Difference between revisions of "Routing penalties/Controlling U-turn penalties"

From Wazeopedia
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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 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]}}
 
{{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]}}
 
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[[File:U-turn_Roads.png||350px|right]]
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[[File:U-turn_Roads.png||300px|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 box- (#) and H-style intersections on divided highways and parallel roads.
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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 box- (#) and H-style intersections on divided and parallel roads.
  
  
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* To allow median U-turns in both directions, break condition #2 by making the median segment longer than 15 m (49.21 ft)
 
* 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 adjust the angle without affecting appearance)
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* 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)
  
 
==== {{@|Checking for parallel incoming and outgoing segments}} ====
 
==== {{@|Checking for parallel incoming and outgoing segments}} ====

Revision as of 20:41, 24 August 2015

Median U-turn penalty link to this section

For the latest discussion on this section please visit the wiki forum thread.
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 this forum thread


U-turn Roads.png

The Waze routing algorithm assesses a penalty for a double left or right turn, which can be used to prevent U-turns at box- (#) and H-style intersections on divided and parallel roads.


Preventing median U-turns link to this section

A large U-turn penalty is applied for a double left/right turn when all three of the conditions below are met:

  1. The U-turn is composed of an incoming segment, a single median segment, and an outgoing segment
  2. The length of the median segment is shorter than 15 m (49.21 feet)
  3. The incoming and outgoing segments are within ±5° of parallel to each other

Allowing median U-turns link to this section

To allow a double left/right turn through a median segment, break any one of the 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 non-parallel. (Tip: consider using a Micro-dogleg to discreetly tweak the angle without affecting appearance)

Checking for parallel incoming and outgoing segments link to this section

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 Junction Angle Info script add-on, which can be set to report absolute angles or turn angles ("departure"). For the purpose of determining parallelism, summing either measurements will work.

U-turn Parallel Check Straight.png


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.

U-turn Parallel Check Curved.png