الفهرس 
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Abstract
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 thesis 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.