New Type of Roundabout: Roundabout with “Depressed” Lanes for Right Turning – “Flower Roundabout”

Abstract

ABSTRACT

Traffic Efficiency Evaluation of Elliptical Roundabout Compared with Modern and Turbo Roundabouts Considering Traffic Signal Control

“…The capacity of signalized star roundabout (three-leg) was larger than unsignalized star roundabout; however, signalized star roundabout had longer delay time. Tollazzi et al [23] introduced a new type of roundabout with depressed lanes for right turning (the flower roundabout). This kind of roundabout combined positive characteristics of the normal and turbo roundabouts.…”

Right-turn Bypass Lanes at Roundabouts: Geometric Schemes and Functional Analysis

“…The additional right-turn slip lanes are also used to configure turbo roundabouts (Turborotondes -CROW, 2008;Fortuijn, 2009) and flower roundabouts (Tollazzi et al, 2011;Al-Ghandour et al, 2012) (see Figures 1b and 1c). In flower roundabouts actually the geometry and performance are characterized by slip lanes at each leg (Tollazzi et al, 2011).…”

“…The additional right-turn slip lanes are also used to configure turbo roundabouts (Turborotondes -CROW, 2008;Fortuijn, 2009) and flower roundabouts (Tollazzi et al, 2011;Al-Ghandour et al, 2012) (see Figures 1b and 1c). In flower roundabouts actually the geometry and performance are characterized by slip lanes at each leg (Tollazzi et al, 2011). In urban and sub-urban areas, with bicycle and pedestrian activity, a right-turn bypass lane should be implemented only where needed because the entries and exits of bypass lanes can increase conflicts with pedestrians, bicyclists and with merging on the downstream leg.…”

Geometric design of turbo roundabouts

“…Previous studies conducted on turbo roundabouts [8][9][10][11][12][13][14][15] were mainly based on evaluation of their performances (capacity, delays), and environmental, economic and safety benefits, in regard to single-lane, standard multilane, flower and target roundabouts. Turbo roundabout geometric design was considered in a number of other studies [1, 16÷19], which were generally focused on analysis of Dutch turbo roundabout geometry and presentation of new design approaches.…”

“…Most of them are located in the Netherlands (302), a country where this specific roundabout layout was developed, and where first turbo roundabouts were built [7]. Apart from the Netherlands, countries with a notable number of turbo roundabouts are Poland (35), Germany (11), Slovenia (11), Czech Republic (10) and Hungary (7).…”