Left turns are prohibited at the main intersection, which therefore requires only a two-phase signal. Vehicles yield upon entry to the roundabout. If the roundabout has only two entrances, the entry from the main intersection does not have to yield.
The roundabout diameter, including the center island and circulating roadway, varies from 90 feet to 300 feet depending on the speed of traffic on the approaches, the volume of traffic served, the number of approaches, and the design vehicle.
This configuration would reduce delay for the arterial street, increase capacity, and reduce the number of stops required. The primary problem with such a configuration is driver disregard for the left turn prohibition at the main intersection.
As yet no agency has designed a complete bowtie road junction.
- Jonathan Reid, P.E.: Unconventional Arterial Intersection Design July 2004, P. 66-67, retrieved on 9 February 2013
- Unconventional Left-Turn Alternatives for Urban and Suburban Arterials An Update (pdf)
- Eliminating Left-Turns at a Signalized Intersection With The Use of Nearby Roundabouts (pdf)
- Guidance on the Safe Implementation of Unconventional Arterial Designs (pdf)
- FHWA-HRT-04-091: Signalized Intersections: Informational Guide
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