[Page Update] Junction Style Guide

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Re: [Page Update] Junction Style Guide

Postby ct13 » Fri Sep 04, 2015 9:41 pm

I think a helpful addition to this page would be something that explains the road type classification on segments that are part of divided road intersections. It would be provide instructions on how to assign road types inside of the intersections, similar to the roundabout road type page.


"When road segments of 2 different types converge at divided road intersection, choose the highest road type of the parallel, intersecting segments. Doing so will ensure that high priority roads are not unduly pruned by the routing algorithm at an intersection."


Here is an extreme example of the type of graphic that could used to illustrate this point.

1.png
Junction pre-typed
(132.56 KiB) Downloaded 647 times

2.png
Proper road types
(125.05 KiB) Downloaded 647 times
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Re: [Page Update] Junction Style Guide

Postby PesachZ » Fri Sep 04, 2015 10:26 pm

ct13 wrote:I think a helpful addition to this page would be something that explains the road type classification on segments that are part of divided road intersections. It would be provide instructions on how to assign road types inside of the intersections, similar to the roundabout road type page.


"When road segments of 2 different types converge at divided road intersection, choose the highest road type of the parallel, intersecting segments. Doing so will ensure that high priority roads are not unduly pruned by the routing algorithm at an intersection."


Here is an extreme example of the type of graphic that could used to illustrate this point.

1.png

2.png

It' a good idea, and we should include guidance for median segments when they are not in a box junction as well.

Though I would argue that by our AGC rules in the US the two medians you set as MH, should really be mH. making them mh will have no detrimental on routing here.

The issue will be that the guidelines fo this kind of thing varies by country. Perhaps it is better placed in the page for Median Uturns, and have that page expanded to cover all median typing in the USA.
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Re: [Page Update] Junction Style Guide

Postby ct13 » Fri Sep 04, 2015 10:55 pm

Maybe we can spin this off into a new topic or move to the correct place?

PesachZ wrote:Though I would argue that by our AGC rules in the US the two medians you set as MH, should really be mH. making them mh will have no detrimental on routing here.


If we followed AGC rules, it seems like the turn from the PS to the MH or the mH would be adversely effected by having the median segment set as street type. I think that having it be the highest segment type is a much simpler rule than following the AGC rules except when the road group changes; for instance, "when MH and street meet, defer to the highest type, but when 2 types of highways meet, pick the lowest of the two." would be much more confusing for a negligible (or arguably worse) change in routing. One size fits all rules are always easier to remember and since there is a bigger downside associated with choosing a lower road type than a higher one, this would err on the side of caution.

PesachZ wrote:The issue will be that the guidelines fo this kind of thing varies by country. Perhaps it is better placed in the page for Median Uturns, and have that page expanded to cover all median typing in the USA.


That sounds like a good place for it. Additionally, a link from the Road Types/USA page from this sentence would also seem appropriate.

Wiki wrote:Special rules are used to determine the road types of roundabouts and at-grade connectors.
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Re: [Page Update] Junction Style Guide

Postby PesachZ » Sun Sep 06, 2015 5:16 am

ct13 wrote:Maybe we can spin this off into a new topic or move to the correct place?

PesachZ wrote:Though I would argue that by our AGC rules in the US the two medians you set as MH, should really be mH. making them mh will have no detrimental on routing here.


If we followed AGC rules, it seems like the turn from the PS to the MH or the mH would be adversely effected by having the median segment set as street type. I think that having it be the highest segment type is a much simpler rule than following the AGC rules except when the road group changes; for instance, "when MH and street meet, defer to the highest type, but when 2 types of highways meet, pick the lowest of the two." would be much more confusing for a negligible (or arguably worse) change in routing. One size fits all rules are always easier to remember and since there is a bigger downside associated with choosing a lower road type than a higher one, this would err on the side of caution.

PesachZ wrote:The issue will be that the guidelines fo this kind of thing varies by country. Perhaps it is better placed in the page for Median Uturns, and have that page expanded to cover all median typing in the USA.


