Investigation of the effects for motorcycles on the saturation flow rates at signalized intersections.

Abstract

The saturation flow rate is an important parameter for the design of signalized intersections and capacity analysis. It largely depends on the vehicle mix in the traffic stream. The traffic composition in Kampala may largely be classified as mixed due to the high proportions of motorcycles and this makes it very different from other areas of the country. In the developing countries like Uganda, motorcycles are a major transportation mode, but very little attention has been paid to their effects on the traffic flow. In this study, the Saturation flow rates, and passenger car unit values were determined at two signalized intersections for both the right turn and through movements. Traffic data was obtained at three signalized intersection approaches/arms at traffic peak hours to ensure saturation flow and queuing conditions using the video method. The videos were played and analyzed on a computer and the traffic flow manually classified using the UNRA vehicle classification sheet. Motorcycles were further classified into 3 categories which include, In front of Lead passenger car, In the vehicle lateral gaps and in the vehicle queue. The results of the research indicate that motorcycles significantly affect the Vehicle Saturation flow, and it should be taken into account in geometric design and operation of signalized intersections