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User:Nagamasa/Junction box

530 bytes added, 5 months ago
Undo revision 168244 by Nagamasa (talk)
Junction boxes are considered only by the routing server. Junction boxes have no visibility in the client or on the live map. Junction boxes do not affect the search engine; the origin or destination of route may be contained in a junction box.
==When to use==
A junction box is a versatile tool that can help improve the accuracy of the map data. However, if problems are easily solved with other features such as [[Glossary#Turn_Restriction|turn restrictions]], then a junction box should not be used.
 
Appropriate times to use a junction box:
# [[Junction box#Controlling turns|To allow or disallow paths across multiple junction nodes]]:
#* Where there can be two entrances to same exit path, but a route is prohibited. A simple turn restriction cannot adequately set the correct restrictions.
#* In an H-intersection, when u-turns are allowed in one direction, but prohibited in the opposite direction. Previously, [[Routing penalties/Controlling U-turn penalties|u-turn penalties]] & micro doglegs were used to break the u-turn prevention in one direction. There's no need to eliminate these, but a junction box would be appropriate for these intersections going forward.
#* When the cross segment is less than {{:Routing_penalties/U-turn_minimum|less}} due to the geometry of the intersection, and u-turn prevention needs to be overwritten to allow u-turns.
# [[Junction box#Navigation instructions|To set a turn instruction override]] in these situations:
#* For a particular route, when only a single turn instruction is desired at the first junction node, and no additional instructions at subsequent junctions.
#* When an early turn instruction is desired, without drawing an additional segment.
# [[Junction box#Improving data collection|To better collect traffic data]] when there is a speed differential between traffic lanes through multiple junction nodes, such as:
#* At-grade connectors (AGC) and parking lot roads cutting an intersection area into multiple segments and nodes
#* Auxiliary lanes: entry ramps that extend to the next exit ramp: drivers that are merging on/off the freeway will have a different set of speeds than those that were already on the freeway and continuing on it
#* Regular, long backups: backups that extend past turn pockets and exit ramps into lanes for through-traffic lanes
==Improving data collection==<!-- The original page, specifically this entire section was reviewed 2015-11-10 by staff Ohad and confirmed as accurate. Staff quote "it looks really great, comprehensive and correct". -->
[[File:Junction Box 3.png|right|75px|link=https://wazeopedia.waze.com/wiki/USA/File:Junction_Box_3.png]]Let's look at how a complex intersection can skew [[Routing server#Turn delays|turn delay]] transition speed data. Take the following intersection for example. It seems at first glance like a pretty simple intersection, but if it usually experiences heavy traffic this intersection could be collecting bad data.
*'''Enabled u-turn turn restriction on a two way segment''' - Note that having u-turn turn restriction(s) enabled on a two way segment inside of the junction box will increase the amount of paths and can lead to the saving error message.
===Adding complexity===Adding segments or junction nodes to an intersection to workaround the "one connection for every entry/exit pair" and "no more than 16 connections per node" limitations is not recommended. If such a workaround is required, please consult with your [[Country Manager#Coordinators|country]] manager or [[Regional Coordinator|regional coordinator]].==When * Segments connected to use==Junction boxes are suitable only for specific locations where the above-listed functions of junction boxes are required. An example would be to prohibit the U-turn in one direction but allow it in the other such have some attributes that a {{:Routing_penalties/U-turn_minimum|less}} center segment is forcing a necking down of the normal flow of a road and micro-doglegs are used to allow the one direction's U-turn. If problems with data collection or turn restrictions are experienced then, a junction box may cannot be used to solve edited without first deleting the problem. If problems are easily solved with other features such as [[Glossary#Turn Restriction|turn restrictions]], then a junction box should not be used. For routes through H intersections that have one u-turn allowed and one u-turn prevented then use a simple junction box instead of or [[Routing penalties/Controlling U-turn penalties|U-turn penalties]] and using micro doglegs to break the u-turn prevention in one direction. Existing intersections with micro doglegs or abnormal geometry can be changed to a junction box when being edited for other reasons, but you shouldn't go out hunting to eliminate all of them if they are already working properly.
Appropriate times to use === Edits not allowed when editing ===Certain properties of segments that are a part of the junction box cannot be edited without first removing the junction box:*Have Direction of travel (two entrances to same exit path but way/one route is prohibited so can't use a simple Turn restrictionway)*Have u-turn allowed Turn restrictions that are not in one direction of an H-intersection, but prohibited in anotherthe junction box for segments that extend outside the junction box's boundaries*To override u-turn prevention when Moving the cross segment is less than {{:Routing_penalties/U-turn_minimum|less}} due to the geometry location of the intersectionsa junction node within a junction box*Traffic backs up through multiple junction nodes from Edits that change a direct left turn, an at-grade connector (AGC), an exit ramp, segment's identification number** Adding or even through travel caught at deleting a traffic light; where junction node inside the back up adversely affects junction box** Adding or deleting a junction node on a segment that extends outside the timing for junction box (ex. You have to delete the traffic junction box to add a parking lot road to a segment that is moving*To better collect traffic data on intricate intersectionsincluded in a junction box)
Junction boxes To edit these properties, you must first delete the junction box, make the edits, then re-create another limitation that should be considered:*Segments connected to the junction boxes have some attributes that cannot be edited without first deleting box. The data associated with the junction boxshould not change with if the segments' identification numbers also do not change. With this complication, use judgement before creating junction boxes everywhere.
Edits not allowed are:===Adding complexity===*Direction of travel (two way/one way)*Turn restrictions that are not in the junction box for Adding segments that extend outside the junction box's boundaries*Moving the location of a junction node within a junction box*Edits that change a segment's identification number#Adding or deleting a junction node inside nodes to an intersection to workaround the junction box#Adding or deleting a junction "one connection for every entry/exit pair" and "no more than 16 connections per node on a segment that extends outside the junction box (ex" limitations is not recommended. You have to delete the junction box to add a parking lot road to If such a segment that workaround is included in a junction box) For these reasonsrequired, junction boxes should not be used for every intersectionplease consult with your [[Country Manager#Coordinators|country]] manager or [[Regional Coordinator|regional coordinator]].
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