Routing penalties/Controlling U-turn penalties: Difference between revisions View history

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(→‎{{@|Preventing median U-turns}}: simplification. set instead of assess or apply (consistently). Use of segments "A" "B" and "C" instead of "incoming" "median" and "outgoing")
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=== {{@|Median U-turn penalty}} ===
#REDIRECT [[USA:Routing penalties/Controlling U-turn penalties]]
{{anchor|Avoiding U turns|Avoiding U turns in box and partial box intersections}}
{{Mbox|type=forum|text=For the latest discussion on this section please visit [http://www.waze.com/forum/viewtopic.php?t=108731 the wiki forum thread].}}
 
[[File:U-turn_Roads.png||360px|right]]
The Waze routing algorithm sets a [[Routing penalties#Road_configurations|penalty]] for some double-left or double-right turns. This can prevent U-turns at H-style intersections on divided and parallel roads.
 
==== {{@|Preventing median U-turns}} ====
A large U-turn penalty is set for a double-left or double-right turn when '''''all three''''' of the conditions below are met:
 
# The U-turn involves a reversal of driving direction through 3 segments: <br>A) an incoming segment, B) a single median segment, and C) an outgoing segment
# Segment B is shorter than 15 m (49.21 feet)
# Segment A and segment B are  [[#Checking for parallel segments|within ±5° of parallel]] to each other
<br>
{{Mbox|type=important|text=It is possible for this method to fail to prevent a U-turn when it is the first segment of a route or reroute. If you observe this method to fail when it is implemented properly, please report it in [http://www.waze.com/forum/viewtopic.php?p=994385#p994385 this forum thread]}}
<br>
 
==== {{@|Allowing median U-turns}} ====
 
To allow a double-left or double-right turn through a median segment, break any one of the [[#Preventing median U-turns|above criteria]]. For example:
 
* To allow median U-turns in both directions, break condition #2 by making the median segment longer than 15 m (49.21 ft)
* To selectively allow a U-turn from only one direction, first setup U-turn prevention as you would for both directions. For the side where U-turns are allowed, make the incoming and outgoing segments sufficiently [[#Checking for parallel segments|non-parallel]]. (Tip: consider using a [[Glossary#mDL|Micro-dogleg]] to discreetly tweak the angle without affecting appearance)
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==== {{@|Checking for parallel incoming and outgoing segments}} ====
 
Condition #3 for U-turn prevention requires the incoming and outgoing segments to be within ±5º of parallel to each other. These two segments are considered parallel if their angles with respect to a ''straight'' median segment sum to 180±5º (i.e, between 175º and 185º).
 
Angles can be easily checked with the [[Scripts#WME_Junction_Angle_info|Junction Angle Info]] script add-on, which can be set to report absolute angles or [[How_Waze_determines_turn_/_keep_/_exit_maneuvers|turn angles]] ("departure"). For the purpose of determining parallelism, summing either measurements will work.
<br>
[[File:U-turn_Parallel_Check_Straight.png||center]]
 
 
However, if the median segment has geometry nodes and is not straight, it cannot be used as a reference. In this case, temporarily add a straight segment to the same junctions as the existing curved median. Check the angles using this straight median and delete when done.
<br>
[[File:U-turn_Parallel_Check_Curved.png]]
<br>
 
==== {{@|Common mistakes}} ====

Latest revision as of 18:18, 8 January 2022

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