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When traffic moves between two roads that are at the same [[Glossary#Grade|grade]], these connecting segments are not technically [[Road types/USA#Ramps|ramps]] to Waze (unless it falls into one of the [[#Exceptions|Exceptions]] listed below). How to handle these connectors depends on the exact situation.
When traffic moves between two roads that are at the same [[Glossary#Grade|grade]], these connecting segments are not technically [[Road types/USA#Ramps|ramps]] to Waze (with some [[At-Grade_Connectors#Exceptions|exceptions]]). Rather, they are considered '''at-grade connectors''' (AGCs).  When and how to implement an AGC in Waze depends on circumstances.


== Applications ==
{{Red|This article suggests additional clarity to the Waze wiki regarding [[At-Grade_Connectors|At-grade connectors]], focusing on when they are and are not called for.  It is a personal work for local purposes and is not offered nor reviewed as a contribution to the US or Global Waze wiki.}}


As commonly applied in Waze, at-grade connectors serve the following purposes in decreasing order of priority:
==  Applications ==


* '''Represent a physically separate, distinct road corridor''' that connects two larger roads at the same elevation.  To qualify for this purpose, a connector must be sufficiently isolated from the larger roads that a typical driver would be surprised not to see it explicitly depicted on the client display.  This is At-Grade Connectors' primary function and they are always called for in this situation.
The rule for AGCs is "when in doubt, leave it out."  For most intersections, separately mapped turn lanes confer no benefit. They add to the complexity of the display and substantially increase the effort required to verify connectivity, turn restrictions, directionality, name, etc.  AGCs can also confuse routing for drivers who request a route while waiting at a stoplight on or near the AGC.  If Waze snaps the driver to the AGC, it will offer a route assuming the driver is committed to the turn, which may not be the case.


* '''Prevent incorrect "snapping" of drivers to nearby roads.'''  Where frontage roads parallel very wide and intersecting highways for an extended distance, At-Grade Connectors at the intersections may discourage Waze from snapping drivers to the frontage roads.  This is an uncommon situation.
Editors sometimes add AGCs because the satellite image suggests a separate turn lane when viewed with high magnification.  This is never a good enough reason to map an AGC.


[[File:AGCs_and_Missing_Roads.jpg|left|thumb|300px|'''Situations that do and don't throw the "missing road" Map Problem.'''  The red bar is 100 meters long.  Despite the presence of short dedicated turn connectors at Pine Canyon and Jolon Rd, the absence of At-Grade Connectors on the Waze map does not trigger a "missing road" Map Problem.  Wazers passing through the gas station, however, do cause this error.  The problem was solved with a Gas Station Area Place rather than with an At-Grade Connector through the gas station.]]
The following applications support use of an AGC.


* '''Prevent "missing road" automated Map Problem errors.'''  Tracks that appear to Waze to be "cutting the corner" may cause Waze's automated missing-road detection algorithms to flag a Map Problem.  Adding At-Grade Connectors to prevent these is usually encouraged but in some cases, such as large bowtie junctions, may result in an excessively cluttered and confused display.
=== Represent a physically separate road corridor ===


* '''Advance timing of spoken turn alerts.'''  At-Grade Connector cause turn alerts to be issued earlier.  In complex situations, such as highways of three or more lanes in one direction and/or uncommonly early "commit points" due to extended road striping or physical barriers for the turn, advancing the alert may help prevent missed turns.  In most cases, however, the default turn timing is adequate; in particular effort should focus on timing of penultimate, not final, turn alerts.  Final turn alerts at complex intersections almost always come too late for drivers who hadn't been paying attention to the previous alerts and the community generally does not modify the maps to accommodate those situations.
Ideally, AGCs represent physically separate, distinct road corridors that connect two larger roads at the same elevation.  The physical corridor must be sufficiently isolated from the roads it connects that typical drivers would expect to see it explicitly depicted on the map, much like a freeway ramp.  [[Update_Requests_in_Waze_Map_Editor|Update Requests]] from users that the map should show a connector warrant this application.


