Determination of Basic Saturation Flow Rate in Istanbul

In traffic signal operations, the saturation flow rate is one of the key parameter for the calculation of signal timing. The saturation flow rate for different type of roads is simply calculated by multipliying the basic saturation flow rate, which is determined for predefined road type and flow condition with side factors. The aim of this study is to calculate the basic saturation flow rate in Istanbul. This calculation is based on the evaluation of vehicles’ headways at signalized intersection. The field study is conducted at 23 signalized intersections having basic conditions and 18,311 vehicle headways are analyzed. The initial calculations in this study are the determination of the saturation flow region, in other word from which vehicle in the queue does the saturation flow start. It is found that the saturated headway starts from second to eighth vehicle while the saturated headway is determined as 1.9 seconds, which is equivalent to 1,894 passenger cars unit per hour as saturation flow rate.