Concept of Rotary Intersection

Rotary intersections or roundabouts are special form of at-grade intersections laid out for the movement of traffic in one direction around a central traffic island. Essentially all the major conflict at an intersection namely the collision between through and right-turn movements are converted into milder conflict namely merging and diverging. The vehicles entering the rotary are gently forced to move in a clockwise direction in orderly fashion. They then weave out of the rotary to the desired direction. In one sense, Rotary intersections (or Roundabouts) can be considered as a form of channelized intersection in which vehicles are guided onto a one-way roadway and required to move in a clockwise direction about a central island. At one time, the rotary intersection was considered to be the answer for all the problems associated with intersections. In fact, the rotary intersections have particular advantages and disadvantages, and the decision as to whether a rotary should be used at any individual location requires an understanding of these. Where roundabouts are properly used and designed, the efficient flow of traffic is promoted by the orderly movement of vehicles about the central island. There is only minor delay to traffic due to speed reductions and no delay, at all, due to stopping.