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Fixed JB rank error (was 5, now using Rank template) in "Allowing median U-turns" section
{{anchor|Avoiding U turns|Avoiding U turns in box and partial box intersections}}
{{hatnote|This article discusses double-turn U-turns. For standard one or two segment U-turns, adjust the [[Interface_guide#Junction_Arrows|junction arrows]].}}
{{MboxForumLink|type=forum|style = background: #cadceb;|text=For the latest discussion on this section please visit the wiki forum thread [ |<nowiki>[Page Update] Intersections / U-turns under 15m</nowiki>].|section=yes}}
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# '''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. [[File:U-turn selective Uturn prevention.png|center]]-->
<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}} ====
| [[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).
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| [[File:U-turn_example_2mediansegs-allowed.png|243px]]