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National Boards => General Highway Talk => Topic started by: SkyPesos on January 23, 2021, 11:10:17 PM

Title: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 23, 2021, 11:10:17 PM
I'm not sure if there's already a guideline for exit number priority in interstate-interstate concurrencies in the MUTCD, but I'm guessing there isn't from all the inconsistencies I found in various examples around the country. I decided to create my own unofficial guidelines that makes the most sense to me, and is what I use in my fictional exit lists.

1) In concurrencies with a 2di and 3di, the 2di would have exit number priority: Examples: I-74 with I-275, I-95 with I-495, I-29 with I-435.
2) In concurrencies where one route clearly exits off at both ends of the concurrency, the through route would have exit number priority. Examples: I-75 with I-71, I-70 with I-71, I-76 with I-70, I-15 with I-80.
3) In concurrencies where one route clearly exits off on one end, but the other end isn't clear on which route looks like the exit because of lane count, angle of exit, left side placement, etc, the through route through the definite exit would have exit number priority. Examples: I-65 with I-70, I-75 with I-85, I-77 with I-64.
4) In concurrencies where one route exits off at one point, and the other exits off at the other point, the longer route in the state would have exit number priority. Examples: I-57 with I-70, I-75 with I-64. This is what I went off with in a fictional idea that involves an I-70 and I-95 concurrency (https://www.aaroads.com/forum/index.php?topic=28310.msg2563647#msg2563647).
5) In concurrencies where the exiting route can't be determined because of lane count, angle of exit, left side placement, etc, on both ends, the longer route in the state would have exit number priority.

Of course there are a couple of "rule breakers" examples around, like the I-90/I-94 concurrency in IL should be using I-90's exit numbers based on my guidelines. Part of the rule breakers are for historical reasons, like in the I-40/I-85 concurrency, that route was solely I-85 when it was first designated, and I-40 was added on later.

Would be interesting to see if anyone else have their own guidelines of sorts for exit number priority in interstate-interstate concurrencies, or any other exceptions to my guidelines.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: Revive 755 on January 23, 2021, 11:20:07 PM
The 2009 MUTCD does not specify which interstate gets priority.

Quote from: 2009 MUTCD 2E.31 Paragraph 16
Where numbered routes overlap, continuity of interchange numbering shall be established for only one of the routes (see Figure 2E-21). If one of the routes is an Interstate and the other route is not an Interstate, the Interstate route shall maintain continuity of interchange numbering.

As for exceptions to the rules in your post, the first rule has a few:

1) I-465 gets priority over I-74 around Indianapolis
2) I-694 gets priority over I-94 north of Minneapolis.
3) I-294 gets priority over I-80 south of Chicago

Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: I-55 on January 23, 2021, 11:34:35 PM
Your rule number 4 is the one I can think of the most examples of off the top of my head:

I-35/80
I-20/59 MS
I-40/65
I-40/24
I-40/75
I-40/55

you could also apply this to routes that have the higher mileage at the point of the concurrency. Including the examples above, I also know that the I-29/80 concurrency uses I-29's mileage despite it breaking all of the given rules.

Other exceptions for rule #1:

I-75/640
I-83/695
I-87/440 (historic reasons)

Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: ran4sh on January 23, 2021, 11:48:48 PM
Your rule 4 probably has a higher priority in practice. For example, I-20/59 in Mississippi, the only logical choice is to use I-59 because its mileage is higher at the point they meet. If I-20's miles were used then I-59 would possibly have overlapping exit numbers. Similarly, I-75/85 is almost certainly because I-75's mileage at that point is higher than anything I-85 reaches on its own in Georgia. And not because of interchange design.

