Missoula is getting its first single lane roundabout at the intersection of Higgins - Hill - Beckwith. This is completely different than the current traffic circles that can be found in our towns residential neighborhoods; which are meant to calm traffic at non-controlled intersections.
The roundabout has been under construction for about two months (more here) and is meant to make safer and more efficient a major intersection for traffic going to both the University of Montana and downtown. Pedestrian safety was a major design factor for the reconstructed intersection as the old intersection provided no safe or marked way for pedestrians to cross.
Roundabouts like the one about to open have been proven in numerous studies (here and here) have shown that roundabouts can reduce traffic accidents at intersections by anywhere from 30% to 70% depending on the prior intersection environment; this is mostly due to decreased speeds and the elimination of traffic crossing paths.
Roundabouts also reduce congestion, wait times at intersections, CO2 emissions, decrease fuel consumption and can reduce lifetime maintenance costs by up to 90%.