Abstract:
Intersections play a significant role in the road network, where traffic flowing in different
directions crosses each other. The traffic flow at signalized intersections is more complex
under heterogeneous traffic flow characteristics. Traffic-signal controls are commonly used in
several at-grade junctions in urban areas to maximize traffic efficiency and safety by
separating traffic movements in time.
Traffic congestion and excessive delays at intersections is increasingly becoming a severe
problem in developing countries than in the developed world. The objective of this research
was to assess the operational performance of selected signalized intersections in Jimma Town.
Traffic congestion and delays that cause poor traffic performance have negative impacts on
economic productivity, environmental quality, and safety. The signalized intersections at
Jimma Town are experiencing the same scenario. For the objective to be met, the four
congested major intersections (Merkato, Menaharya, Faid Adebabay and Menafesha) were
selected for the study. The traffic data on all approaches to the intersections was collected by
a video camera during the most congested days of the week (Tuesday, Thursday and Saturday).
The traffic volume obtained in different classes of a vehicle has been converted to a uniform
vehicle fleet by the passenger car unit factor. Additionally, the geometric data for the selected
intersections were measured, and signal cycle time and phase sequence were recorded at the
time of field data collection. Data analysis and processing were performed using SIDRA
intersection software to determine the traffic flow condition at the intersection. The
performance measures used to evaluate the intersections were the average delay, degree of
saturation, queue length, capacity and Level of service at the intersection were interpreted.
Based on the findings, all intersections are serving in poor condition with a level of service F,
v/c ratio greater than 1.0 and the average delay experienced was 338.9s for Merkato, 385.7s
for Menahariya, 251.8s for Faid Adebabay and 295.3s for the Menafesha intersection. Based
on sensitivity analysis, base saturation has reduced delay by 20–23%. Heavy vehicle restriction
reduces delays by 8–20% for all intersections. Lastly, a basic saturation flow study, heavy
vehicle restrictions and a regular traffic volume count database are the major
recommendations forwarded