As for I-40/85, at least on the Greensboro end, the interchange is designed with I-40 as the exit. This is because they had intended that I-40 would continue with I-85 to the interchange south of Greensboro, and the interchange where they split now, was intended as the exit for Business 40 & Business 85.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: Scott5114 on January 24, 2021, 01:42:30 AM
In Oklahoma, Interstate-Interstate concurrencies use the lower-numbered Interstate's exit numbers. Which is a fancy way of saying that in both instances of this occurring in the state, I-35's exit numbers are carried through. This means that I-40, which has the longest Interstate mileage in the state, has two exit 127s (one at Radio Road west of the OKC metro, and again at M.L. King/Eastern Ave in OKC, along the I-35 concurrency).
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: sprjus4 on January 24, 2021, 05:02:18 AM
Your rule 4 probably has a higher priority in practice. For example, I-20/59 in Mississippi, the only logical choice is to use I-59 because its mileage is higher at the point they meet. If I-20's miles were used then I-59 would possibly have overlapping exit numbers. Similarly, I-75/85 is almost certainly because I-75's mileage at that point is higher than anything I-85 reaches on its own in Georgia. And not because of interchange design.

As for I-40/85, at least on the Greensboro end, the interchange is designed with I-40 as the exit. This is because they had intended that I-40 would continue with I-85 to the interchange south of Greensboro, and the interchange where they split now, was intended as the exit for Business 40 & Business 85.
Either way, even with I-40 on the southern loop, I-85 still has the priority where I-73 / former I-40 exited off for the southwestern part of the loop.

On the eastern end of the I-40 / I-85 concurrency, I-40 also exits off with design favoring I-85 through traffic.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: GaryV on January 24, 2021, 07:03:16 AM
I-69 loses twice in MI:
-- On the west side of Lansing, I-96 exit numbers apply  (I-69 exits the main line at both ends of the concurrency with I-96 exit numbers)
-- In Port Huron, I-94 exit numbers apply (I-69 is exit 271 from I-94)
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: roadman65 on January 24, 2021, 07:23:42 AM
In Virginia I-64 loses twice with both I-81 and I-95.  It used to have no exit numbers in the state but the toll road in Richmond had sequential numbering from 1 to 17 at that time so only part of I-95 had numbers with a smaller part of I-64.

I-64 in Hampton once had a set counting up from the HRBT left over from when VA 168 was the sole route through Hampton.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: fillup420 on January 24, 2021, 08:18:13 AM
Your rule 4 probably has a higher priority in practice. For example, I-20/59 in Mississippi, the only logical choice is to use I-59 because its mileage is higher at the point they meet. If I-20's miles were used then I-59 would possibly have overlapping exit numbers. Similarly, I-75/85 is almost certainly because I-75's mileage at that point is higher than anything I-85 reaches on its own in Georgia. And not because of interchange design.

As for I-40/85, at least on the Greensboro end, the interchange is designed with I-40 as the exit. This is because they had intended that I-40 would continue with I-85 to the interchange south of Greensboro, and the interchange where they split now, was intended as the exit for Business 40 & Business 85.
Either way, even with I-40 on the southern loop, I-85 still has the priority where I-73 / former I-40 exited off for the southwestern part of the loop.

On the eastern end of the I-40 / I-85 concurrency, I-40 also exits off with design favoring I-85 through traffic.

speaking of Greensboro, the I-73/840 duplex has 73's exit numbers, but at the northern split, I-73 uses exit 107, which is it's own mileage...
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 24, 2021, 09:05:58 AM
In Virginia I-64 loses twice with both I-81 and I-95.  It used to have no exit numbers in the state but the toll road in Richmond had sequential numbering from 1 to 17 at that time so only part of I-95 had numbers with a smaller part of I-64.

I-64 in Hampton once had a set counting up from the HRBT left over from when VA 168 was the sole route through Hampton.
Interestingly, I-64 loses in all of its concurrencies except with I-55 in MO, where I-55 exits off as exit 40B. I mentioned I-75 and I-77 in the op already, there’s also one with I-57 in IL that’s a rule 2 example in my guidelines, and there’s the 2 VA examples.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: cabiness42 on January 24, 2021, 09:15:54 AM
The 2009 MUTCD does not specify which interstate gets priority.

Quote from: 2009 MUTCD 2E.31 Paragraph 16
Where numbered routes overlap, continuity of interchange numbering shall be established for only one of the routes (see Figure 2E-21). If one of the routes is an Interstate and the other route is not an Interstate, the Interstate route shall maintain continuity of interchange numbering.