That sounds like a good place for it. Additionally, a link from the Road Types/USA page from this sentence would also seem appropriate.

Wiki wrote:Special rules are used to determine the road types of roundabouts and at-grade connectors.

I don't argue street would be bad, when I suggested a chance to your proposal, I meant only to change those two MH medians to mH.

I'll explain better what I meant by the AGC rule.
The wiki article for AGCs now (which really reflects the US usage for them) is simplified. It only really discusses a single segment (the agc) connected to one segment on either side.
The rule is to use the lower of the two road types. The logic which leads to this rule is that no additional penalty or pruning will ensue while traversing the AGC. Since it is continuing the same type as either the preceding segment, or the segment afterwards.

In short the logic is What is the lowest type this can be without adding an additional penalty or pruning effect .

When you expand this logic to a more complex AGC connecting more than two segments we have to apply the same logic. The simple way to explain it is very similar to how we explain roundabouts typing.
  1. Assess each possible route through the segment.
  2. List the lower road type for each route.
  3. Choose the highest type on the list you made in step 2.

With this rule the two E-W medians in your box become mH, while the other two remain PS as you had them.

The same role can be applied to an AGC connecting 3, 4 or more segments with ease.

There is a thread in the NJ where we spent a long time hashing this out for use in guidelines for jughandles.

If this is at all unclear, let me know I can create images to better explain it.

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Re: [Page Update] Junction Style Guide

Postby codgerd » Fri Sep 18, 2015 3:54 pm

Hi all,

A discussion started recently on the Canada unlock forum as to best practice in terms of placing the junction node of an exit ramp. The wiki guidance on the Interchange page recommends placing the first geometry node of the ramp segment level with where the solid line starts at an exit i.e. at the last legal decision point to take the exit, and to put the junction node itself prior to this point such as to make a 10 - 15 deg angle with the roadway.

https://wiki.waze.com/wiki/Junction_Sty ... complexity

As (at least in Canada) it seems that in practice there is a wide range of configurations employed for ramp geometries and the wiki guidance is clearly not being followed in any consistent way, I raised the issue with my local champ mentor, who in turn raised it with the Canadian and US champs and routing experts.

I gather that the discussion is still ongoing, but it seems that the emerging consensus is that this may not in fact be the recommended guidance; rather, it seems that it should be the junction node itself that be placed at the last legal decision point, not the first geometry node of the ramp segment.

If they arrive at a full consensus on this, I suspect it will be brought to the wiki community's attention via other channels, but I thought I would raise the issue here to allow for any discussion that may be deemed appropriate.

Cheers
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Re: [Page Update] Junction Style Guide

Postby PesachZ » Fri Sep 18, 2015 9:47 pm

codgerd wrote:Hi all,

A discussion started recently on the Canada unlock forum as to best practice in terms of placing the junction node of an exit ramp. The wiki guidance on the Interchange page recommends placing the first geometry node of the ramp segment level with where the solid line starts at an exit i.e. at the last legal decision point to take the exit, and to put the junction node itself prior to this point such as to make a 10 - 15 deg angle with the roadway.

https://wiki.waze.com/wiki/Junction_Sty ... complexity

As (at least in Canada) it seems that in practice there is a wide range of configurations employed for ramp geometries and the wiki guidance is clearly not being followed in any consistent way, I raised the issue with my local champ mentor, who in turn raised it with the Canadian and US champs and routing experts.

I gather that the discussion is still ongoing, but it seems that the emerging consensus is that this may not in fact be the recommended guidance; rather, it seems that it should be the junction node itself that be placed at the last legal decision point, not the first geometry node of the ramp segment.

If they arrive at a full consensus on this, I suspect it will be brought to the wiki community's attention via other channels, but I thought I would raise the issue here to allow for any discussion that may be deemed appropriate.

Cheers
codgerd

I do agree that based on how the TTS timing is set up in the app, that the user will have a better experience if the junction node is at the gore ( the last legal point to make a lane change).
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[Page Update] Junction Style Guide

Postby DwarfLord » Sat Sep 19, 2015 4:18 pm

PesachZ wrote:...based on how the TTS timing is set up in the app, that the user will have a better experience if the junction node is at the gore

I have struggled for nearly a year with the question of where junction nodes should be located.

