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

From Wazeopedia
({{@|Preventing median U-turns}}: simplification. set instead of assess or apply (consistently). Use of segments "A" "B" and "C" instead of "incoming" "median" and "outgoing")
({{@|Allowing median U-turns}}: consistent use of "conditions" instead of switching to "criteria", segments A,B,C, Use simpler words.)
Line 18: Line 18:
 
==== {{@|Allowing median U-turns}} ====
 
==== {{@|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 criteria]]. For example:
+
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 median segment longer than 15 m (49.21 ft)
+
* 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 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)
+
* 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>
 
<br>
  

Revision as of 11:59, 9 September 2015

Median U-turn penalty link to this section

For the latest discussion on this section please visit the wiki forum thread.
U-turn Roads.png

The Waze routing algorithm sets a 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 link to this section

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

  1. The U-turn involves a reversal of driving direction through 3 segments:
    A) an incoming segment, B) a single median segment, and C) an outgoing segment
  2. Segment B is shorter than 15 m (49.21 feet)
  3. Segment A and segment B are within ±5° of parallel to each other


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


Allowing median U-turns link to this section

To allow a double-left or double-right turn through a median segment, break any one of the 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 not parallel. A micro-dogleg can be used to change the angle without changing the appearance of segment.


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

Common mistakes link to this section