As for exceptions to the rules in your post, the first rule has a few:

1) I-465 gets priority over I-74 around Indianapolis
2) I-694 gets priority over I-94 north of Minneapolis.
3) I-294 gets priority over I-80 south of Chicago



I think it would be easier for a loop to take priority over a 2di that is concurrent for only part of the time. Would be confusing for a segment of the loop to suddenly have different exit numbers.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: US 89 on January 24, 2021, 09:17:31 AM
I thought that “lower number gets priority” was a rule written down someplace.

In any case it lends itself to what I think is the worst numbered concurrency: I-15 and I-90 in Butte, MT. I-90 is the dominant route at both ends of the concurrency, both in terms of traffic counts and interchange configuration...but the overlap uses I-15 exit numbering, and the spur into Butte is designated I-115.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 24, 2021, 09:54:02 AM
With I-35/I-70 (Alphabet loop) in Kansas City, anyone else count it as I-70 getting priority in the exit numbers despite that they’re both exit 2? For me, I do because I-70 enters the loop with the A suffix and goes in alphabetical order before leaving, while I-35 starts towards the end of the letters, and hops back to A when the concurrency with I-70 starts. The beginning and end points of the loop could’ve been marked at the SW corner to start I-35 at A, but it was chosen at the NW corner, to start I-70 at A. Think this is another example for my rule 4, since I-70 is longer in the state.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 24, 2021, 10:04:35 AM
I think it would be easier for a loop to take priority over a 2di that is concurrent for only part of the time. Would be confusing for a segment of the loop to suddenly have different exit numbers.
I guess it depends on the 3di. But in the case of I-694, I-640 and I-294, they’re unnecessary concurrencies with a 2di just to terminate at a specific route. Those can be truncated at where their individual segment ends.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: Caps81943 on January 24, 2021, 11:42:17 AM
I thought that “lower number gets priority” was a rule written down someplace.

In any case it lends itself to what I think is the worst numbered concurrency: I-15 and I-90 in Butte, MT. I-90 is the dominant route at both ends of the concurrency, both in terms of traffic counts and interchange configuration...but the overlap uses I-15 exit numbering, and the spur into Butte is designated I-115.

Holy cow that's an egregious flaunting of common sense, if you showed me that with no prior knowledge, I may have bet a thousand bucks that 90 gets the exit numbers and the spur.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 24, 2021, 11:49:51 AM
I thought that “lower number gets priority” was a rule written down someplace.

In any case it lends itself to what I think is the worst numbered concurrency: I-15 and I-90 in Butte, MT. I-90 is the dominant route at both ends of the concurrency, both in terms of traffic counts and interchange configuration...but the overlap uses I-15 exit numbering, and the spur into Butte is designated I-115.

Holy cow that's an egregious flaunting of common sense, if you showed me that with no prior knowledge, I may have bet a thousand bucks that 90 gets the exit numbers and the spur.
I would too. Literally everything in there points towards I-90 having the exit numbers
1) I-15 leaves the concurrency on a single lane trumpet on both sides, while I-90 is the through movement.
2) I-90 is a much longer route in the state than I-15 (554 mi vs 396 mi)
3) I-90 mileage during the concurrency is higher than I-15 (219-227 vs 121-129)
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: Scott5114 on January 24, 2021, 12:11:04 PM
Thing is, if "lower number gets priority" were consistently followed, it would be common sense. It's much easier to figure out from the point of the concurrency which of two Interstates has a lower number. In some cases it can be hard to pick a "dominant route" or know which one is longer without looking it up.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: 1 on January 24, 2021, 12:19:23 PM
Thing is, if "lower number gets priority" were consistently followed, it would be common sense. It's much easier to figure out from the point of the concurrency which of two Interstates has a lower number. In some cases it can be hard to pick a "dominant route" or know which one is longer without looking it up.

81 is clearly dominant over 64.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: Scott5114 on January 24, 2021, 12:38:01 PM
81 is clearly dominant over 64.

So what? That isn't true for every Interstate concurrency. What's dominant between I-35 and I-80? They both have one concurrency terminus where one is the through route and one is the TOTSO. The concurrency is L-shaped, so you can't go off of which highway's alignment it follows. Traffic count? What, Joe Traveler is supposed to look up AADT maps to figure out how exit numbers work now? What if you're going through at midnight and you're the only car around so the dominant flow is non-obvious? Or the flow is equal between the two?

