Author Topic: AR I-55(7) broken multiplex  (Read 464 times)

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Offline yakra

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AR I-55(7) broken multiplex
« on: January 31, 2019, 12:52:34 am »
Looking at I-55(7)/AR77.
I-55's concurrency with I-40,US61,US64,US79 is broken.

This interchange complex and its associated multiplexes were a bit of a PitA to iron out in Operation Arkansas Cleanup.
At that time, I chose to call it part of the Exit 277 interchange, in order to maintain the concurrencies, and because I-40 & US79 have no access there.

How to handle it? Yecch...
I'm thinking maybe remove the point from I-55, and leave it in place on AR77? There are similar situations in TX where a route intersects another's frontage road(s), with no direct access to the route itself. (Meh, it's imperfect, but so are double trumpets.)

Offline froggie

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Re: AR I-55(7) broken multiplex
« Reply #1 on: January 31, 2019, 09:32:23 am »
A few possible solutions:

- If you keep the point, you'll need to add it to US 61 and US 64 since both routes are concurrent with I-55.
- You could remove the point entirely for the freeway and just leave it on AR 77 as you suggest.  I would concur with this solution.
- Add it to US 61/US 64 as noted above and make it a hidden point on I-40/US 79.  Sure, you may incur a case where someone coming south on I-55 and exiting there would then log a concurrency with I-40/US 79 when they were never on I-40, but at last check the number of users actually using the waypoint for Exit 7 is a nice round number (literally).

Offline mapcat

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Re: AR I-55(7) broken multiplex
« Reply #2 on: January 31, 2019, 02:05:27 pm »
I'll add the point to US 61 & US 64. Not sure what would be served by adding it as a hidden point on the others, except for preserving a concurrency that isn't really a concurrency there.
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Offline mapcat

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Offline Duke87

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AR: I-40/I-55 (and US61/64/79) concurrency broken
« Reply #4 on: April 15, 2019, 07:51:22 pm »
I-40 point "277" and I-55 point "8" are at the same coordinates and should mark the beginning of the concurrency between these two routes. But the concurrency doesn't detect until I-40 point "278" / I-55 point "278(40)", because of the existence of an intervening point "7" on I-55 that does not exist on I-40.

That "7" point corresponds to a single ramp that is accessible only from I-55 southbound. So it is correctly not a point for I-40 except that this breaks the concurrency.

Seems to me one of two things should be done to fix this:
Option 1) Add "+7(55)" to I-40 as a hidden point, with the same coords as the point on I-55. This would generate a visible/hidden collocation error that would need to be marked as FP, and a "+7(I-55)" point would also need to be added to US 79.
Option 2) Just get red of the "7" point on I-55 (it is not currently in use) on the grounds that it's more or less within the footprint of the I-55/I-40 junction, and thus the one point per interchange policy can be invoked. This would also require eliminating "I-55(7)" from US 61 and US 64.
« Last Edit: April 15, 2019, 07:57:02 pm by Duke87 »

Offline rickmastfan67

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Re: AR: I-40/I-55 (and US61/64/79) concurrency broken
« Reply #5 on: April 15, 2019, 11:09:26 pm »
Oof, this is an annoying one.

I'm going to have to side IMO with Option 1.

Option 1) Add "+7(55)" to I-40 as a hidden point, with the same coords as the point on I-55. This would generate a visible/hidden collocation error that would need to be marked as FP, and a "+7(I-55)" point would also need to be added to US 79.

Reason?  You have AR-77 in the mix there, and thus, can't invoke the "one point per interchange policy".  If it wasn't there, I could side more with option 2.

Only difference with US-79 is that I would label the hidden point as "+I-55(7)" to keep it naming wise in sync with the rest of the multiplex.
« Last Edit: April 15, 2019, 11:12:42 pm by rickmastfan67 »

Offline yakra

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Re: AR I-55(7) broken multiplex
« Reply #6 on: April 15, 2019, 11:46:27 pm »
Topics merged.

Option 2) Just get red of the "7" point on I-55 (it is not currently in use) on the grounds that it's more or less within the footprint of the I-55/I-40 junction, and thus the one point per interchange policy can be invoked. This would also require eliminating "I-55(7)" from US 61 and US 64.
This gets my vote. It's what I did for Operation AR Cleanup (see upthread).

- You could remove the point entirely for the freeway and just leave it on AR 77 as you suggest.  I would concur with this solution.
:D
« Last Edit: April 15, 2019, 11:59:58 pm by yakra »

Offline mapcat

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Re: AR I-55(7) broken multiplex
« Reply #7 on: April 24, 2019, 09:12:30 am »
This is not a broken concurrency. This is intentional. There needs to be a graph connection between AR 77 and I-55/US 61/US 64. Adding a hidden point to I-40/US 79 just to make things look nicer is unnecessary IMO.
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Offline yakra

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Re: AR I-55(7) broken multiplex
« Reply #8 on: April 24, 2019, 03:51:22 pm »
This is not a broken concurrency.
Aah, but it is though. I-40,US79 and I-55,US61,US64 are fully on the same carriageways east of here, and split apart west of here, at the 40/55 interchange (I-40@277&I-55@8&US61@I-40(277)&US63@I-40(277)&US64@I-55(8)&US79@I-40(277)).
HDX-Lite link: http://yakra.teresco.org/tmtools_demos/tmg2html/AR-region.tmg.html
Search for "35.171809" and click on the result in the table; that will pan you to the area. You'll see two different overlays: a green one for I-40,US79 and a magenta one for I-55,US61,US64.

