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.

Introduction

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.

Definitions

• 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  Freeway ,  Major Highway , or  Minor Highway , will be referred to in this page as a highway.
• 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.
  To explain;
  • 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

Roundabouts
Normal	Non-Normal
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.

Directions

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 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). The order of preference for Best Continuation is; Primary name + Type match Alt name + Type match Primary name match, OR Primary name <=> Alt name Cross-match Alt name match Type match City names have no affect on matches. 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. In order for a Cross match to work there must be at least one alt name on both involved segments (even though they don't necessarily match each other). It will work even if the are no Primary names on those segments. It will not work if all three segments at a split have a matching Primary name or a matching Alternate name. An Alt match is when two adjacent segments have an identical alternate name (regardless of city name). It will not work if all three segments at a split have a matching Primary name. It will work even the OUT segment (the one leaving the split) has no Primary name. Bring up comments or questions on this page in this forum . ~PesachZ (PM [Help])

The interactive algorithm

(01)

Other than the origin and the destination, are there any other segments connected to this junction?

YES

NO => No Instruction

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(19)

Do the origin and the destination meet at a Roundabout?

YES

NO

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(02)

Is the turn angle from the origin to the destination between 45.14° and 150°?

YES

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.

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(03)

Which direction is the turn?

Left => Turn Left

Right => Turn Right

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(04)

Are there any other branches with unrestricted turns from the origin?

YES

NO => No Instruction

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(13)

Is there more than one (1) other branch?

YES

NO

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(14)

Are the two branches (the destination and the other branch) overlapping?

YES => No Instruction

NO

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(05)

Is the name of the origin and the destination identical?

YES

NO

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(06)

Are the origin and the destination the same road type?

YES

NO

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(07)

Are both the name AND the road type of any of the other branches identical to the origin?

YES

NO => No Instruction

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(08)

Is there any other branch to the left of the destination branch?

YES

NO

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(20)

Is this an overlapping segment, is it overlapped by any other branch?

YES

NO

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(25)

Are the segments in a right hand traffic country (such as the USA)?

YES

NO => Keep/Stay Right

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(21)

Is the origin a highway? ( Freeway ,  Major Highway , or  Minor Highway )

YES

NO

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(22)

Is the destination a highway? ( Freeway ,  Major Highway , or  Minor Highway )

YES => Keep/Stay Left

NO => Exit Left

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(23)

Is the origin a  Ramp ?

YES

NO => Keep/Stay Left

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(24)

Is the destination a highway ( Freeway ,  Major Highway , or  Minor Highway ), or a  Ramp ?

YES => Keep/Stay Left

NO => Exit Left

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(09)

Is the name of any of the other branches identical to the origin?

YES

NO => No Instruction

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(10)

Are the origin and the destination the same road type?

YES

NO

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(11)

Is the name of any of the other branches identical to the origin?

YES

NO

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(12)

Is the road type of any of the other branches identical to the origin?

YES

NO => No Instruction

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(26)

Are the segments in a left hand traffic country (like the UK)?

YES

NO => Keep/Stay Left

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(15)

Is the origin a highway? ( Freeway ,  Major Highway , or  Minor Highway )

YES

NO

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(16)

Is the destination a highway? ( Freeway ,  Major Highway , or  Minor Highway )

YES => Keep/Stay Right

NO => Exit Right

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(17)

Is the origin a  Ramp ?

YES

NO => Keep/Stay Right

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(18)

Is the destination a highway ( Freeway ,  Major Highway , or  Minor Highway ), or a  Ramp ?

YES => Keep/Stay Right

NO => Exit Right

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(27)

Are there five (5) or more segments (junctions) connected to the roundabout?

YES => At the Roundabout Take the #xx Exit

NO

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(28)

From the perspective of the origin, are the roundabout angles to all the other segments between 0°-15°, or 75°-105°?

YES

NO => At the Roundabout Take the #xx Exit

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(29)

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

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The navigation instructions

No Instruction

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)

Displayed Icons
Livemap & WME	Client App
	Not Available in Client App

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Turn Right

Displayed Icons
Livemap & WME	Client App

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Keep/Stay Right

Displayed Icons
Livemap & WME	Client App

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Exit Right

Displayed Icons
Livemap & WME	Client App

NOTE:

• In a left hand traffic country this instruction does not exist, and will instead give a Keep/Stay_Right instruction.
• You will only get an Exit instruction on a turn angle less than 45.04°, because it is assumed no true exit would have a turn sharper than 45.04°.

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Turn Left

Displayed Icons
Livemap & WME	Client App

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Keep/Stay Left

Displayed Icons
Livemap & WME	Client App

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Exit Left

Displayed Icons
Livemap & WME	Client App

NOTE:

• In a right hand traffic country this instruction does not exist, and will instead give a Keep/Stay_Left instruction.
• You will only get an Exit instruction on a turn angle less than 45.04°, because it is assumed no true exit would have a turn sharper than 45.04°.

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At the Roundabout Take the #xx Exit

The "#xx" will be 1st, 2nd, 3rd, etc.. The counting starts from the origin.

Displayed Icons
Livemap & WME	Client App

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.

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At the Roundabout Turn Left

Displayed Icons
Livemap & WME	Client App

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At the Roundabout Turn Right

Displayed Icons
Livemap & WME	Client App

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At the Roundabout Continue Straight

Displayed Icons
Livemap & WME	Client App

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At the Roundabout Make a U-Turn

Displayed Icons
Livemap & WME	Client App

NOTE: Currently this is only displayed in the client, but there is no verbal instruction (due to a bug).

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