This paper examines the road safety effects of roundabouts built in Flanders between 1994 and 2000. While the overall effect is positive (39% reduction of injury accidents), the results vary considerably with the speed limit on the main and adjacent road (the higher, the more effective) and the pre-roundabout signalization of the intersection (32% reduction with traffic lights versus 44% without). However, microscopic analysis reveals that roundabouts are not always effective. Serious injury accidents are estimated to increase by 117% on 70 km/h x 50 km/h intersections equipped with signalization before the roundabout. The number of injury accidents involving vulnerable road users is also found to increase (28%) on 50 km/h x 50 km/h junctions that were originally signalized. Moreover, the vulnerable road user is more likely to get fatally or seriously injured. Therefore, it is concluded that traffic lights protect vulnerable road users more effectively than roundabouts, which, in turn, are superior to intersections without signalization.