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

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.

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?

top_gun_de wrote:These differences show why it's no possible to make global stAndards when there is no global standard for road construction, traffic rules and driver's habits.

I agree. I think my personal confusion over the issue stems from my lack of understanding of the significance of the global wiki pages. In this particular case, the Junction Style Guide/Interchanges page (which is nominated for Wazopedia Global Wiki) offers a clear, easy-to-understand rule, and our Canada wiki offers no guidance to suggest that our country standards differ from the global wiki's suggestion. Further investigation led me to understand even the Canadian champs differ in their opinions and approach, and freeway ramps across the country vary according to the individual editor's proclivities. We don't appear to have an agreed upon standard, and I can't really find much evidence that the editing community has even had much of a discussion about it. One of our champs mentioned that in closing over 10,000 URs, he's only encountered one or two complaints about the timing of exit ramps, so in the end, maybe this is much ado about nothing, and it really doesn't matter much where you place the junction node, as long as it's more or less right.

Still, though, the wiki offers a crystal clear rule, and I haven't heard from anyone yet that likes or follows this rule closely. Perhaps it doesn't actually represent the 'best' base case guidance that should be offered to editors... hence why I would be interested in knowing what edits have been proposed for this page.

Best regards
codgerd

Kayos_On_The_Road wrote:I believe the junction node where the solid line starts is by far the easiest and most consistent method of editing and should be applied across North America.

I find this to be a logical, easy, and consistent standard and would be happy to embrace it. It's not, as has been noted, the current wiki guidance. @kentsmith9 indicated there were proposed changes to this part of the Junction Style Guide wiki page. Is there any way to see what these are?

kentsmith9 wrote:At one time Sketch was doing a bunch of changes to JSG and there were many subpages created with works in progress last year. I lost track of where they went in their progress to get merged back together in a new page.

Is anyone currently spearheading the main JSG?

As far as I can tell, sketch's draft page for the JSG/Interchanges is here. I don't know if this represents the most recent version, but there are no apparent changes to the "Ramp geometry and complexity" section from the version currently in the wiki.

As it appears that the Canadian champs are more or less in agreement as to what the guidance should be for Canada, I'm going to lobby for us to make changes to our Canada wiki, as that appears to be easier than getting guidance from the global page.

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.

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.

… where a U turn is not allowed, but both of the left turns that make up that U turn are allowed separately, one of the following alternate [sic] intersection methods may be used.

What are the alternatives?

Does this mean that segment length less than 15 m is not a way to prevent a U-turn?