Assessment of operational performance of the coordinated signalized Intersections along John Babiiha Road

Abstract

Traffic congestion is defined as a condition of traffic delay (when the flow of traffic is slowed below reasonable speeds) because the number of vehicles trying to use the road exceeds the traffic network capacity to handle them. Intersection signalization is one of the more cost- effective ways to remedy the traffic congestion predicament. The basic function of signalized intersections is to sequence right-of-way between intersecting streams of roadway users at points of conflict. Intersections in close proximity can be signalized to form network or a corridor of signalized intersections. Signalized intersections may facilitate smooth traffic flow but they cause delay at intersections, thus when in close proximity the cumulative delay is excessive. Therefore, there is need to coordinate signalized intersections in networks or at successive intersections on arterial of spacing (100 to 800) meters. Signal coordination enhances certain movements and reduces overall delay at signalized intersections known as control delay. Due to the variations in traffic demand with time in large urban areas, the periodic assessment of operational performance of coordinated signalized intersections is a necessity. A case study of the newly rehabilitated and signalized John Babiiha Road that had four newly signalized intersections along the road that had signal spacing ranging between 100m to 650m. We assessed the performance of the selected coordinated signalized intersections in enhancing the movement of the though traffic stream along the arterial. The performance was evaluated through the determination of LOS of the road. The LOS was determined on the basis travel speed and control delay of the through traffic stream. We collected traffic, geometric and signalization data from the road and the signalized intersections. We carried out theoretical calculations manually and also used spreadsheets to determine various parameters i.e., capacity, control delay, running time and travel speed of the facility. The results obtained an overall LOS F of the facility. Findings from the study attributed the poor level of service majorly to the inadequate signal timing plan used on the various intersections on the road. Therefore, the signalized intersections require signal retiming with emphasis on coordination techniques to enhance the through movement.