# Changes

## Routing penalties/Controlling U-turn penalties

, 6 months ago
Fixed JB rank error (was 5, now using Rank template) in "Allowing median U-turns" section
=== {{@|Median U-turn penalty}} ===
{{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=http://www.waze.com/forum/viewtopic.php?t=108731 |<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]]|- | 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 forum threadand with local experts to learn the correct road type to use for '''median segments''' in your area.|}The Waze routing algorithm has a method of [[Routing penalties#Road_configurations|penalizing]]some double-left 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.}}
[[File:U-turn_Roads.png||360px|right]]
The Waze routing algorithm assesses a [[Routing penalties#Road_configurations|penalty]] for a double left or right turn, which can be used to prevent U-turns at H-style intersections on divided and parallel roads.
==== {{@|Preventing median U-turns}} ====
A An extremely large U-turn penalty is applied set for a double -left/or double-right turn when '''''all three''''' of the conditions below are met:
# '''Three segments''': The U-turn involves is a reversal of driving direction through 3 three segments: <br>an incoming segment&nbsp;(A), a single median segment, &nbsp;(B) and an outgoing segment&nbsp;(C).# '''Short median''': The length of the median segment &nbsp;(B) is shorter than 15 m (49equal to {{:Routing_penalties/U-turn_minimum|less}} or less.21 feet)# '''In/out parallelism''': The incoming in and outgoing out segments (A&nbsp;and&nbsp;C) are [[#Checking for parallel incoming and outgoing segments|within ±5° of parallel]] to each other.
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{{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 [http://www.waze.com/forum/viewtopic.php?p=994385#p994385 this forum thread]}}
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==== {{@|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/right U-turn from only one direction, first setup the intersection to allow U-turns in both directions. Then, add a [[Junction Box]], and restrict the prohibited U-turn through route. A rank {{Rank|jb}} user or above is required to install a median segmentJunction Box. {{mbox|text=Previously, break any one unidirectional U-turn prohibition on a divided road was set up by breaking condition #3 of the U-turn prevention mechanism through the use of a [[Glossary#mDL|micro-dogleg]]. {{As of|2017}}, Waze staff has expressed a preference that map editors use Junction Boxes in these situations.}}<!-- OLD INFORMATION * To allow a U-turn from only one direction, first set up U-turn prevention for both directions. Break condition #Preventing median 3 on the side where U-turnsare allowed. Increase or decrease the angles so that the in and out segments (A and C) are [[#Checking for parallel incoming and outgoing segments|above criterianot 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]]--><br>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 ==== {{@|Checking for both directions. For the side where U-turns are allowed, make the parallel 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)}} ====
Condition #3 for U-turn prevention requires that the in and out segments (A&nbsp;and&nbsp;C) are within ±5º of parallel to each other. This is checked by using a ''straight'' median segment as the reference and the [[Scripts#WME_Junction_Angle_info|Junction Angle Info]] (JAI) browser extension to measure angles. JAI may be set for absolute or [[Interactive_junction_instruction_algorithm#Turn_angle|turn angles]]; using either is OK.
===== {{@|Checking for parallel Straight median segments}} =====If the median segment is straight, sum the two angles making up the U-turn::# The angle between the incoming and median segments (between A and B):# The angle between the median and outgoing segments(between B and C)The in and out segments (A&nbsp;and&nbsp;C) are considered parallel if the sum is {{font color|red|between 175º and 185º}} . <br>{| 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 satisfies condition #2 for U-turn prevention.|}
Condition #3 for U-turn prevention requires ===== {{@|Curved median segments}} =====If the incoming median segment&nbsp;(B) has been shaped with geometry nodes, it is not straight and outgoing segments to cannot be within ±5º of parallel to each otherused for determining parallelism. These two segments are considered parallel if their angles with respect to Instead, draw a ''straight'' segment connected at the same in and out junctions (where in-segment&nbsp;(A) junctions with the median segment&nbsp;(B) and where the median segment sum to 180±5º &nbsp;(B) junctions with the out-segment&nbsp;(iC)).eCheck the angles using this new straight segment, between 175º and 185º)delete the new segment afterwards. <br>Angles can be easily checked with the [[Scripts#WME_Junction_Angle_infoFile:U-turn_Parallel_Check_Curved.png|Junction Angle Info]] script add-on, which can be set to report absolute angles or [[How_Waze_determines_turn_/_keep_/_exit_maneuvers|turn angles680px]] ("departure"). For the purpose of determining parallelism, summing either measurements will work.
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{{mbox|type=protection|text=Be sure the [[File:U-turn_Parallel_Check_StraightEditing_permissions#Locked_junction|junctions are not locked]] above your rank.pngOtherwise, drawing a new temporary segment connected to locked junctions may produce a save error even if it is deleted prior to saving.{{Expand|# Disable the [[Map_Editor_Interface_and_Controls#Settings_Tab|centerWME 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 when any segments connected to either junction node cannot be edited.|nt=yes}}}}
<includeonly>Please see the [[Routing penalties/Controlling U-turn penalties#Additional examples|Controlling U-turn penalties]] article for more advanced details, and additional examples.</includeonly><noinclude>
However==== {{@|Additional examples}} ====<div style="font-size:smaller">{| class="wikitable" cellpadding=2 style="width: 100%; text-align: left;" ! style="width: 247px" | Example! style="width: 120px" | Tip! Details|- style="background-color: #fff;"| [[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, if Waze will rarely route a U-turn at this intersection. When the railroad was junctioned with the median segment has geometry nodes and is not straight, it cannot be used as cut a single median into two. The two-segment discontinuity between divided roads of Major Blvd can trigger a referencelower penalty mechanism designed to discourage detours off the main road (see [[Detour_Prevention_Mechanisms#Big_Detours|Big Detour Prevention]], BDP). |- style="background-color: #fff;"| [[File:U-turn_example_2mediansegs-allowed. In png|243px]]| Cutting a median segment into two may have unintended consequences| U-turns are not legal at this caseintersection, temporarily add but Waze may route a U-turn here anyway. Cutting the median breaks condition #1, so U-turn prevention will not trigger. Furthermore, BDP 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 {{:Routing penalties/U-turn minimum|greater}} or longer will always allow a U-turn| While condition #3 requires a straight segment to for determining parallel in and out segments, condition #2 is the measure of the same junctions as length of the existing curved mediansegment itself. Be careful when the space between the divided road is small. Check Ensure the angles using this straight U-turn segment is {{:Routing penalties/U-turn minimum|greater}} or longer by adjusting geometry. A median and delete when donesegment of any shape can trigger a U-turn penalty between parallel roads if it is not long enough.<br>|- style="background-color: #fff;"| [[File:U-turn_Parallel_Check_Curvedturn_example_parkinglot.png|243px]]| To ensure proper routing between two closely spaced parallel roads, connect the two with a segment {{:Routing penalties/U-turn minimum|greater}} or longer| U-turn prevention triggers for both double-left and double-right turns over any road type. If the three conditions for median U-turn prevention are met, a large penalty will be applied, irrespective of whether the turn is onto the same road in the opposite direction or onto a completely different road. Both double-left and double-right turns can be penalized, regardless of country, and can occur for one way or two way segments.|}</div></noinclude>
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