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Abstract

Intersections are among the most critical elements of highway networks because they directly influence traffic efficiency, capacity, and safety. This study evaluates improvement alternatives for Al-Kansaa's three-leg intersection in Iraq, which currently experiences severe traffic congestion and operates at Level of Service (LOS) F. Traffic volume surveys and geometric data were collected and analyzed using Highway Capacity Software (HCS2010), while Autodesk Civil 3D was employed to develop and evaluate four geometric improvement alternatives. The existing intersection analysis indicated an average control delay of 398.66 s/veh, corresponding to LOS F. The first improvement proposal, which involved adding a lane to the southbound approach, reduced the average delay to 165.67 s/veh; however, the intersection continued to operate at LOS F, indicating that geometric widening alone was insufficient. Therefore, three grade-separated interchange alternatives were developed and assessed based on operational performance, geometric feasibility, land-acquisition requirements, and constructability. Among the proposed alternatives, the interchange incorporating two bridges and a roundabout was identified as the most suitable solution because it provides smoother traffic operations, minimizes land acquisition, reduces construction constraints, and preserves the operational performance of the major roadway. The findings demonstrate that comprehensive geometric redesign is more effective than minor geometric modifications for improving heavily congested three-leg intersections and may serve as a practical reference for similar intersections in developing countries. The novelty of this study lies in the integrated evaluation of four alternative intersection improvement proposals by combining traffic operational performance, geometric design, constructability, and land-acquisition considerations within a single decision framework for a real-world three-leg intersection.