{{Clear}}
=== Prevent incorrect driver locating ===


== Should the connector be mapped? ==
Where frontage roads parallel very wide and intersecting highways for an extended distance, AGCs at the intersections may discourage Waze from snapping drivers to the frontage roads.  This is uncommon.


First and foremost, the need to have the connector mapped needs to be established.  As the driver approaches an intersection, Waze has usually given at least one warning that a turn is imminent, and we can assume that the driver is already looking for turn lanes. For most intersections, that is enough to guide the driver into the proper lane and to turn at the proper time; in other words, it is enough that the two roads intersect without separately mapped turning lanes.
=== Properly route side-road access ===


There are only a few situations in which connectors are called for in an intersection:
Sometimes side roads, especially parking-lot roads, connect near intersections in such a way that the side road can only be accessed from a separated right-turn lane.  Drivers being routed to the side road must first diverge from the main road, while drivers emerging from the side road can only turn right and then continue along the right-turn path.  Such a side road requires joining to an AGC to ensure proper routing.
*When the turn lane physically separates from the main road well in advance of the intersection
*When the turn lane is far enough from the point of intersection on the map (due to the size of the intersection or the angle at which the roads meet) that the driver might overshoot while waiting for a delayed "turn" audible, or that the Waze client might become confused and disrupt navigation
*When the area is "busy" enough that the driver may not get any advance warning that a turn is coming up--in which case a connector lets you notify the driver a little earlier
*When there are user complaints ([[Update_Requests_in_Waze_Map_Editor|Update Requests]]) that the audible was too late, or that the map should have shown a connector


When in doubt, leave it out. Each connector complicates the map and adds to your workload when the time comes to check connectivity, direction, name, etc.
=== Prevent "missing road" errors ===


== {{anchor|How to label the connector type}} Road type ==
[[File:AGCs_and_Missing_Roads.jpg|right|thumb|250px|'''Situations that do and don't throw the "missing road" Map Problem.'''  Before the Parking-Lot Road was added, drivers transiting through the gas station triggered "missing road" Map Problems.  Drivers transiting the main intersection, however, did not.  The connectors at the intersection depart no further than 30 m from the center of the intersection.  The path through the gas station departs from the intersection by at least 65 m.  Therefore, At-Grade Connectors are not required at the main intersection to prevent MPs, but the Parking-Lot Road is.]]


Although sometimes referred to as ramps, to Waze these are '''not''' ramps.  Ramps in Waze should only be used for situations where two roadways have a grade separated intersection or if the situation matches one of the [[#Exceptions|Exceptions]] listed below.
When Waze observes repeated traffic through an area where no road is mapped, it may file a "missing road" Map Problem (MP) at the location.  Driver paths that repeatedly "cut the corner" at an intersection can cause this error, but only when the corner-cutting path strays significantly from the intersection junction node.  For example, the two short dedicated turn connectors physically present at the intersection of Pine Canyon and Jolon Roads (pictured) come no closer than 30 m to the junction node, but have not caused missing-road MPs.  However, a path through the gas station that comes at closest 65 m to the junction node does, necessitating a Parking-Lot Road to prevent MPs (being a corner gas station, it will enjoy improved routing as well).


The connector segment's type should be set based on the '''lowest''' of the types of roads it connects.
Waze has not released the distance threshold for triggering a missing-road MP.  It appears to have changed over time, and it may change again.  {{as of|2015|3}}, even departures on the order of 20 m triggered MPs, resulting in numerous unfounded MPs at large city intersections.  This article assumes that 50 m is a more likely long-term threshold.


*Ex: Street to Minor Highway should be Street type.
Taking 50 m as the missing-road MP threshold, AGCs would then be appropriate to represent corner-cuts that ''come no closer than 50 m to the main intersection junction node''. Corner-cuts that come closer to the junction node than 50 m would not warrant AGCs.
*Ex: Minor Highway to Primary Street should be Primary Street type.
*Ex: Primary Street to Primary Street should be Primary Street type.


Example:
Uncommonly large bowtie junctions involve a tradeoff.  While adding AGCs for the corner paths may prevent missing-road Map Problems, they may also result in an excessively cluttered and confused display.  It is thought better in such cases to omit the AGCs and tolerate the occasional missing-road MP.


