In recent years, Cowan M3 distribution model started to be used widely, around the world by traffic engineers and researchers for capacity and performance analysis of roundabouts and unsignalized intersections. However, some differences between the usage and application in different countries are observed. This is mainly because of the difference between drivers' behaviors. In this study, the present applications of Cowan M3 distribution and its parameters are discussed and more appropriate parameters that will define Turkish drivers' behavior are searched. (C) 2002 Elsevier Science Ltd. All rights reserved.