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Model Inventory of Roadway Elements – MIRE, Version 1.0

136. Circular Intersection — Inscribed Diameter

Definition: Distance between the outer edges of the circulatory roadway of a circular intersection.

Attributes: Feet

See Figure 9 for additional detail.

Priority: Critical

HPMS/Tool Requirements: None

Illustration shows a circular intersection (roundabout) with several details. Inscribed diameter is indicated by an arrow that spans the diameter of the circle, between the outer edges of the paved circular surface and through the central island. Other elements shown include the entry and exit widths for an approach leg (measured at the point of intersection with the circulatory lane), circulatory lane width, splitter island width (measured at the intersection with the circulatory lane), crosswalk location (measured from the yield line to the crosswalk line), and entry and exit radii (measured between two adjacent approach legs).

Figure 9. Illustration of Circular Intersection.

Page last modified on October 15, 2014.
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Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000