Determination of the performance of intersections by using hypothetical or default values without regional observations may lead to unrealistic results. The main goal of this study is to investigate the ideal saturation flow value which is one of the most important parameters in predicting capacity of signalized intersections. In this study, values for ideal saturation flow and parameters of various correction factors were recommended by using the observations obtained from 10 signalized intersections from Izmir, Bursa and Denizli provinces. Analyses have shown that, ideal saturation flow value for signalized intersections can be a rather low value such as 1720 passenger cars/hr/lane, dropping to 1634 veh/hr/lane for signalized traffic roundabouts. Furthermore, passenger car equivalence values for heavy, right turning and left turning vehicles were also suggested.