Flower roundabouts: estimation of capacity and level of service

The research work on road junction geometry, carried out in European research centres, has recently allowed to design new road intersection types which are of undoubted interest, especially in terms of traffic functionality and safety. Among the most interesting solutions there are such schemes as spiral, turbo and flower roundabouts, which are similar to traditional roundabouts. Although these solutions provide a traffic travels counterclockwise around a central island and in which entering traffic must yield to circulating traffic, the newly designed schemes generally offer modes of traffic flow regulations which highly differ from those used in conventional roundabouts. Of considerable interest are flower roundabouts, in which right-turn manoeuvres do not conflict with the circulating flow. The main objective of this paper is to examine the geometric aspects of flower roundabouts, as well as to propose a model for the estimation of the capacity and levels of service.