This slide shows a comparison of the number of conflict points between vehicles.
	On the left, you can see the traffic signal has 32 conflict points between vehicles.  While the roundabout on the right has only 8 conflict points.
	The elimination of the crossing conflicts eliminates the more severe types of crashes (angle and head on) that occur at intersections.  The geometry of the roundabout also reduces the speed through the intersection further reducing the severity of any crashes which may occur.