User:Kjg53/Interactive junction instruction algorithm View history

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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.