Evaluation of Vehicle Time Delay at Selected Signal Controlled Intersections in Addis Ababa

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Addis Ababa University


There are two types of traffic facilities, interrupted and uninterrupted flow facilities. The interrupted flow facility incorporates fixed external interruptions in their design and operation. The most frequent and operation only significant external interruption in interrupted flow facility is a traffic signal. Traffic signals are one of the most effective and flexible active controls of traffic flow. They are widely used in several cities worldwide. The conflicts arising from movements of traffic in different directions are addressed by time-sharing principle. Besides, its controller unit is either pre-timed or actuated control. Pre-timed control consists of fixed sequence of phases displayed in a repetitive order. Actuated control consists of intervals that are called and extended in response to vehicle detectors. Traffic congestion is experienced in urban areas due to economic and social developments. Addis Ababa is one of the places with rapid economic development which exhibit a higher amount of traffic congestion problem at different intersections and the urban street of the road. Vehicle delay is the most important parameter used by transportation professionals in evaluating the performance of a signalized intersection. In this research, three pre-timed signalized intersections in Addis Ababa are selected based on data availability and discussion with Addis Ababa city administration transport bureau as they experience congestion. The objective of this paper is evaluating vehicle delay in Addis Ababa at selected Intersection and evaluating selected intersection by sensitivity analysis using highway capacity manual and SIDRA intersection software. To achieve the objective of the research, the collection of primary and secondary data was conducted. The traffic volume data were collected from Addis Ababa city administration transport bureau. The count was conducted for five days and twelve hours with a fifteen-minute interval of time. Data on geometric elements signal timings and phasing were measured through field survey and Google map. Peak hour volume is used for analysis after determining the peak hour of the intersections. As per the analysis of results, all intersections are serving in poor condition of level of service F, vehicle per capacity ratio greater than one and the average delay experienced 126 sec for Jacros, 431.4 sec for Lebu and 710.4 sec for imperial intersection. From sensitivity analysis, base saturation has reduced delay by 29.53% at Lebu, 39.12% at Jacros and 26.87% for Imperial intersection. Heavy vehicle restriction reduces delay by 46.05% at Lebu, 57.14% at Jacros and 10.78 % at Imperial intersection in addition adding one through lanes reduces delay by 47.72% at Lebu, 68.01% at Jacros and 34.41% Imperial intersection as compared to other parameters.



Signal Controlled Intersections, Vehicle Time Delay