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Fixed JB rank error (was 5, now using Rank template) in "Allowing median U-turns" section
=== {{@|Controlling U-turns}} ===
{{anchor|Avoiding U turns|Avoiding U turns in box and partial box intersections}}
{{Mboxhatnote|type=forum|text=This article discusses double-turn U-turns. For standard one or two segment U-turns, adjust the latest discussion on this section please visit [[Interface_guide#Junction_Arrows|junction arrows]].}}{{ForumLink|forum= the wiki forum thread|<nowiki>[Page Update].Intersections / U-turns under 15m</nowiki>|section=yes}}{| style="float: right; width: 360px; border: 0px;text-align: center; line-height: 1; font-size: small;"|-| [[File:U-turn_Roads.png||360px|right]]|- | style="padding-bottom: 20px; padding-left:10px;" |''Note:'' The road types displayed in the images might not match the standards for where you edit. Please check your local wiki and with local experts to learn the correct road type to use for '''median segments''' in your area.|}The Waze routing algorithm sets has a method of [[Routing penalties#Road_configurations|penaltypenalizing]] for some double-left or and double-right turns. This can prevent U-turns at H or # style intersections on divided and parallel roads. It is useful for preventing the sequence of two turns that would make up the U-turn, while still allowing the individual turns. However, if either of the two turns making up the U-turn is illegal or impossible, disallow that turn instead. The U-turn will then not be routed, and the following penalty does not matter. 
==== {{@|Preventing median U-turns}} ====
# '''Three segments''': The U-turn is a reversal of driving direction through three segments: <br>an incoming segment&nbsp;(A), a single median segment&nbsp;(B) and an outgoing segment&nbsp;(C).
# '''Short median''': The median segment&nbsp;(B) is shorter than {{:Routing_penalties/U-turn_minimum}}.<br>''As a safety margin, leave a 1 m buffer zone by using equal to {{:Routing_penalties/U-turn_minimum|less}} or less.''
# '''In/out parallelism''': The in and out segments (A&nbsp;and&nbsp;C) are [[#Checking for parallel incoming and outgoing segments|within ±5° of parallel]] to each other.
{{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 it immediately follows a reroute. If you observe this method to fail in other situations when it is implemented properly, please report it in [ this forum thread]}}
==== {{@|Allowing median U-turns}} ====
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To allow median U-turns in both directions, break condition #2 by making the median segment&nbsp;(B) {{:Routing_penalties/U-turn_minimum|greater}} ''or longer''
To allow a double-left or doubleU-right turn through from only one direction, first setup the median segmentintersection to allow U-turns in both directions. Then, break any one of the add a [[#Preventing median Junction Box]], and restrict the prohibited U-turnsturn route. A rank {{Rank|jb}} user or above conditions]]is required to install a Junction Box. For example: * To allow median {{mbox|text=Previously, unidirectional U-turns in both directions, break turn prohibition on a divided road was set up by breaking condition #2 by making 3 of the U-turn prevention mechanism through the median segment&nbsp;(B) use of a [[Glossary#mDL|micro-dogleg]]. {{:Routing_penalties/U-turn_minimumAs of|greater2017}}, Waze staff has expressed a preference that map editors use Junction Boxes in these situations.}} ''or longer''<!-- OLD INFORMATION * To allow a U-turn from only one direction, first set up U-turn prevention for both directions. Break condition #3 on the side where U-turns are allowed. Increase or decrease the angles so that the in and out segments (A and C) are [[#Checking for parallel incoming and outgoing segments|not parallel]]. A [[Glossary#mDL|micro-dogleg]] can be used to change the angle without changing the appearance of the segment.<br>[[File:U-turn selective Uturn prevention.png|center]]-->
The in and out segments (A&nbsp;and&nbsp;C) are considered parallel if the sum is {{font color|red|between 175º and 185º}}.
{| style="border: 0px;text-align: center; line-height: 1; font-size: small;"
| [[File:U-turn_Parallel_Check_Straight.png|680px]]
| style="padding-bottom: 20px;" | The short 14m median segment in the above examples above satisfies condition #2 for U-turn prevention.
{{mbox|type=protection|text=Be sure the [[Editing_permissions#Locked_junction|junctions are not locked]] above your rank. Otherwise, otherwise drawing a new temporary segment connected to locked junctions may produce a save error even if it is deleted prior to saving.
# Disable the [[Map_Editor_Interface_and_Controls#Settings_Tab|WME setting]] "Draw new roads with all turns allowed" before drawing the new segment.
# Draw the new segment disconnected from any other segment, then drag the end nodes to connect to the junctions.
|workaround options if when any of the segments connected to either junction node are locked above your rankcannot be edited.
<includeonly>Please see the [[Routing penalties/Controlling U-turnsturn penalties#Additional examples|Controlling U-turnsturn penalties]] article for more advanced details, and additional examples.</includeonly><noinclude> 
==== {{@|Additional examples}} ====
<div style="font-size:smaller">
| [[File:U-turn_example_2mediansegs-bdp.png|243px]]
| Cutting a median segment into two may have unintended consequences
| U-turns are legal at this intersection. Even though U-turn prevention will ''not'' be triggered here, Waze will rarely route a U-turn at this intersection. When the railroad was junctioned with the median segment, it cut a single median into two. The two-segment discontinuity between divided roads of Major Blvd can trigger a lower penalty mechanism designed to discourage detours off the main road (see [[Detour_Prevention_Mechanisms/USA#Big_Detours|Big Detour Prevention]], BDP).
|- style="background-color: #fff;"
| [[File:U-turn_example_2mediansegs-allowed.png|243px]]
| Cutting a median segment into two may have unintended consequences
| U-turns are not legal at this intersection, but Waze may route a U-turn here anyway. Cutting the median breaks condition #1, so U-turn prevention will not trigger. Unlike the railroad example aboveFurthermore, BDP may might not trigger here if all of its criteria are not met.
|- style="background-color: #fff;"
| [[File:U-turn_example_curvedU.png|243px]]
| A median segment longer than {{:Routing penalties/U-turn minimum|greater}} or longer will always allow a U-turn| While condition #3 requires a straight segment for determining parallel in and out segments, condition #2 is the measure of the length of the median segment itself. Be careful when the space between the divided road is small. Ensure the U-turn segment is longer than {{:Routing penalties/U-turn minimum|greater}} or longer by adjusting geometry. A median segment of any shape can trigger a U-turn penalty between parallel roads if it is not long enough.
|- style="background-color: #fff;"
| [[File:U-turn_example_parkinglot.png|243px]]