A Comprehensive Through Lane Saturation Flow Rate Model for Signalized Intersection by Considering Illegal Crossing Pedestrian Effect at Selected Intersections in Addis Ababa
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Date
2025-06
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Addis Ababa University
Abstract
One significant element influencing urban traffic performance networks is signalized
intersections. It can guarantee safe and efficient traffic flow through the crossings and optimize
their capacity.
Researchers have been examining signalized junction capacities for a long time. However, the
pedestrian effect has not been well studied. Two perspectives are used to analyze the effects of
pedestrians: 1) Traffic flow is disrupted by pedestrians; 2) Speed and saturation flow rate are
reduced as a result of pedestrian interference.
One of the crucial aspects of analyzing the capacity of signalized junctions that is influenced by
several circumstances is saturation flow rate.
Geometric conditions, traffic conditions, driver conduct, traffic light timing, gradient direction,
number of lanes, lane width, volume and kind of turning actions, and pedestrian movement are
some of the effective aspects that HCM identifies as determining saturation flow.
Walking is a popular form of transportation in Addis Ababa, and people who cross the street
when green traffic light is on have an impact on traffic flow.
We chose five Addis Ababa signalized crossings to examine how pedestrians affect signal
capacity. St. Estifanos, Banko de Roma, Ayer Tena, Jemo Michael, and Saris Abo. Their current
functional status, being four-legged, high pedestrian flow, High traffic volume, least interference
to entry and exit traffic due to parking activities were the criteria for their selection.
Video graphic method was used to gather pedestrian and traffic data from the field. The hours of
8:00 AM to 9:00 AM and 3:00 PM to 4:00 PM were used to gather traffic data.
To develop a suitable saturation flow equation for estimating capacity and designing traffic
infrastructure for heterogeneous traffic, the heterogeneous traffic must be transformed into
homogeneous using a common unit, called the PCU.
The dynamic PCUs have been computed in this study, which takes vehicle size and speed into
account as key variables for PCU component estimation. The Method adopted in this thesis work o generate a model equation to calculate PCU is Speed-Area method which is developed by Dr.
Satish Chandra, according to Chandra’s method (1)
This study presents a saturation flow rate analysis of selected Addis Ababa's signalized crossings
under mixed traffic situations. In order to collect information on traffic volume and speed on city
roads, a video graphic technique was used to determine the saturation flow.
The headway which is the amount of time that passes between successive cars crossing the stop
line had calculated and then 3600 divided by this headway to get the saturation flow rate.
Measurements of saturation flow rates generally show 2.47% - 29.53% lower values than those
currently used in the Highway Capacity Manual. The saturation flow rates at the local crossings
will be overstated if HCM's suggested value is implemented in study intersections; the presence
of pedestrians didn’t show significance in through lane saturation flow rate. A general model for
the saturation flow rate analysis should have been created in the spot while we design and
maintain an intersection in Addis Ababa.
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Keywords
signalized intersection, saturation flow rate, mixed traffic flow, and pedestrian