[[Image:At-grade_example1.jpg]]
Note that, even if the separation of the turn path from the center of the intersection does not warrant an AGC, an AGC may still be called for to advance the timing of spoken turn alerts as described below.


Also note how the top-left quadrant of the intersection does not have a connector mapped because it does not meet the requirement of being significantly separated from the main intersection.
=== Advance timing of spoken turn alerts ===


== {{anchor|How to name the connector}} Road name ==
By advancing the location of the turn on the Waze map, AGCs advance the timing of turn alerts issued to drivers.  In most cases the default alert timing is adequate, but in complex situations, advancing the alert may help prevent missed turns.  Such situations can include:


In most cases, leaving the segment unnamed will be sufficient.  Navigation instructions will simply use the name of the segment to which the connector segment connects.
* connectors departing from highways of three or more lanes in one direction;
* an uncommonly early turn commitment due to extended road striping or physical barriers;
* limited visibility of the upcoming intersection; or
* Update Requests complaining of inadequate alert timing.


If there are specific signs at the intersection which are confusing or contrary to the destination road segment name, then a name can be applied to the connector.
Note that, even if inspection suggests no advance of the turn alert is necessary, an AGC may still be warranted to prevent "missing road" errors as described above.


== {{anchor|Geometry of the connector}} Geometry ==
==== Assessing the need for advanced alerts at complex intersections ====


The [[Junction Style Guide]] provides significant information on how to best set the geometry of the connector to get the best routing and text-to-speech result. Be sure to review that article when updating or creating these connectors.
When considering an AGC to advance a turn alert at a complex intersection, concern should focus on the penultimate, not the final, voice instruction.  Final turn alerts at complex intersections almost always come too late for drivers who missed the previous alerts, and the editing community generally does not modify the maps to accommodate those situations. However, if the penultimate voice instruction would arrive too late for a driver to reach the correct turn lane, that would warrant an AGC for the purpose of advancing the turn alert.


== {{anchor|Turn restrictions necessary for proper connector routing}} Turn restrictions ==
A simple scoring system using "complexity points" can help assess the need for advanced alerts using AGCs.  Measure the distance between the intersection junction node and the "commit location" where a driver must commit to a dedicated turn lane, and, for every full 75 m of distance involved, add one point.  Then add another point for every lane change, worst-case, that an approaching driver would have to make to be in the correct through lane to depart for the turn; do not include the dedicated turn lane itself.  If the resulting score is three or less, advancing the turn alert is almost certainly unnecessary.  If the score is four or more, it may be appropriate to advance the turn warning with an AGC.  As a rough rule of thumb, the departure junction of the AGC may be moved up by 75 m for every point over three.


Connectors, if simply added to the map and all turns allowed, would cause significant routing challenges, especially between two 2-way roads. Split roadways have their own challenges, but turn restrictions, due to the 1-way nature of the main segments, are simpler.
This scoring system is a guideline only.  The actual necessity for advancing turn alerts can depend on additional factors such as an uncommonly early commit location (more than 225 m from the intersection), a pattern of heavy but high-speed traffic, poor intersection visibility, other nearby turns that the driver might confuse with the desired turn, and as always, user reports of inadequate alert timing.


In the US, a simple right-turn connector between two 2-way streets, requires that the right turn be restricted at both the primary intersection, and at the connector itself so Waze will not be allowed to tell the driver to turn left across the road to get onto the connector.
{{Clear}}
 
[[Image:Atgrade example3.jpg]]
 
 
AND, at the end of the connector, the left turn must be restricted:
 
[[Image:Atgrade example2.jpg]]
 
 
If you enable the "show all restricted connectivity arrows" function in the editor at this intersection, you can see there are many restricted turns. This is sometimes a target for someone looking to remove all restricted turns by abusing the use of the 'w' or '''Allow All''' turns function:
 
[[Image:Atgrade example4.jpg]]
 
== Exceptions ==
{{construction
| contact    = http://www.waze.com/forum/viewtopic.php?f=276&t=86666
| contacttype = forum
| draft      = yes
| open        = no
| revision    = yes
| section    = yes
| talk        = no
}}
 
