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== Diverging Diamond Interchange (DDI) ==
== Diverging diamond interchange (DDI) ==
 
[[File:JSG-Interchanges-DDI-Overview.png|800px]]


''See also:'' [https://en.wikipedia.org/wiki/Diverging_diamond_interchange Diverging Diamond Interchange] article on Wikipedia.
''See also:'' [https://en.wikipedia.org/wiki/Diverging_diamond_interchange Diverging Diamond Interchange] article on Wikipedia.
[[File:DDI Example Dupont.png|thumb|845x845px|none]]
Diverging diamond interchanges (DDI) are a type of diamond interchange in which the two directions of traffic cross one another on each side of a limited-access roadway. A DDI may pass over or under the limited-access roadway.


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. However, the design of the Diverging Diamond Interchange controls the driver's line of sight to ensure the cross-over action feels natural and goes unnoticed.
 
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.


=== At-Grade Intersections ===
=== Segment directionality ===
[[File:DDI Example Dupont - traffic flow.png|thumb|848x848px|Flow of traffic within a Diverging Diamond Interchange|none]]
All ramp and surface street segments are set as one-way. If you are creating a DDI along a road which is not divided, divide the road, first. See'' h[[usa:Best_map_editing_practice#Dividing_and_un-dividing_divided_highways|ow to properly divide/un-divide a road.]]''


[[File:JSG-Interchanges-DDI-AtGrade.png|800px]]
=== At-grade intersections ===


==== Junctions ====
==== 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.
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 (inner surface road junctions). A DDI may also have two outer surface road junctions, where the one-way segments transition to two-way road segments.
 
==== Turn Restrictions ====
 
Summary:
 
* ALL turns less than 90 degrees are '''enabled'''
* ALL turns greater than or equal to 90 degrees are '''disabled'''
 
 
Exactly six turns are disabled in a DDI:
 
'''Outer Surface Road Intersections''':
 
[[File:JSG-Interchanges-DDI-OuterRestriction.png|800px]]
 
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''':
 
[[File:JSG-Interchanges-DDI-InnerRestriction-01.png|640px]]
 
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.


'''On-/Off-Ramps''':
==== Turn restrictions ====


None of the turns to, from, or between ramp segments are disabled.
===== Overview =====
There are four junctions in a DDI at which the turn restrictions must be checked - two inner surface road junctions where traffic crosses, and two outer surface road junctions where the road divides/joins on each side of the DDI.[[File:DDI Example Dupont - turn restrictions.png|thumb|871x871px|All restricted turns within a DDI (displayed by using Shift+Z).|none]]


=== Ramps ===
===== Inner surface road junctions =====
[[File:DDI Example Dupont - turn restrictions - inner - 01.png|none|thumb|871x871px]]
[[File:DDI Example Dupont - turn restrictions - outer - 02.png|none|thumb|870x870px]]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.


DDI's contain exactly 12 one-way ramp segments.
===== Outer surface road junctions =====
* Four one-way on-/off-ramp segments servicing the limited-access roadway
[[File:DDI Example Dupont - turn restrictions - outer.png|none|thumb|871x871px]]
* 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.
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.


=== Elevations ===
=== 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.
Elevations are set relative to the limited-access road passing over or under the DDI, with all segments that connect at at-grade intersections having identical elevation.

Latest revision as of 14:38, 18 April 2017

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 one another on each side of a limited-access roadway. A DDI may pass over or 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. However, the design of the Diverging Diamond Interchange controls the driver's line of sight to ensure the cross-over action feels natural and goes unnoticed.

Segment directionality

Flow of traffic within a Diverging Diamond Interchange

All ramp and surface street segments are set as one-way. If you are creating a DDI along a road which is not divided, divide the road, first. See how to properly divide/un-divide a road.

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 (inner surface road junctions). A DDI may also have two outer surface road junctions, where the one-way segments transition to two-way road segments.

Turn restrictions

Overview

There are four junctions in a DDI at which the turn restrictions must be checked - two inner surface road junctions where traffic crosses, and two outer surface road junctions where the road divides/joins on each side of the DDI.

All restricted turns within a DDI (displayed by using Shift+Z).
Inner surface road junctions

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.

Outer surface road junctions

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.

Elevations

Elevations are set relative to the limited-access road passing over or under the DDI, with all segments that connect at at-grade intersections having identical elevation.