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

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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 conditions]]. For example:
 
* To allow median U-turns in both directions, break condition #2 by making the the median segment B longer than 15 m (49.21 ft)
* To allow a U-turn from only one direction, first set up U-turn prevention for both directions. Then, to allow U-turns on one side, change the angles for segment A and segment B so they are [[#Checking for parallel segments|not parallel]]. A [[Glossary#mDL|micro-dogleg]] can be used to change the angle without changing the appearance of segment.
<br>
 
==== {{@|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. This is checked by using a ''straight'' median segment and the [[Scripts#WME_Junction_Angle_info|Junction Angle Info]] (JAI) browser extension to measure the angles. JAI may be set for absolute or [[How_Waze_determines_turn_/_keep_/_exit_maneuvers|turn angles]]; either setting is OK.
 
If segment B is straight, measure the angles between segment A and segment B, and between segment B segment C. If the sum of these angles is between 175º and 185º, segment A and segment B are considered parallel.
<br>
[[File:U-turn_Parallel_Check_Straight.png||center]]
 
If segment B has geometry nodes it is not straight. It cannot be used to measure the turn angles. Instead, draw a straight segment to the same junctions used by segment B. Check the angles using this straight median. Delete the straight median afterwards
<br>
[[File:U-turn_Parallel_Check_Curved.png]]
<br>
 
==== {{@|Common mistakes}} ====

Latest revision as of 18:18, 8 January 2022

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