Every interstate concurrency is, however, guaranteed to have one route with a lower number than the others, which will be evident to the motorist without the need to refer to any outside sources. At least unless TxDOT starts multiplexing suffixed Interstates, that is.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: hobsini2 on January 24, 2021, 12:55:34 PM
The one that always made me shake my head is the 90-94 concurrency in Wisconsin between Tomah and Madison. That is clearly an example of your #4 rule. At Tomah, 94 is the main line. At Madison, it's 90. But they use I-90's numbers.  The only thing I can think for the reasoning is because of the lower number idea. 90 is roughly 187 miles in Wis vs 94 being roughly 348 miles.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: KCRoadFan on January 24, 2021, 01:02:14 PM
81 is clearly dominant over 64.

So what? That isn't true for every Interstate concurrency. What's dominant between I-35 and I-80? They both have one concurrency terminus where one is the through route and one is the TOTSO. The concurrency is L-shaped, so you can't go off of which highway's alignment it follows. Traffic count? What, Joe Traveler is supposed to look up AADT maps to figure out how exit numbers work now? What if you're going through at midnight and you're the only car around so the dominant flow is non-obvious? Or the flow is equal between the two?

Every interstate concurrency is, however, guaranteed to have one route with a lower number than the others, which will be evident to the motorist without the need to refer to any outside sources. At least unless TxDOT starts multiplexing suffixed Interstates, that is.

Between the two interchanges in Des Moines, the east-west distance is much greater than the north-south distance, so using I-80's mileage (as they do) makes sense there, in my opinion.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 24, 2021, 01:03:22 PM
81 is clearly dominant over 64.

So what? That isn't true for every Interstate concurrency. What's dominant between I-35 and I-80? They both have one concurrency terminus where one is the through route and one is the TOTSO. The concurrency is L-shaped, so you can't go off of which highway's alignment it follows. Traffic count? What, Joe Traveler is supposed to look up AADT maps to figure out how exit numbers work now? What if you're going through at midnight and you're the only car around so the dominant flow is non-obvious? Or the flow is equal between the two?

Every interstate concurrency is, however, guaranteed to have one route with a lower number than the others, which will be evident to the motorist without the need to refer to any outside sources. At least unless TxDOT starts multiplexing suffixed Interstates, that is.
The 2 examples for my rule 4 are L shaped concurrencies, where you can't tell which one is the dominant route. I thought the longer route in the state made sense, since that's what it seems like the most examples use. Besides I-57/I-70 and I-75/I-64, you mentioned I-80/I-35, which uses I-80's exit numbers. There's also I-55/I-72, which uses I-55's exit numbers

Another case is I-76/I-77 in Akron. I-76 exits off in a trumpet at one end of the concurrency, and I-77 exits off in a stack at the other end. The concurrency happens to use I-76's exit numbers even though I-77's mileage is larger at that point and is a longer route in the state than I-76. Maybe it's the lower number gets priority idea, but I think something else that gave I-76 the exit number priority is that the concurrency is entirely in the E-W direction, and I-76 is a E-W route.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: Revive 755 on January 24, 2021, 01:18:46 PM
The 2 examples for my rule 4 are L shaped concurrencies, where you can't tell which one is the dominant route. I thought the longer route in the state made sense, since that's what it seems like the most examples use. Besides I-57/I-70 and I-75/I-64, you mentioned I-80/I-35, which uses I-80's exit numbers. There's also I-55/I-72, which uses I-55's exit numbers

I-55 was around with those exit numbers many years before the I-72 designation was extended west to Quincy.

Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: TheGrassGuy on January 24, 2021, 01:56:07 PM
Pretty sure in real life it's whatever route was built first.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 24, 2021, 05:10:10 PM
Pretty sure in real life it's whatever route was built first.
There’s some states that would renumber exit numbers in a newly designated concurrency just to fit one of my 5 guidelines. Missouri is an example. The section of I-55 between I-44 and I-64 was originally I-55 only, and used I-55 exit numbers. After I-70 got rerouted and I-44 extended, this section’s exits got renumbered to follow I-44’s mileposts. Thought this made sense because I-55 leaves the concurrency on a 25 mph ramp to the PSB with I-44 as the through movement at the north/east end.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: I-55 on January 24, 2021, 06:49:58 PM
Pretty sure in real life it's whatever route was built first.
There’s some states that would renumber exit numbers in a newly designated concurrency just to fit one of my 5 guidelines. Missouri is an example. The section of I-55 between I-44 and I-64 was originally I-55 only, and used I-55 exit numbers. After I-70 got rerouted and I-44 extended, this section’s exits got renumbered to follow I-44’s mileposts. Thought this made sense because I-55 leaves the concurrency on a 25 mph ramp to the PSB with I-44 as the through movement at the north/east end.

