There are two reasons that the Town and the Tennessee Department of Transportation (TDOT) like the roundabout solution for the intersection of Atoka-Idaville and Rosemark Roads.
The first reason a roundabout is being considered is safety. A roundabout is a dramatically safer intersection when compared to a traditional, stop sign or stop light controlled intersection. There are three types of traffic conflict points that can exist in an intersection: diverging, merging and crossing. Conflict points are typically where accidents occur in an intersection.
Diverging conflict points tend to result in rear-end fender bender accidents where a car approaching the intersection impacts the rear bumper of the car ahead.
Merging conflict points tend to result in nose-to-nose accidents where the front of the driver side of one vehicle impacts the front of the passenger side of the other vehicle.
Crossing conflict points are typically the most dangerous type of impact – typically called a "t-bone" accident where the front of one vehicle impacts the side of the other vehicle in a nearly perpendicular fashion.
As it exists today, there are 9 points in the intersection where traffic intersects – 3 of each of the conflict point types : diverging, merging and crossing. In a three-legged roundabout, there are 6 conflict points – 3 diverging and 3 merging. In addition to a 33% reduction in traffic conflict points, the most dangerous type of conflict point – the crossing conflict – is completely eliminated.
The below diagram is from the Federal Highway Administration's report on roundabouts - issued June 2008 - showing the reduction in conflict points for a three-way intersection.
Roundabout accidents, when they do occur, tend to occur at lower rates of speeds and with significantly less risk of fatality. In fact, NYDOT Transportation Project Manager Ken Kuminski recently commented about roundabouts installed in Hamburg, NY that, "accidents in them need a tow truck, not an ambulance."