There needs to be a graph connection between AR 77 and I-55/US 61/US 64.
I disagree: there does not need to be a graph connection.
Plenty of routes won't have them, the most obvious canonical examples being double trumpets, short connecting (quadrant) roads, etc.

Some similar endpoints in Texas:
• The most obvious  cut-n-dry example is TXSpr93. US69 has no point here, because a traveler would enter/exit the highway at one of the full diamonds at HigAve to the south & FloAve to the north.
TX78 is similar, though the "overlap" in the westbound direction is a bit more of a gray area.
TXSpr104 is missing one of the frontage roads, and interchanges are farther off.

Other less directly applicable cases:
• Ends at one frontage road, with no direct half-interchange or grade-deparated crossing
Ends at diamond ramp
• Splits off as effectively one ramp
• Ends as frontage road, becoming parallel to fwy


Adding a hidden point to I-40/US 79 just to make things look nicer is unnecessary IMO.
Beyond just making it look nice; IMO concurrencies are important; it's starting to get into messing with people's stats.
And someone using the point on I-55 etc. could get confused when opening up I-40 etc. in the HB; IMO this should be minimized.

I don't propose the hidden point, but rather leaving the point out of I-55 & pals. My justification for this is above.
Duke87's proposed "Option 2" (indeed, being "within the footprint of the I-55/I-40 junction" was part of the reason I originally removed it during Operation AR cleanup), with froggie on board as well.

Offline mapcat

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Re: AR I-55(7) broken multiplex
« Reply #9 on: May 26, 2019, 04:31:07 pm »
@yakra: Thanks for the additional explanation. Sorry for the delay; the last month has been unusually busy for me.

First, I'm disappointed that you think I was unaware of HDX or how to use it properly. I am a frequent user of HDX and fully realize how it seems to indicate a problem here, hence the topic.

I-40 and I-55 are not actually concurrent here. I-55 exit 7 is within the footprint of the I-40/55 split, but the point where I-55 and AR 77 cross is located to the east of the center of the split. The I-40/I-55 point is where it needs to be according to the CHM guidelines, as is the I-55/AR 77 point. It is messy because reality is messy here.

I acknowledge that you disagree that graph connections need to exist here. CHM guidelines were written prior to Jim's assumption of the project, and collaborators have occasionally mentioned Tim's insistence that graph connections were not a priority. However, Jim has indicated on numerous occasions that graph connections are helpful for the METAL project, and has demonstrated his interest in this by creating tools for us to use to identify NMPs and other errors. The fact that he refers to them as errors tells me that minimizing them should be a priority. Granted, there are cases where graph connections can't be made for one reason or another. It's my opinion that this is not one of those cases. The Texas examples you bring up are different (lack of direct access, or different exit numbers from opposite directions). They are much more like I-40 exit 276 (from eastbound I-40 to AR 77 from the opposite side of the split), which correctly does not have a graph connection to AR 77 since access is made via a long stretch of frontage road. Nevertheless, even if your examples were identical to this one, I would be comfortable with how you handled them because they are consistent with the guidelines, such as they are.

(Regarding your TXSpr93 example, it seems that the US69 point would be more properly labeled US69/287 or US69/96.)

Concurrencies certainly are important. However, I fail to see how this could be "messing with people's stats" any more than the alternatives.

Example: a user who has never travelled on I-40 takes I-55 southbound to exit 7 and continues on AR 77. As things are set up currently, she would get credited for mileage on I-55 and AR 77 but not I-40, with the benefit of having a link to AR 77 show up from the I-55 page in the HB. She would not receive any credit for travelling on I-40.

If Exit 7 were eliminated, the user would either have a gap in her maps and a few tenths of a mile less of I-55 than she had actually travelled, or might instead feel the need to claim mileage all the way to the next waypoint south (I-40 exit 278). Either way, that would mess with her stats, in my opinion. Likewise, if Exit 7 was added as a hidden point on I-40, the segment of I-55 between waypoints 7 and 8 would also count as mileage on I-40, which she had technically not travelled. The concurrency detector would not give her any additional mileage, but she would have a short distance of I-40 showing up in her table, which would also mess with her stats.

In summary, I believe that the slight increase of mileage in Arkansas caused by not treating I-40 and I-55 as concurrent between I-40 points 277 and 278 is no more incorrect than the slight decrease of eliminating the point for the I-55/AR 77 junction. As a result, I am leaving things as they are here.
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