=== Median U turn intersection (MUTI) ===
 
[[File:MUTI.png|250px|thumbnail|right]]The median crossing segments in a [http://www.fhwa.dot.gov/publications/research/safety/09057/ median U turn (aka "Michigan left") intersection] should be set to the {{Ramp}} type.{{clear}}
 
=== Restricted crossing U turn (RCUT) intersection ===
 
[[File:RCUT.png|250px|thumbnail|right]]The median crossing segments in a [http://www.fhwa.dot.gov/publications/research/safety/09059/ restricted crossing U turn (aka "J turn" or "Superstreet") intersection] should be set to the {{Ramp}} type.{{clear}}
 
=== Displaced left turn (DLT) intersection ===
 
[[File:DLT.png|250px|thumbnail|right]]The crossover left turn lanes and the resultant elongated right turn lanes in a [http://www.fhwa.dot.gov/publications/research/safety/09055/ displaced left turn (or "continuous flow") intersection] should be set to the {{Ramp}} type.{{clear}}
 
=== Jughandle ===
 
[[File:Jughandle.png|250px|thumbnail|right]][http://www.fhwa.dot.gov/publications/research/safety/07032/ Jughandle] segments should be set to the {{Ramp}} type.{{clear}}
 
=== Signed, numbered exit ===
[[File:GSP_10.jpg|right|border]]
'''Example:''' Garden State Parkway Exit 10 in Cape May Court House, New Jersey, USA.  The Garden State Parkway is mostly a freeway class toll-road that runs north/south through New Jersey.  As the Parkway approaches its southern terminus, the number of lanes reduce and exits become a mix of grade separated ramps and at-grade intersections. In order to receive an [[Junction_Style_Guide#Controlling_Turn_Instructions|instruction for Exit Right]] rather than Keep Right or Turn Right, this connector needs to be a ramp.
{{clear}}
 
{|style="margin: 0 auto;"
|- valign="top"
| [[File:GSP_10A.jpg|x162px]]
| [[File:GSP_10B.jpg|x162px]]
| Going north, the right turn lane is signed as Exit 10B and the left turn lane is signed as Exit 10A (and reversed going south).
|}
 
 
[[Category:Style Guides]]
[[Category:Waze Map Editor]]
[[Category:Update what links here]]

Latest revision as of 15:55, 15 August 2015

When traffic moves between two roads that are at the same grade, these connecting segments are not technically ramps to Waze (with some exceptions). Rather, they are considered at-grade connectors (AGCs). When and how to implement an AGC in Waze depends on circumstances.

This article suggests additional clarity to the Waze wiki regarding At-grade connectors, focusing on when they are and are not called for. It is a personal work for local purposes and is not offered nor reviewed as a contribution to the US or Global Waze wiki.

Applications

The rule for AGCs is "when in doubt, leave it out." For most intersections, separately mapped turn lanes confer no benefit. They add to the complexity of the display and substantially increase the effort required to verify connectivity, turn restrictions, directionality, name, etc. AGCs can also confuse routing for drivers who request a route while waiting at a stoplight on or near the AGC. If Waze snaps the driver to the AGC, it will offer a route assuming the driver is committed to the turn, which may not be the case.

Editors sometimes add AGCs because the satellite image suggests a separate turn lane when viewed with high magnification. This is never a good enough reason to map an AGC.

The following applications support use of an AGC.

Represent a physically separate road corridor

Ideally, AGCs represent physically separate, distinct road corridors that connect two larger roads at the same elevation. The physical corridor must be sufficiently isolated from the roads it connects that typical drivers would expect to see it explicitly depicted on the map, much like a freeway ramp. Update Requests from users that the map should show a connector warrant this application.

Prevent incorrect driver locating

Where frontage roads parallel very wide and intersecting highways for an extended distance, AGCs at the intersections may discourage Waze from snapping drivers to the frontage roads. This is uncommon.

Properly route side-road access

Sometimes side roads, especially parking-lot roads, connect near intersections in such a way that the side road can only be accessed from a separated right-turn lane. Drivers being routed to the side road must first diverge from the main road, while drivers emerging from the side road can only turn right and then continue along the right-turn path. Such a side road requires joining to an AGC to ensure proper routing.

