User:TerryPurdue/Junction Style Guide/Interchanges

Diverging Diamond Interchange (DDI)

See also: Diverging Diamond Interchange article on Wikipedia.

Diverging diamond interchanges (DDI) are a type of diamond interchange in which the two directions of traffic cross to the opposite side as they pass over/under the limited-access roadway.

This type of interchange is unusual, in that it requires traffic to briefly drive on the opposite side of the road from what is customary for the jurisdiction.

Segment Directionality

All ramp and surface street segments are set as one-way.

At-Grade Intersections

Junctions

As with all at-grade intersections in Waze, all DDI at-grade intersections are modeled with junction points, including the two signaled intersections where opposing directions of traffic "cross over" each other.

Turn Restrictions

Overview

Outer Surface Road Intersections:

Disable the SINGLE turn from the one-way segment carrying traffic exiting the DDI to the one-way segment carrying traffic entering the DDI at both outer surface road intersections, for a total of two disabled turns.

Inner Surface Road Intersections:

Disable the TWO turns from one-way segments to the segments carrying traffic the opposite direction at both inner surface road intersections, for a total of four disabled turns.

Ramps

DDI's contain exactly 12 one-way ramp segments.

• Four one-way on-/off-ramp segments servicing the limited-access roadway
• Eight one-way feeder ramp segments, two feeder ramps per on-/off-ramp, carrying traffic from both directions of travel along the surface road to/from the on- and off-ramps.

Elevations

Elevations are set to reflect the limited-access road passing over/under the DDI, and that all segments that connect at at-grade intersections have identical elevation.