imported>Kentsmith9 m (Created Redirect) |
imported>PesachZ (Created page with "=== {{@|Median U-turn penalty}} === {{anchor|Avoiding U turns|Avoiding U turns in box and partial box intersections}} {{Mbox|type=forum|text=For the latest discussion on this ...") |
||
Line 1: | Line 1: | ||
# | === {{@|Median U-turn penalty}} === | ||
{{anchor|Avoiding U turns|Avoiding U turns in box and partial box intersections}} | |||
{{Mbox|type=forum|text=For the latest discussion on this section please visit [http://www.waze.com/forum/viewtopic.php?t=108731 the wiki forum thread].}} | |||
{{Mbox|type=important|text=It is possible for this method to fail to prevent U-turns in certain circumstances which are presumed to be unusual. 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]}} | |||
[[File:MinSegLengthUturn2.png|border|390px|right|Segment too short to allow two left turns]] | |||
The Waze routing algorithm assesses a [[Routing penalties#Road_configurations|penalty]] for a double-left turn in [[right-hand traffic]] countries and a double-right in [[left-hand traffic]] countries. | |||
==== {{@|Preventing median U-turns}} ==== | |||
U-turns through a median segment will be [[Routing penalties|penalized]] when all three of the below criteria are met. This allows the prevention of U-turns on divided highways, parallel roads, including box (#), and H style intersections. | |||
# The U-turn we want to forbid is one incoming one-way segment, one median segment, and one outgoing one-way segment. | |||
# There is a median segment of length less than 15 m (49 feet). | |||
# The portion of those two segments closest to the median segment must be [[#Checking for parallel segments|within ±5° of exactly parallel]]. | |||
==== {{@|Allowing median U-turns}} ==== | |||
To allow a U-turn through a median, ensure that any one of the [[#Preventing median U-turns|above criteria]] are broken: | |||
* To allow the median U-turn in both directions, it is simplest to make the median segment longer than 15 meters. ''(Breaking criteria #2)'' | |||
* To allow the U-turn in only one direction, it is simplest to adjust the turn angles in only for the segments of the allowed U-turn so they are wider than the [[#Checking for parallel segments|±5° allowance of exactly parallel]]. This is easily achieved without affecting the overall look of the map using a [[Glossary#mDL|Micro-dogleg]]. | |||
==== {{@|Checking for parallel segments}} ==== | |||
A convenient way to check if the two side segments are parallel is to use another segment a reference tool. If the median segment has no geometry nodes, it can be the reference segment. Otherwise you can draw a new segment as a reference tool with no geometry which connects the A and B nodes of the median segment. ''The reference segment can be deleted after the check is complete, if appropriate.'' | |||
Check two angles: | |||
# X — the angle between the incoming one-way segment and the reference segment | |||
# Y — the angle between the outgoing one-way segment and the reference segment. | |||
If the sum of these two angles is within 5° of 180° (between 175-185°), then the roads are considered parallel. | |||
In the example below, angle X is 102°, and angle Y is 75°. The sum is 177°, which is within 3° of 180°. Therefore these roads are considered parallel. | |||
[[File:LilyPondU-turn.jpeg]] |
Revision as of 22:24, 11 August 2015
Median U-turn penalty
For the latest discussion on this section please visit the wiki forum thread. |
It is possible for this method to fail to prevent U-turns in certain circumstances which are presumed to be unusual. If you observe this method to fail when it is implemented properly, please report it in this forum thread |
The Waze routing algorithm assesses a penalty for a double-left turn in right-hand traffic countries and a double-right in left-hand traffic countries.
Preventing median U-turns
U-turns through a median segment will be penalized when all three of the below criteria are met. This allows the prevention of U-turns on divided highways, parallel roads, including box (#), and H style intersections.
- The U-turn we want to forbid is one incoming one-way segment, one median segment, and one outgoing one-way segment.
- There is a median segment of length less than 15 m (49 feet).
- The portion of those two segments closest to the median segment must be within ±5° of exactly parallel.
Allowing median U-turns
To allow a U-turn through a median, ensure that any one of the above criteria are broken:
- To allow the median U-turn in both directions, it is simplest to make the median segment longer than 15 meters. (Breaking criteria #2)
- To allow the U-turn in only one direction, it is simplest to adjust the turn angles in only for the segments of the allowed U-turn so they are wider than the ±5° allowance of exactly parallel. This is easily achieved without affecting the overall look of the map using a Micro-dogleg.
Checking for parallel segments
A convenient way to check if the two side segments are parallel is to use another segment a reference tool. If the median segment has no geometry nodes, it can be the reference segment. Otherwise you can draw a new segment as a reference tool with no geometry which connects the A and B nodes of the median segment. The reference segment can be deleted after the check is complete, if appropriate.
Check two angles:
- X — the angle between the incoming one-way segment and the reference segment
- Y — the angle between the outgoing one-way segment and the reference segment.
If the sum of these two angles is within 5° of 180° (between 175-185°), then the roads are considered parallel.
In the example below, angle X is 102°, and angle Y is 75°. The sum is 177°, which is within 3° of 180°. Therefore these roads are considered parallel.