Prevent "missing road" errors

Situations that do and don't throw the "missing road" Map Problem. Before the Parking-Lot Road was added, drivers transiting through the gas station triggered "missing road" Map Problems. Drivers transiting the main intersection, however, did not. The connectors at the intersection depart no further than 30 m from the center of the intersection. The path through the gas station departs from the intersection by at least 65 m. Therefore, At-Grade Connectors are not required at the main intersection to prevent MPs, but the Parking-Lot Road is.

When Waze observes repeated traffic through an area where no road is mapped, it may file a "missing road" Map Problem (MP) at the location. Driver paths that repeatedly "cut the corner" at an intersection can cause this error, but only when the corner-cutting path strays significantly from the intersection junction node. For example, the two short dedicated turn connectors physically present at the intersection of Pine Canyon and Jolon Roads (pictured) come no closer than 30 m to the junction node, but have not caused missing-road MPs. However, a path through the gas station that comes at closest 65 m to the junction node does, necessitating a Parking-Lot Road to prevent MPs (being a corner gas station, it will enjoy improved routing as well).

Waze has not released the distance threshold for triggering a missing-road MP. It appears to have changed over time, and it may change again. As of March 2015, even departures on the order of 20 m triggered MPs, resulting in numerous unfounded MPs at large city intersections. This article assumes that 50 m is a more likely long-term threshold.

Taking 50 m as the missing-road MP threshold, AGCs would then be appropriate to represent corner-cuts that come no closer than 50 m to the main intersection junction node. Corner-cuts that come closer to the junction node than 50 m would not warrant AGCs.

Uncommonly large bowtie junctions involve a tradeoff. While adding AGCs for the corner paths may prevent missing-road Map Problems, they may also result in an excessively cluttered and confused display. It is thought better in such cases to omit the AGCs and tolerate the occasional missing-road MP.

Note that, even if the separation of the turn path from the center of the intersection does not warrant an AGC, an AGC may still be called for to advance the timing of spoken turn alerts as described below.

Advance timing of spoken turn alerts

By advancing the location of the turn on the Waze map, AGCs advance the timing of turn alerts issued to drivers. In most cases the default alert timing is adequate, but in complex situations, advancing the alert may help prevent missed turns. Such situations can include:

  • connectors departing from highways of three or more lanes in one direction;
  • an uncommonly early turn commitment due to extended road striping or physical barriers;
  • limited visibility of the upcoming intersection; or
  • Update Requests complaining of inadequate alert timing.

Note that, even if inspection suggests no advance of the turn alert is necessary, an AGC may still be warranted to prevent "missing road" errors as described above.

Assessing the need for advanced alerts at complex intersections

When considering an AGC to advance a turn alert at a complex intersection, concern should focus on the penultimate, not the final, voice instruction. Final turn alerts at complex intersections almost always come too late for drivers who missed the previous alerts, and the editing community generally does not modify the maps to accommodate those situations. However, if the penultimate voice instruction would arrive too late for a driver to reach the correct turn lane, that would warrant an AGC for the purpose of advancing the turn alert.

A simple scoring system using "complexity points" can help assess the need for advanced alerts using AGCs. Measure the distance between the intersection junction node and the "commit location" where a driver must commit to a dedicated turn lane, and, for every full 75 m of distance involved, add one point. Then add another point for every lane change, worst-case, that an approaching driver would have to make to be in the correct through lane to depart for the turn; do not include the dedicated turn lane itself. If the resulting score is three or less, advancing the turn alert is almost certainly unnecessary. If the score is four or more, it may be appropriate to advance the turn warning with an AGC. As a rough rule of thumb, the departure junction of the AGC may be moved up by 75 m for every point over three.

This scoring system is a guideline only. The actual necessity for advancing turn alerts can depend on additional factors such as an uncommonly early commit location (more than 225 m from the intersection), a pattern of heavy but high-speed traffic, poor intersection visibility, other nearby turns that the driver might confuse with the desired turn, and as always, user reports of inadequate alert timing.

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