Originally I believed it best for editors to focus on the penultimate turn instruction. That is, we adjust junction nodes to ensure that the next-to-last voice instruction arrives in time for drivers to change lanes and otherwise prepare. I wrote local provisional AGC guidelines based on this penultimate-instruction focus.

Then other editors told me that Waze is notorious for never issuing any but the final instruction. One editor said his wife refuses to use Waze because the final instruction is the only one she hears and it always comes too late. From his perspective it was a non-starter to focus on the penultimate instruction since Waze so often fails to provide it.

This has not been my experience. But if it really is common that drivers only receive a final instruction and no other, junction nodes should be placed far enough ahead of the physical decision point so that the final instruction arrives in time to change lanes/whatever. For any but the simplest exit, that means advancing the junction node well before the gore.

So "how the TTS timing is set up in the app" really is the key question here. I hear conflicting driver experience and have no idea what to recommend.
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Re: [Page Update] Junction Style Guide

Postby codgerd » Mon Sep 21, 2015 6:47 pm

DwarfLord wrote:I have struggled for nearly a year with the question of where junction nodes should be located.
(...)
So "how the TTS timing is set up in the app" really is the key question here. I hear conflicting driver experience and have no idea what to recommend.

Newer editors (like myself) often take the guidance in the wiki as gospel, or, at any rate, as representing the distilled wisdom and consensus of the editing community. If the wiki offers clear and unambiguous guidance on an issue, I tend to follow it!
If in fact, as appears to be the case both here and from what I've heard from my local champ mentor, there is no real agreed upon consensus on the issue of placement of exit ramp junction nodes, and even very experienced editors and wiki-editors still feel unsure about the proper guidance, then surely the current (very clear and explicit) guidance should either be deleted or amended to include a statement to the effect that there is no consensus on the proper placement of junction node at this time, and to check with local-level mentors for best practise in ones local editing area? The wiki article could then offer the various options that have been proposed, rather than a very clear and easy-to-apply rule that is not at all universally followed.
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Re: [Page Update] Junction Style Guide

Postby top_gun_de » Wed Sep 23, 2015 6:00 pm

Speaking for my country, there has been a process over the years. We started with simple answers, and have arrived at a point where we apply something like "fuzzy-logic".

Some key factors which are relevant:

- the "turn now"-instruction shall never be so late that turning the wheel is illegal or unsafe.
- the turn now shall not be so early that there is confusion between alternative exits
- if traffic is expected to stand on the straight lane or the ramp (ie due to traffic lights), short ramps are preferable to reduce errors from misplacement after gps issues
- if ramps are preceded by distance poles, drivers appreciate a match of displayed data with real-world signs.

For us, that means that we start freewayramps shortly after the beginning of the striped line, and that we start ramps on major highways late if we expect drivers to stop for more than a few seconds. The rest is somewhere in between.

Your local mileage will vary, based on national or local customs.

Best regards,

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Re: [Page Update] Junction Style Guide

Postby codgerd » Thu Sep 24, 2015 3:21 pm

top_gun_de wrote:For us, that means that we start freewayramps shortly after the beginning of the striped line, and that we start ramps on major highways late if we expect drivers to stop for more than a few seconds. The rest is somewhere in between.


Interesting. So the accepted usage in Germany is to put the junction node at the start of the striped line (with exceptions as described in your post).

We have, therefore, two end-member solutions apparently in common usage:
1. junction node is placed at the beginning of the gore (where the striped line dividing the exit lane from the roadway changes to solid)
2. junction node is placed at the beginning of the exit lane, where the striped line first begins

and we have the current wiki guidance, which is in between these two solutions, although much closer to (1).

kentsmith9 tells me that changes have been proposed for this section of the wiki. Is there any way to view these proposed changes to see the new proposed guidance under consideration?
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