Different models of saturation flow in traffic dominated by motorcycles

Motorcycle traffic has attracted little interest in the past, despite the reported increase in motorcycle ownership in many countries. Saturation flow and vehicle equivalence factors such as PCU values are two of the most important parameters characterising the traffic flow at signalised junctions. The investigation of these parameters facilitates a better understanding of traffic dominated by motorcycles. This paper introduces a new method to study the variation of saturation flow and vehicle equivalence factors. MCU values have been applied instead of the conventional PCU values. Five regression models were derived to describe the variation of saturation flow in three traffic compositions, including (1) motorcycles and straight-on cars, (2) motorcycles and cars making three movements (right, left and straight-on) and (3) all vehicle types making three movements. The paper also assesses the difference between two approaches of counting vehicles: one based on 4s periods during green time; the other based on the signal cycle. MCU values were estimated for different vehicle types making different turning movements.