Turbo-Roundabouts: a Model to EvaluateCapacity, Delays, Queues and Level of Service

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A turbo roundabout is a particular type of roundabout where entering andcirculating lanes are bounded by traffic signs and by non-mountable curbs. The physicalseparation between lanes, both at entries and on the ring, helps to prevent side collisionscrossing the roundabout. The main advantages of turbo roundabouts are: i) reduction in thenumber of potential conflict points; ii) lower speed of vehicles passing through theintersection; iii) safety conditions at the intersection due to lower risk of side-by-sideaccidents. These aspects make turbo-roundabouts more appropriate than roundabouts whena higher level of safety has to be guaranteed, particularly in presence of relevant pedestrianand two-wheels traffic volumes. Also, in some cases the capacities of turbo roundaboutsare higher than the capacities of conventional roundabouts. This paper presents anestimation of capacity, delays, queues and level of service of turbo roundabouts inundersaturation traffic conditions, considering both vehicular flow and pedestrian stream. Italso examines the geometric parameters in several turbo roundabout layouts and presentsone case study from real world concerning the conversion of existing large diameterroundabout into two linked turbo roundabouts.
Original languageEnglish
Pages (from-to)267-282
Number of pages16
Publication statusPublished - 2012


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