Not that I-55 leaving on a 25 mph ramp is a unique circumstance or anything...
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: ran4sh on January 24, 2021, 07:56:54 PM
Pretty sure in real life it's whatever route was built first.
There’s some states that would renumber exit numbers in a newly designated concurrency just to fit one of my 5 guidelines. Missouri is an example. The section of I-55 between I-44 and I-64 was originally I-55 only, and used I-55 exit numbers. After I-70 got rerouted and I-44 extended, this section’s exits got renumbered to follow I-44’s mileposts. Thought this made sense because I-55 leaves the concurrency on a 25 mph ramp to the PSB with I-44 as the through movement at the north/east end.

Or because the section north of I-64 is I-44 only, they decided it made logical sense for the I-44 numbering to be continuous.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: hbelkins on January 24, 2021, 08:14:46 PM
The I-75/I-64 concurrency is interesting, because there's not very much difference between the mileage of the two in the state -- a mile or two at best.

I remember when the KY 1747 Hurstbourne Lane interchange was the easternmost Louisville exit with any significance. The Blankenbaker exit hadn't yet been built, and the Jefferson Freeway (KY 841, now Gene Snyder Freeway with I-265 added) extended only between US 60 and KY 155. There was an "Ashland 180" mileage sign just east of the Hurstbourne interchange.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 25, 2021, 11:40:32 AM
The I-75/I-64 concurrency is interesting, because there's not very much difference between the mileage of the two in the state -- a mile or two at best.
The in-state distance for those two are very close. Both have an exit 191, and I-75 also have an exit 192 in the 191 milepost, but I-64's exit 191 seems to be farther from the border than I-75's exit 191. I thought I-64 was a bit longer than I-75 for a while because of that, but it turns out that I-75 is 0.7 miles longer than I-64.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: PurdueBill on January 25, 2021, 11:46:37 AM
I thought that “lower number gets priority” was a rule written down someplace.

In any case it lends itself to what I think is the worst numbered concurrency: I-15 and I-90 in Butte, MT. I-90 is the dominant route at both ends of the concurrency, both in terms of traffic counts and interchange configuration...but the overlap uses I-15 exit numbering, and the spur into Butte is designated I-115.

Holy cow that's an egregious flaunting of common sense, if you showed me that with no prior knowledge, I may have bet a thousand bucks that 90 gets the exit numbers and the spur.
I would too. Literally everything in there points towards I-90 having the exit numbers
1) I-15 leaves the concurrency on a single lane trumpet on both sides, while I-90 is the through movement.
2) I-90 is a much longer route in the state than I-15 (554 mi vs 396 mi)
3) I-90 mileage during the concurrency is higher than I-15 (219-227 vs 121-129)

The worst part of the I-90/I-15 boobery is that in both directions of the breakup, it is signed as an exit to stay on I-15, using the I-15 exit number, which makes absolutely no sense.  It should either have I-90 as the "exit" (even though 15 is taking the 1-lane trumpet ramp and 90 is 2 lanes straight), or display no number (ala I-76 WB and I-77 NB in Akron), but not have what it has.  It's evidence that they know 15 is the exit really.

15 sags south as it heads NB in order to hitch onto 90, showing that 90 is the boss in the pair.  Seems like engineering judgement would be appropriate vs. a fixed rule of lowest number wins.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: ethanhopkin14 on January 25, 2021, 01:57:07 PM
Texas' two interstate concurrencies are both in San Antonio and are both with I-35, and both use I-35 mileage.  The I-35/I-410 makes since because I-35 shouldn't be using I-410's exists in the 30s over I-35's in the 160s, but the I-10/I-35 concurrency, I always thought I-10 should get the mileage since it was the more dominate route.  The reason I-35 gets the numbering is because I-10 is clearly running on I-35's roadway and not the other way around. 
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: sprjus4 on January 25, 2021, 02:41:44 PM
^

I-35 seems to make the most sense given it's the continuous route. I-10 is clearly using its roadway to connect to the other segment of I-10 northwest of Downtown.

