This study deals with the operational efficiency of roundabout. The objective of this study is to comparatively analyze the efficiency (average delay time and fuel consumption) at 3-legged roundabouts, In pursuing the above, this study gives particular attention to analyzing the 240 scenarios consisted by entering volume (20 cases), directional ratio (3 cases), roundabout type (2 cases) and traffic simulation program (2 cases), In this study, aaSIDRA and VISSIM simulation programs are used. The main results are the followings. First, the average delay time analyzed by aaSIDRA was evaluated to be more than that by VISSIM. Second, the fuel consumption analyzed by VISSIM was evaluated to be less than that by aaSIDRA. Finally, aaSIDRA in 3-leg 1-lane roundabout and VISSIM in 3-leg 2-lane roundabout were analyzed to have more volume.