User:Kjg53/Interactive junction instruction algorithm
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This is a clickable interactive guide to determine what instruction, if any, will be given at the junction between any 2 segments.
A text version of this information is available here.
There will eventually be encyclopedia style illustrations for all the various configurations to visually describe the setup.
- 1 Introduction
- 2 Definitions
- 3 Directions
- 4 The interactive algorithm
- 5 The navigation instructions
Understanding how and which instructions are provided requires first understanding a few concepts.
- This page is discussing the instruction which will be provided by the Waze server (or not provided) when traveling from one segment, through a junction, and onto a second segment.
- How Best Continuations work. Any time the destination segment is the Best Continuation there will not be an instruction provided.
While the illustrations displayed by each question may not represent every possible variation, they do represent the difference between the two options in that question. Please choose the most appropriate answer.
- ORIGIN: The segment you are on before going through the junction, in other words the segment you are coming from will be referred to as the origin, and corresponds to s-in in the the algorithm text provided by Waze staff.
- In terms of navigation, the segment you are being routed from is the origin.
- DESTINATION: The segment you will be on after the junction, in other words the segment you are going to will be referred to as the destination, and corresponds to s-out in the the algorithm text provided by Waze staff.
- In terms of navigation, the segment you are being routed on to is the destination.
- BRANCH: Any segments other than the destination which leave the junction at an angle less than 45.04° will be referred to as other branches, and corresponds to s-N, or s-1,2,3,4... in the the algorithm text provided by Waze staff.
- OVERLAPPING: When the beginning portion two segments are directly on top of each other, meaning they both leave the junction at the exact same angle as each other, they will be referred to as an overlapping segment.
- HIGHWAY: Any road typed in Waze as a highway. , , or , will be referred to in this page as a
- TURN ANGLE: The turn angle is the angle from the origin to the destination. A perfectly straight road with a junction in the middle would have a turn angle of 0°. The angle then gets wider as you turn to either side. A perfect left or right turn would be 90°. A U-turn at a junction between two segments would represent a 180° turn.
Turn Angles Standard Turn Angle 37° Angle 90° Dogleg Geometry Node
- NO-NAME Segments: A segment with no name (the "none" check-box for street name is checked) is considered to have "no-name" as a name for the Best Continuation algorithm. So two segments with no name, will be considered to have identical names, even if they would inherit different names for TTS.
- ROUNDABOUT ANGLE: The Roundabout angle is the angle of any segment connected to the roundabout from the perspective of the origin. The actual turn angle of the segments is irrelevant.
- Draw an imaginary line straight through the roundabout to the other side of the roundabout from junction node where the origin joins the roundabout. This will represent a 0° Roundabout angle, any deviation to the right or left will increase the angle.
- Draw another imaginary line across the roundabout exactly perpendicular to the first imaginary line. This will represent a 90° Roundabout angle to either side.
- For more info see the roundabouts page
|All other segments are within the allowed ±15° from either 0° or 90°.||Not all other segments are within the allowed ±15° from either 0° or 90°.|
|The allowed range for roundabouts may actually be less than ±15°, this is currently being tested.|
To use this interactive flowchart;
- Start with the first question in The Interactive Algorithm.
- Click on the appropriate answer which best matches your situation. A new question will jump to the top of the screen
- Continue answering the questions until an instruction is displayed at the top of the screen.
- This is the instruction that the Waze server should give when transversing this junction between the two segments you described as the origin and the destination.
| As of September 2014[update] This algorithm was changed to also factor in alternate names. This algorithm is still correct when none of the segments have alternate names. If there are alternate names on any of the segments there are a few modifications (in bold).
A Cross-match is when the primary name of one segment is identical to the alternate name of an adjacent segment. It had the same priory as a Primary name match.
An Alt match is when two adjacent segments have an identical alternate name (regardless of city name).
The interactive algorithm
Other than the origin and the destination, are there any other segments connected to this junction?
|NO => No Instruction|
Is the turn angle from the origin to the destination between 45.14° and 150°?
|NO, the turn angle is less 45.04°|
|NO, the turn angle is greater than 150°|
|SPECULATION NOTE: This is unconfirmed Turns with angles greater than 150° will follow the same instruction path as 45.14°-150°, but the Waze routing server will penalize this turn, and avoid routing through it.|
Are the two branches (the destination and the other branch) overlapping?
|YES => No Instruction|
Are both the name AND the road type of any of the other branches identical to the origin?
|NO => No Instruction|
Is the road type of any of the other branches identical to the origin?
|NO => No Instruction|
Are there five (5) or more segments (junctions) connected to the roundabout?
|YES => At the Roundabout Take the #xx Exit|
From the perspective of the origin, are the roundabout angles to all the other segments between 0°-15°, or 75°-105°?
|NO => At the Roundabout Take the #xx Exit|
What direction is the destination relative to the origin?
|Left => At the Roundabout Turn Left|
|Straight => At the Roundabout Continue Straight|
|Right => At the Roundabout Turn Right|
|U Turn, Back => At the Roundabout Make a U Turn|
There will be No instruction given passing through this junction. This can be caused by several factors including
- Best Continuation
- Certain cases with an overlapping segment
- The instruction would be Continue Straight (this doesn't yet exist in the client application)
At the Roundabout Take the #xx Exit
The "#xx" will be 1st, 2nd, 3rd, etc.. The counting starts from the origin.
NOTE: In the client app there will be a digit inside the circle representing which number exit you must take (starting from the origin).
- If the roundabout is not formed correctly (more than one entering/exiting segment connected to same roundabout node), you may get an instruction "at the roundabout, exit number 0" with a partial verbal instruction.
At the Roundabout Make a U-Turn
NOTE: Currently this is only displayed in the client, but there is no verbal instruction (due to a bug).
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