capacity Software (HCS) 2000 and manual calculations based on the Highway Capacity Manual (HCM) 2000. The study analyzed the existing four-leg roundabout geometry and simulated future traffic volumes using an annual growth rate of 3%. The proposed solution involved constructing a six-lane underpass to handle through traffic in the major Alkarrada-Aljadiriya direction, thereby removing approximately 51% of the traffic volume from the intersection. The remaining intersection would be converted into a signalized roundabout with a 16-meter circulatory roadway width, four lanes per approach, and a three-phase signal timing plan. The analysis of existing conditions revealed that the Ahmed Urabi roundabout operates at LOS F, the lowest possible rating, with an average control delay of 300 seconds per vehicle during peak hours. The through movements in the Alkarrada-Aljadiriya direction were identified as the primary cause of capacity constraints. Implementing the proposed geometric design significantly improved performance. For the design year 2037, the modified interchange was projected to operate at LOS B, with average delays reduced by a factor of 20 compared to the existing condition. Even under current 2017 traffic volumes, the proposed design would achieve LOS B with an average delay of only 10.6 seconds per vehicle. Sensitivity analysis confirmed that the design maintains at least LOS D across various traffic distribution scenarios, meeting AASHTO standards for acceptable service. The study concludes that the construction of an underpass for the major through movements, combined with signalization for the remaining intersection traffic, is the most effective solution for alleviating congestion at Ahmed Urabi Square. This approach not only resolves immediate operational failures but also accommodates future traffic growth, ensuring efficient traffic flow and reducing economic and environmental impacts associated with congestion.

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• intersection design