I-37 / I-69E would be the next interstate concurrency, which it seems like I-37 would logically keep its exit numbers given it was first, and that I-69E is clearly running on its roadway, not the other way around.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: frankenroad on January 25, 2021, 03:08:10 PM
I'm not sure if there's already a guideline for exit number priority in interstate-interstate concurrencies in the MUTCD, but I'm guessing there isn't from all the inconsistencies I found in various examples around the country. I decided to create my own unofficial guidelines that makes the most sense to me, and is what I use in my fictional exit lists.

1) In concurrencies with a 2di and 3di, the 2di would have exit number priority: Examples: I-74 with I-275, I-95 with I-495, I-29 with I-435.
2) In concurrencies where one route clearly exits off at both ends of the concurrency, the through route would have exit number priority. Examples: I-75 with I-71, I-70 with I-71, I-76 with I-70, I-15 with I-80.
3) In concurrencies where one route clearly exits off on one end, but the other end isn't clear on which route looks like the exit because of lane count, angle of exit, left side placement, etc, the through route through the definite exit would have exit number priority. Examples: I-65 with I-70, I-75 with I-85, I-77 with I-64.
4) In concurrencies where one route exits off at one point, and the other exits off at the other point, the longer route in the state would have exit number priority. Examples: I-57 with I-70, I-75 with I-64. This is what I went off with in a fictional idea that involves an I-70 and I-95 concurrency (https://www.aaroads.com/forum/index.php?topic=28310.msg2563647#msg2563647).
5) In concurrencies where the exiting route can't be determined because of lane count, angle of exit, left side placement, etc, on both ends, the longer route in the state would have exit number priority.

Of course there are a couple of "rule breakers" examples around, like the I-90/I-94 concurrency in IL should be using I-90's exit numbers based on my guidelines. Part of the rule breakers are for historical reasons, like in the I-40/I-85 concurrency, that route was solely I-85 when it was first designated, and I-40 was added on later.

Would be interesting to see if anyone else have their own guidelines of sorts for exit number priority in interstate-interstate concurrencies, or any other exceptions to my guidelines.

I believe, in most cases, that a route number ending in 0 or 5 trumps routes ending in 1,2,3,4,6,7,8, or 9.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: SkyPesos on January 26, 2021, 12:55:33 PM
I believe, in most cases, that a route number ending in 0 or 5 trumps routes ending in 1,2,3,4,6,7,8, or 9.
Probably depends on the situation. Some examples of another digit over an x0/x5 are obvious why, like I-76 over I-70 in PA. I-59 over I-20 in MS was mentioned earlier in the thread. Illinois is the worst offender if x0 or x5 exit numbers should take priority over the other digits, with I-57 over I-70 and I-94 over I-90. I already mentioned why I-90 should have exit number priority over I-94 in the op, and the I-57 over I-70 makes sense, with the former route having higher exit numbers in the state.

And then there's another situation that is interesting; toll road mileage over an interstate's mileage. I know why the NY Thruway does it; to not have duplicated exit numbers on the toll road. But for some other examples, like the Kansas turnpike over I-70's, why? I don't think the Kansas Turnpike would have exit numbers between 366 and 410 by itself, so duplication is not a reason for the turnpike.
Title: Re: Exit number priority in interstate-interstate concurrencies
Post by: kphoger on January 26, 2021, 02:03:48 PM
And then there's another situation that is interesting; toll road mileage over an interstate's mileage. I know why the NY Thruway does it; to not have duplicated exit numbers on the toll road. But for some other examples, like the Kansas turnpike over I-70's, why? I don't think the Kansas Turnpike would have exit numbers between 366 and 410 by itself, so duplication is not a reason for the turnpike.

That's because you see the Turnpike as something that overlays I-70.  If you saw I-70 as something that overlays the Turnpike, then your opinion might be different.