Roads and Bridges - Drogi i Mosty
11, 3, 2012, 215-231

Turbo-roundabouts as an alternative to standard roundabouts with the circular centre island

Ryszard J. Grabowski Mail
Bialystok University of Technology, Faculty of Civil and Environmental Engineering


The paper presents the process of shaping turbo-roundabouts. A classic road roundabout is formed around the central island in the shape of the circle. The central island of the turbo-roundabout will be created when the circle is divided into two semicircles and displaced along the axis of the roundabout by the width of the traffic lane. This shift causes that vehicles entering the interior lane, cross the centre line and are automatically situated in the exterior lane. The paper presents the central island shaping with the use of other curves, including an ellipse and the spiral of Archimedes. Moreover, the principle of creating the circulating lanes of roundabout using the spiral of Archimedes and delineating such roundabout in the terrain are described in the paper.


ellipse, roundabout, spiral of Archimedes, turbo-roundabout

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Turbo-roundabouts as an alternative to standard roundabouts with the circular centre island

Grabowski, Ryszard J.. Turbo-roundabouts as an alternative to standard roundabouts with the circular centre island. Roads and Bridges - Drogi i Mosty, [S.l.], v. 11, n. 3, p. 215-231, apr. 2012. ISSN 2449-769X. Available at: <>. Date accessed: 26 May. 2024.