Junction Style Guide/Controlling turn instructions: Difference between revisions View history

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Before going further, make sure to understand the mechanics of [[Map_Editing_Quick-start_Guide#Turn_restrictions_.28allowed_turns.29|turn restrictions]] in the [[Waze Map Editor]]. If turns are not correctly enabled or restricted, the proper navigation instructions will never be produced for the client app.
Before going further, make sure to understand the mechanics of [[Map_Editing_Quick-start_Guide#Turn_restrictions_.28allowed_turns.29|turn restrictions]] in the [[Waze Map Editor]]. If turns are not correctly enabled or restricted, the proper navigation instructions will never be produced for the client app.


This article covers a summary of how navigation instructions are set by controlling the angle of the junctions. This is briefly covered in the [[Junction_Style_Guide/Diverging_roads|Diverging roads]] article noted above and much more detailed mechanics behind this function can be found in the article [[How_Waze_determines_turn_/_keep_/_exit_maneuvers|How Waze determines turn / keep / exit maneuvers]].
This article covers a summary of how navigation instructions are set by controlling the angle of the junctions. This is briefly covered in the [[Junction_Style_Guide/Diverging_roads|Diverging roads]] article noted above. Much more detailed mechanics behind this function can be found in the article [[How_Waze_determines_turn_/_keep_/_exit_maneuvers|How Waze determines turn / keep / exit maneuvers]].


=== Geometry ===
=== Geometry ===
All junctions should be laid out to follow a few basic forms to ensure better prediction of navigation behavior.
All junctions should be laid out to follow a few basic forms to ensure better prediction of navigation behavior. The table provides guidance for how to set the angles of junctions between segments to achieve the desired navigation instruction listed.
* Departure angle =
* Range =
* Road Type =
* Traffic Side =
* Navigation Instruction =


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* Departure Angle = The deviation from straight ahead (0) in degrees.
* Range = The range of angles that will result in that condition.
* Road Type = The road type connected to the junction. Higher road types take precedence.
* Traffic Side = Left-hand Traffic, Right-hand Traffic, or both
* Navigation Instruction = The instruction to be given through the client app.


* Approximately '''90''' degree departure angle = '''Turn''' instruction
Stay away from the ends of the ranges (22 and 45) as those are tipping points between the settings that are hard to determine visually on the map. Instead stick with the centerpoints (0, 33, 90+) shown in the departure angles column for better predictability.
* Between '''20 and 30''' degree departure angle:
** when only Primary Street and below are involved = '''Keep Right / Keep Left''' instruction
** when Ramps and/or Minor Highway and above are involved = '''Exit Right / Keep Left''' instruction for right-hand drive countries, '''Keep Right / Exit Left''' instruction for left-hand drive countries
* Approximately '''0''' degree departure angle = '''no navigation instruction'''


'''NOTE:''' There are exceptions to these rules since geometry is not the only factor which determines instructions.  See later sections for how [[#Segment_Naming_and_Type|Segment Naming and Type]] can impact instructions.
'''NOTE:''' There are exceptions to these rules covered in the section [[#Segment_naming_and_type|Segment name and type]] below.


These angles allow us to clearly depict the desired result (turn vs. keep) while staying away from the angles that cause uncertain decisions from the routing  algorithms. For example, since 45 degrees is a tipping point for the algorithms, a 44.5 degree angle will behave very differently than a 45.5 degree angle, although they will look identical to the eye.
==== Examples ====
{| class="Wikitable floatright"
| [[Image:Jct_at_grade_keep.png|border]]
|}
For [[Junction_Style_Guide/Revision#Y_Intersections|road splits at a Y]] or [[at-grade connectors]], it is important to identify which road is "straight" and which bears off to the side. It is not good to have one at zero degrees and the other branch at 5 degrees. Instead show the branch at 30 degrees to be sure the Keep Right (or Left) instruction is given. For this case, adjust the [[geometry node]] of the branching road near the junction to control that angle.


Similarly, if we have a [[#Y_Intersections|road split at a Y]] and we want to be clear about which is "straight" and which bears off to the side, having one branch at zero degrees and the other branch at 5 degrees isn't clear and obvious; but "straight" would be much more apparent if the angles were zero degrees vs. 20 degrees.  Since most of us will not have a protractor handy when we are editing, it is best to simply avoid situations where exactness matters.
{| class="Wikitable floatright"
 
| [[Image:Jct_at_grade_turn.png|border]]
This knowledge allows us to control how a junction behaves by modifying a single geometry node in most cases.  This is often useful for [[at-grade connectors]] where sometimes we prefer a "Keep right/left" and other times a "Turn right/left" would be more appropriate.
|}
 
In these two examples of [[at-grade connectors]], if the departure angle is set for 30 degrees, a "Keep Right" instruction is provided to follow the curved one-way connector. But if a "Turn Right" instruction is desired, simply move the geometry node near the junction of the curved connector segment to set the angle closer to 90 degrees.
If we keep the departure angle in the 20 to 30 degree range, we would get a "Keep Right" to follow the curved one-way connector:
{{clear}}
 
: [[Image:Jct_at_grade_keep.png]]
 
But if we move one geometry node to create a 90 degree angle, we would receive a "Turn Right" instruction.
 
