Factors Affecting Saturation Flow at Signalized Intersections in Addis Ababa
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Date
2011-01
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Addis Ababa University
Abstract
This study was conducted to identify factors affecting saturation flow at signalized intersections in Addis
Ababa. Secondary data collected using headway method, synchronous method and asynchronous
method were used for the analysis. The data consisted of headways, number and type of vehicles,
number of lanes in an approach, approach grade, green time length of a signal, lane width, number of
pedestrians crossing vehicle flows, and percentage of large buses that made vehicle flows in a lane (as
derivative information).
Lane wise saturation flows were determined using headway ratio method, synchronous regression
method and asynchronous reg ression method. Passenger car equivalents for each class of vehicles were
also estimated.
The saturation flow estimated from the th ree methods was regressed on the independent variables.
Based on the coefficient of determination, synchronous regression method was found to have better
explanatory power. Slope of an approach and number of pedestrians crossing vehicle flows were found to
be significant factors affecting saturation flow of veh icles at signalized intersections when the
synchronous method was applied to estimate saturation flows. Therefore, attention should be paid to
approach grade while designing new road intersections and modifying existing ones and pedestrians
should be given sufficient awareness so that they do not disrupt traffic flow during green phase of traffic
signal.
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Factors Affecting Saturation, Flow at Signalized Intersections