User:TerryPurdue/Junction Style Guide/Interchanges View history

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

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.

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.

@@ Line 1: / Line 1: @@
-== 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.
+[[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 ===
-('''TODO''': add zoomed in pic of one of the at-grade intersections)
-All DDI's contain exactly 12 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.]]''
-* Two "outer surface road" intersections, where drivers on the surface road enter/exit the DDI
+=== At-grade intersections ===
-* Two "inner surface road" intersections, where the two directions of travel along the surface road "cross over" each other at signaled intersections.
-* Four "offramp" intersections, where drivers use ramps to exit the limited-access road and enter the DDI
-* Four "onramp" intersections, where drivers transition from the surface road segments inside the DDI onto ramps that lead to the limited-access road
 ==== Junctions ====
-All 12 interchanges are modeled with a junction point in the Waze map.
+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''':
-('''TODO''': add zoomed in pic of the disabled turn at an outer surface road intersection, with the segment in question highlighted)
-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''':
-('''TODO''': add set of zoomed in pics for the disabled turns at an outer surface road intersection, one pic per segment with disabled turns)
-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.
-'''Ramp Intersections''':
+==== Turn restrictions ====
-None of the turns between ramp and surface street 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 between the DDI and 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, each one dedicated to one of the two directions of travel along the surface road
+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 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.

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