The Effect of Small Vehicles’ Modal Shifting to Bus on The Performance of Some Selected Roundabouts in Addis Ababa
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Date
2024
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Addis Ababa University
Abstract
Roundabouts are the circular island for vehicles movement from different direction to change movement directions, paths and for crossing by counterclockwise movement around the circle. The imbalanced increase traffic volume will result traffic congestion. The main determinant for performance is traffic volume and the geometry of the roads. Many intersections and roundabouts in Addis Ababa city suffer from poor traffic management, leading to congestion and delays. To address this issue, the Addis Ababa Traffic Management Office has converted most roundabouts into signalized intersections. Additionally, the Ministry of Transport has developed a 10-year plan aimed at increasing the share of urban mass transport services from 34% in 2020 to 70% in 2030. This plan is expected to greatly improve the efficiency and quality of transportation in the city. On this study the performance analysis for the selected areas was performed using PTV Vissim 9 software program. To evaluate the performance of roundabouts, three different approaches were followed: PCU modal shift, unit change modal shift, and carpooling modal shift. The result of the analysis on the baseline scenario for Urael, Lamberet and Salitemeheret roundabout is LOS F, F and F respectively. Then the LOS for Urael and Lamberet roundabout upgraded to LOS B and E respectively and still LOS F for Salitemeheret roundabout with the PCU modal shift path and the LOS of those three roundabouts changed to LOS B, F and F respectively with unit change shift and carpooling modal shift paths. Based on the evaluation results of the Urael roundabout, the vehicular delay time in the baseline scenario was 51.73 seconds. However, in the modal shift scenario, the vehicular delay time ranged from the highest of 51.73 seconds to the lowest of 13.45 seconds and the upgrade was a result of 74% delay reduction from baseline scenario. Similarly, at the Lamberet roundabout, the vehicular delay time was 78.87 seconds in the baseline scenario while in the modal shift scenario; it varied from the highest of 88.90 seconds to the lowest of 42.39 seconds and the upgrade was a result of delay reduction with 46% from the baseline scenario. Lastly, at the Salitemeheret roundabout, the vehicular delay time in the baseline scenario was 92.54 seconds but in the modal shift scenario, it ranged from the highest of 92.54 seconds to the lowest of 27.80 seconds and the upgrade was a result of delay reduction with 70% from the baseline scenario. When the LOS upgrade the travel time was decreased, vehicular traveling speed, queue length, vehicles stop, fuel consumption and the emission was decreased. Finally, this research has significant to determine the preferable modal shift and it will provide information for Ministry of Transport, Traffic Management Office and other concerned group.
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Level of service (LOS), Congestion, Travel time, travel speed and Queue length