Author Topic: NV: I-15 Exits 43/44 & other missing exits  (Read 290 times)

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Offline rickmastfan67

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NV: I-15 Exits 43/44 & other missing exits
« on: January 19, 2023, 07:03:58 am »
So, NVDOT has given this area split exit numbers.  43 going NB, and 44 going SB.  Technically, since each set of ramps serve different roads (43 - D St) (44 - NV-578), should we add a separate exit #43 in I-15's file? https://goo.gl/maps/XambNw7qGmzzd9jr5

Doing this would also bring up an interesting situation for US-93 (which is along I-15 here).  US-93 swaps freeways I-15 -> I-515 (Future I-11) at Exit #42.  However, where it truly joins I-15 is literately right above NV-578 @ Exit 44.  Because of this, Exit 43 is completely inaccessible by US-93 traffic.  So, it would be improper to have a 'I-15(43)' in US-93's file.  So, the true mulitplex between the 2 would start @ Exit 44 instead of Exit 42.

=====

Just also noticed we're completely missing 3 other new exits on I-15 in the Las Vegas area.
29 - Star Ave (opened between July '19 & March '21)
30 - Cactus Ave (opened between June '14 & June '15)
HOV - Neon Gateway (between exits 40 & 41)

Offline oscar

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #1 on: January 22, 2023, 12:26:13 am »
So, NVDOT has given this area split exit numbers.  43 going NB, and 44 going SB.  Technically, since each set of ramps serve different roads (43 - D St) (44 - NV-578), should we add a separate exit #43 in I-15's file? https://goo.gl/maps/XambNw7qGmzzd9jr5

Doing this would also bring up an interesting situation for US-93 (which is along I-15 here).  US-93 swaps freeways I-15 -> I-515 (Future I-11) at Exit #42.  However, where it truly joins I-15 is literately right above NV-578 @ Exit 44.  Because of this, Exit 43 is completely inaccessible by US-93 traffic.  So, it would be improper to have a 'I-15(43)' in US-93's file.  So, the true mulitplex between the 2 would start @ Exit 44 instead of Exit 42.

My inclination is to make this a less interesting situation, by leaving exits 42 and 44 as is and ignoring exit 43 (or maybe adding it only to the I-15 file, and putting up with the false broken concurrency) -- the exit 43 and 44 points are only about 0.14 mile apart. The entire area has wonky exit numbering due to exit braiding, most notably where exit 42's SB ramp is well north of the exit 42 and 43 NB ramps. This kind of exit braiding throws a wrench into exit label perfection, and I'd rather not try.

When I first cleaned up the exit labels for the Las Vegas freeways when I took over maintenance of Nevada routes, I treated I-15 exits 43 and 44 as a single interchange, with a single waypoint 44 positioned to provide a good graph connection with NV 578. As you note, an exit 43 waypoint would be for an unnumbered road, no graph connection needed. Ditto NV 579 (Bonanza Rd.), which crosses under I-15 and US 93 just north of the I-15/I-515/US 93/US 95 interchange, with no ramps connecting to any of those routes.

I still need to address the missing exits you noted, which fortunately are all south of the I-15/US 93 concurrency.
« Last Edit: January 22, 2023, 05:10:08 pm by oscar »

Online yakra

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #2 on: January 28, 2023, 09:32:41 am »
https://en.wikipedia.org/wiki/Two-cent_piece_(United_States)

My first thought = keeping 43/44 1PPI & adding a hidden point to break the concurrency -- autoshape puts it here, and hot damn if that's not just about exactly where a theoretical Exit 43 would go.

Which leads me to what was already my 2nd thought; if adding a point anyway, why not add Exit 43 <shrug>. If you don't want the route traces to visibly diverge in mapview, a hidden point could be added to US93 offset by 0.000001.
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Offline oscar

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #3 on: January 28, 2023, 11:35:23 am »
^ I don't see a need to "break the concurrency". US 93 follows about the same path through the "Spaghetti Bowl" interchange in Las Vegas (Reno has its own "Spaghetti Bowl") as I-15 SB then US 95 SB, or the reverse for NB traffic. Just those US 93 ramps skip past exit 43.

Also, while US 93 NB and SB ramps skip past exit 43, if you take US 95 SB to US 93 NB  there are ramp connections to exit 43 for that movement (but not vice versa).

My current draft has exits 43 and 44 as separate, and both in the I-15 and US 93 route files. I can see removing exit 43 from both route files on 1PPI grounds, so long as 44 stays as is for its graph connection to NV 578. But adding a shaping point to break the US 93 concurrency complicates things, counter to the point of 1PPI favoring waypoint simplification. Considering the interchange is called the "Spaghetti Bowl" for a reason, I would not chase perfection here.