: [[Image:Jct_at_grade_turn.png]]
 
Similar rules apply for the end of that segment as well.  If we have a 20 to 30 degree angle as pictured above, there will be no turn instruction, as traffic just smoothly slides into the cross street.  But if we make the end of the segment close to a 90 degree angle, then there would be a turn right instruction for the driver.
 
Furthermore, if the North-South road in that last example were a Minor Highway or a Major Highway, the 20 to 30 degree angle at the start of the connector would produce an "Exit" instruction which may be more confusing than a "Keep" instruction would have been.  So unless this connector is signed with an actual exit sign, a 90 degree start to the connector to produce a "Turn" instruction is most likely preferred.


=== Segment Naming and Type ===
=== Segment name and type ===


The names and road types of the attached segments affect the routing algorithms, in addition to the geometry of the road segments,
The names and road types of the attached segments affect the routing algorithms, in addition to the geometry of the road segments,

Revision as of 06:05, 23 March 2014

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Keep Right Keep Left
Turn Right Turn Left
Exit Right Exit Left

Before going further, make sure to understand the mechanics of turn restrictions in the Waze Map Editor. If turns are not correctly enabled or restricted, the proper navigation instructions will never be produced for the client app.

This article covers a summary of how navigation instructions are set by controlling the angle of the junctions. This is briefly covered in the Diverging roads article noted above. Much more detailed mechanics behind this function can be found in the article How Waze determines turn / keep / exit maneuvers.

Geometry

All junctions should be laid out to follow a few basic forms to ensure better prediction of navigation behavior. The table provides guidance for how to set the angles of junctions between segments to achieve the desired navigation instruction listed.

Departure Angle Range Road Type Traffic Side Navigation Instruction
0 0-21 All All None
33 22-44 All except Ramps, Highways, Freeways All Keep Left and Keep Right
Ramps, Highways, Freeways LHT Exit Left and Keep Right
RHT Keep Left and Exit Right
90 45 - 150 All All Turn Left and Turn Right
  • Departure Angle = The deviation from straight ahead (0) in degrees.
  • Range = The range of angles that will result in that condition.
  • Road Type = The road type connected to the junction. Higher road types take precedence.
  • Traffic Side = Left-hand Traffic, Right-hand Traffic, or both
  • Navigation Instruction = The instruction to be given through the client app.

Stay away from the ends of the ranges (22 and 45) as those are tipping points between the settings that are hard to determine visually on the map. Instead stick with the centerpoints (0, 33, 90+) shown in the departure angles column for better predictability.

NOTE: There are exceptions to these rules covered in the section Segment name and type below.

Examples

For road splits at a Y or at-grade connectors, it is important to identify which road is "straight" and which bears off to the side. It is not good to have one at zero degrees and the other branch at 5 degrees. Instead show the branch at 30 degrees to be sure the Keep Right (or Left) instruction is given. For this case, adjust the geometry node of the branching road near the junction to control that angle.

In these two examples of at-grade connectors, if the departure angle is set for 30 degrees, a "Keep Right" instruction is provided to follow the curved one-way connector. But if a "Turn Right" instruction is desired, simply move the geometry node near the junction of the curved connector segment to set the angle closer to 90 degrees.

Segment name and type

The names and road types of the attached segments affect the routing algorithms, in addition to the geometry of the road segments,

A rule of thumb is if you want a turn to be announced, having a name difference between segments will improve the chances (but not guarantee) that it will happen. In the case of the at-grade connector example above, the connector should either have a different name than the road it is leaving, or no name at all. (See At-grade connectors#Road name.)

Road type is a factor in determining navigation instructions as well, but names and angles are much more important. If you have multiple roads meeting at a junction and two of those road segments line up at close to zero degrees and they have the same name, that will be considered straight no matter what road types are used. An example demonstrating this is shown in the discussion on Y-intersections in a later section.

Road type will be the determining factor when all names are different. For example imagine you have a Ramp segment leading to a Freeway segment and another Ramp segment. The Ramp segment will be considered the "straight" continuation and there will be no announcement while a navigation instruction will be given to proceed to the Freeway segment. This is true even if the initial Ramp and the Freeway align at close to 0 degrees and the second Ramp departs at a 20 to 30 degree angle.


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