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* Update Requests complaining of inadequate alert timing. | * 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 AGCs 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 community generally does not modify the maps to accommodate those situations. If the penultimate voice instruction would arrive too late for a driver to reach the correct turn lane, however, that would warrant an AGC for the purpose of advancing the turn alert. The following scoring system using "complexity points" can help assess this need. | |||
Measure the distance between the intersection junction node and the "commit point" 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 through lane approaching the intersection; do not count turn lanes. If the resulting score is greater than four, it is 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 four. | |||
{{Clear}} | {{Clear}} | ||
Revision as of 06:38, 12 December 2014
When traffic moves between two roads that are at the same grade, these connecting segments are not technically ramps to Waze (unless it falls into one of the Exceptions listed below). Implementing an at-grade connector (AGC) in Waze depends on circumstances.
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
Tracks that appear to Waze to be "cutting the corner" may cause Waze's automated missing-road detection algorithms to flag a Map Problem. In tests in early 2014, a "corner cutting" path straying as far as 30 m from a junction was not enough to throw this error, but a path straying 65 m was. The actual threshold is unknown, but 50 m may be a good reference. Thus, adding At-Grade Connectors to corner-cuts that come no closer than 50 m to the main roads' intersection junction node is encouraged. Note that in some cases, such as large bowtie junctions, doing so may result in an excessively cluttered and confused display and it is thought better to omit the AGC and tolerate the occasional missing-road Map Problem.
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;
- uncommonly early "commit points" 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 AGCs 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 community generally does not modify the maps to accommodate those situations. If the penultimate voice instruction would arrive too late for a driver to reach the correct turn lane, however, that would warrant an AGC for the purpose of advancing the turn alert. The following scoring system using "complexity points" can help assess this need.
Measure the distance between the intersection junction node and the "commit point" 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 through lane approaching the intersection; do not count turn lanes. If the resulting score is greater than four, it is 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 four.
Road type
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 listed below.
The connector segment's type should be set based on the lowest of the types of roads it connects.
- Ex: Street to Minor Highway should be Street type.
- Ex: Minor Highway to Primary Street should be Primary Street type.
- Ex: Primary Street to Primary Street should be Primary Street type.
Example:
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.
Road name
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.
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.
Geometry
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.
Turn restrictions
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.
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.
AND, at the end of the connector, the left turn must be restricted:
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:
Exceptions
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This revision of a section is currently undergoing modifications. The information presented should be considered a draft, not yet ready for use. Content is being prepared by one or more users. Do not make any changes before you post a message in this forum. |
Median U turn intersection (MUTI)
The median crossing segments in a median U turn (aka "Michigan left") intersection should be set to the Ramp type.
Restricted crossing U turn (RCUT) intersection
The median crossing segments in a restricted crossing U turn (aka "J turn" or "Superstreet") intersection should be set to the Ramp type.
Displaced left turn (DLT) intersection
The crossover left turn lanes and the resultant elongated right turn lanes in a displaced left turn (or "continuous flow") intersection should be set to the Ramp type.
Jughandle
Jughandle segments should be set to the Ramp type.
Signed, numbered exit
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 instruction for Exit Right rather than Keep Right or Turn Right, this connector needs to be a ramp.
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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). |