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #4 on: January 28, 2023, 12:03:16 pm »
^ I don't see a need to "break the concurrency". US 93 follows about the same path through the "Spaghetti Bowl" interchange in Las Vegas (Reno has its own "Spaghetti Bowl") as I-15 SB then US 95 SB, or the reverse for NB traffic. Just those US 93 ramps skip past exit 43.
Fair enough; I can see the logic here too. "Rounding off" traveling on a long ramp or frontage road to traveling on the main route itself is consistent with the very idea behind 1PPI, and with the Where the centerlines would cross if it were an at-grade intersection with the same shape rule.

Also, while US 93 NB and SB ramps skip past exit 43, if you take US 95 SB to US 93 NB  there are ramp connections to exit 43 for that movement (but not vice versa).
I see it a bit differently; that movement connects to I-15, proceeds along for a little ways, then joins US93. But that's all academic innit. 8)

My current draft has exits 43 and 44 as separate, and both in the I-15 and US 93 route files. I can see removing exit 43 from both route files on 1PPI grounds, so long as 44 stays as is for its graph connection to NV 578. But adding a shaping point to break the US 93 concurrency complicates things, counter to the point of 1PPI favoring waypoint simplification. Considering the interchange is called the "Spaghetti Bowl" for a reason, I would not chase perfection here.
Just not adding 43 seems to more closely align with "leaving exits 42 and 44 as is and ignoring exit 43" and not seeing a need to "break the concurrency". Maybe just go no-build here, and not commit the addition of 43 if it's not too late?
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Offline neroute2

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #5 on: January 28, 2023, 03:43:38 pm »
Looks like 1PPI should apply to the diamond at D and Washington. There is clear half access between US 93 and the diamond, so there's no need to separate any overlap.

Offline oscar

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #6 on: January 29, 2023, 11:18:32 pm »
Looks like 1PPI should apply to the diamond at D and Washington. There is clear half access between US 93 and the diamond, so there's no need to separate any overlap.

Thanks. Yet another reason to remove exit 43.

It's not too late for me to pull in the change.

Online yakra

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #7 on: January 30, 2023, 08:35:38 am »
Looks like 1PPI should apply to the diamond at D and Washington.
True. Only 0.14 mi apart as Oscar notes above.

There is clear half access between US 93 and the diamond, so there's no need to separate any overlap.
Faulty logic. The wording implies a causal relationship, when there is none. These 2 items are unrelated. Half access here has no bearing on what happens to the SW, between D St and US95.

Regardless, I've said my piece on that upthread, and Oscar's said his.
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Offline neroute2

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #8 on: January 30, 2023, 12:47:22 pm »
There is clear half access between US 93 and the diamond, so there's no need to separate any overlap.
Faulty logic. The wording implies a causal relationship, when there is none. These 2 items are unrelated. Half access here has no bearing on what happens to the SW, between D St and US95.
Half access is always enough to add a graph connection.

[edit] Are you suggesting putting graph connections at both interchanges, but breaking the overlap in between? WTF?
« Last Edit: January 30, 2023, 12:53:09 pm by neroute2 »

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #9 on: January 30, 2023, 08:52:05 pm »
Half access is always enough to add a graph connection.
Generally, yes. Notwithstanding obvious exceptions like trumpets etc. of course.
I believe the strictest interpretation of the manual would have one point on I-15, midway between D St & NV578, and another point in the NV578 centered on the roadway itself, so no graph connection. That said though, A lot of people seem to be moving away from this in favor of having a graph connection, and putting a point "off-center" on one route if there's another route in the HB, at junctions like this one. Which makes sense, really. Maybe it's time to update the manual, mumble mumble...

[edit] Are you suggesting putting graph connections at both interchanges,
If by "both" you mean the I-15/US95 junction and Exit 44, sure...

but breaking the overlap in between? WTF?
If it were my state to maintain, maybe, sure, yeah. (Though I did concede above that I can see the logic in not doing so as well. NV is Oscar's state to maintain as he sees fit, and so I can't & won't fight it all the way to the end of the Earth.)
I-15 & US93 are clearly carried on different physical roadways here.
For similar examples in my states to this idea, point mapview at
Providence, 95/195 jct
or a more mind-bending example & possibly my personal favorite, Fall River, @ US6, MA79 & MA138.
Select "Color by Concurrencies". The effects are most visible with "Highlight None".
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Offline oscar

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #10 on: Yesterday at 03:57:21 pm »

Offline rickmastfan67

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #11 on: Yesterday at 08:37:18 pm »
Half access is always enough to add a graph connection.
Generally, yes. Notwithstanding obvious exceptions like trumpets etc. of course.
I believe the strictest interpretation of the manual would have one point on I-15, midway between D St & NV578, and another point in the NV578 centered on the roadway itself, so no graph connection. That said though, A lot of people seem to be moving away from this in favor of having a graph connection, and putting a point "off-center" on one route if there's another route in the HB, at junctions like this one. Which makes sense, really. Maybe it's time to update the manual, mumble mumble...

I-410(US-281/TX-130) & TX-Spur-122 says hi Yakra. ;)

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Re: NV: I-15 Exits 43/44 & other missing exits
« Reply #12 on: Today at 08:08:55 am »
I responded in that thread, with a link to the manual.
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