TEKNIK DERGI, cilt.24, sa.4, ss.6479-6504, 2013 (SCI-Expanded)
Composition of a traffic flow is one of the most important factors which effects operations at intersections. The effect of different vehicle types in a flow may be reflected by using passenger car equivalence (PCE) values. In this study, it is tried to determine the effect of heavy vehicles at roundabouts, especially the most common heavy vehicle type of buses at urban traffic. Data of the study are obtained from five different roundabouts in Izmir The results show that when calculating the heavy vehicle factor (f(AA)), different PCE values should be used for minor and major flows. Using the same PCE value for both flows may lead engineers to overdesign or inadequate results. Furthermore it was determined that the effect of heavy vehicles is higher in the major flow when mean speed of major flow is low.