3 Digit Interstates

[Mapmikey]

Why is it that NC is compelled to change their 3 di numbering scheme but when GA and SC finish a loop I-520 they do not change the numbering?

Ask I-640.  oh wait...it's still I-540.

NC did have at least two 3dis that were rejected as a 1xx designation and were later approved as 2xx (though the number itself was not the reason for the rejections).  587 was first proposed as 595 as a hedge against the segment west of 95 not being a part of the interstate system.

Otherwise I am not seeing any instances of NC changing its 3di system in the manner you describe.

[thspfc]

Well, obviously lower numbers have priority because there are a lot more 1xx and 2xx Interstates than 9xx and 8xx.

[tq-07fan]

In Ohio most of the 3DI's are numbered in order that they were commissioned.

I-70 I-270 was first in Columbus in the 1960's, I-470 around Wheeling 1970's, I-670, also in Columbus but not until 1995.

I-71 I-271 Cleveland way before I-471 between Cincinnati and KY in 1981.

I-75 I-275 was first in Cincinnati 1962. I-475 in Toledo shows being opened in the late 1960's. I-675 started building from I-70 south to OH 444 in Fairborn (I can't remember what that small portions were signed for) then onto WPAFB. I-675 continued south in the 1980's to reach I-75 so long after I-475 was in service.

I-80 I-280 Toledo 1959, I-480 Cleveland 1970's, I-680 Youngstown shows the 1960's though.

I-290 was cancelled but they never reused the number.

BTW I-675 is my favorite 3DI since I remember it being built. My dad and I would go out and clinch each new section as they announced it on the TV or radio.

Jim

[SkyPesos]

In Ohio most of the 3DI's are numbered in order that they were commissioned.

I-70 I-270 was first in Columbus in the 1960's, I-470 around Wheeling 1970's, I-670, also in Columbus but not until 1995.

I-71 I-271 Cleveland way before I-471 between Cincinnati and KY in 1981.

I-75 I-275 was first in Cincinnati 1962. I-475 in Toledo shows being opened in the late 1960's. I-675 started building from I-70 south to OH 444 in Fairborn (I can't remember what that small portions were signed for) then onto WPAFB. I-675 continued south in the 1980's to reach I-75 so long after I-475 was in service.

I-80 I-280 Toledo 1959, I-480 Cleveland 1970's, I-680 Youngstown shows the 1960's though.

I-290 was cancelled but they never reused the number.

BTW I-675 is my favorite 3DI since I remember it being built. My dad and I would go out and clinch each new section as they announced it on the TV or radio.

Jim

Something else interesting about Ohio's; no odd first digit has been used yet. Not that there's any road for an odd first digit, as all of our 3di form a part or is a loop or bypass, except maybe I-670. If I-670 was in some other states, for example, Missouri, it would be signed with an odd first digit.

[SkyPesos]

For x0 and x5 interstates (except 30 and 45), what are some common first digits for a 3di that some of those interstates lack? 5 is pretty common for an odd first digit, except I-70 doesn't have a I-570. Same with no I-455 for I-55. Also, I-55 have more odd first digit 3di than even ones (4 compared to 1), which is unusual, as the numbering system normally lends out more even first digit 3di.

[tq-07fan]

Something else interesting about Ohio's; no odd first digit has been used yet. Not that there's any road for an odd first digit, as all of our 3di form a part or is a loop or bypass, except maybe I-670. If I-670 was in some other states, for example, Missouri, it would be signed with an odd first digit.

I-670 really would be a good first candidate for Ohio's first Spur route 3DI. Run it as it is across to I-270 then concurrent with I-270 to OH SR 161 then across 161 to Newark.

Jim

[hotdogPi]

Ohio has some spur freeways (US 24 near Toledo, US 33 on both sides of Columbus, 4, 16/161, 59, arguably 129) and medium-distance connectors (2, 8, 11); they're just not Interstates.

[SkyPesos]

Ohio has some spur freeways (US 24 near Toledo, US 33 on both sides of Columbus, 4, 16/161, 59, arguably 129) and medium-distance connectors (2, 8, 11); they're just not Interstates.

Sry, meant to say “any existing 3di”, not “any road” in my post above.  I had the state’s non-interstate spur freeways in mind, except that the state isn’t interested in new interstates, so they will stay as state routes for a long time.

[kphoger]

I-55 have more odd first digit 3di than even ones (4 compared to 1), which is unusual, as the numbering system normally lends out more even first digit 3di.

Odd = spur
Even = loop/bypass

[ilpt4u]

I-55 have more odd first digit 3di than even ones (4 compared to 1), which is unusual, as the numbering system normally lends out more even first digit 3di.

Odd = spur
Even = loop/bypass

I-55's issues with Evens vs Odds 3dis is partially due to IL's views on when an Odd vs Even is appropriate

What became I-355 had early maps printed with the route named I-455, and it could easily have been given an Even/455

IL's I-155 could easily also be an Even, based on how other states apply the Even vs Odd rules, since it connects I-55 to I-74/Lincoln to Morton vs going out of the way to Bloomington/Normal to make that connection

MO/TN's I-155 could also qualify for an Even-ing once/if I-69 is constructed to I-40 in Memphis

AR's I-555 makes a great start to a fictional I-22 westward extension, but let Arkansas get caught up with I-49 and I-57 (maybe someday I-69) before we throw another Interstate Extension in their lap

I-255 is a bit "odd" anyway, since it forms a beltway together with I-270 around St Louis. Similar to I-494/694 for the Twin Cities, I guess. One could argue (most of) the route should have a unified designation, and give the short segment of I-270 between the IL I-255/I-270/IL 255 interchange and the I-55/I-70/I-270 interchange the Indy I-865 treatment

[SkyPesos]

I-255 is a bit "odd" anyway, since it forms a beltway together with I-270 around St Louis. Similar to I-494/694 for the Twin Cities, I guess. One could argue (most of) the route should have a unified designation, and give the short segment of I-270 between the IL I-255/I-270/IL 255 interchange and the I-55/I-70/I-270 interchange the Indy I-865 treatment

St. Louis's beltway has an interesting history regarding the number. MoDOT wanted I-144 for the section between I-55 and I-70 (exits 1-20), but got I-244 instead because it forms part of a beltway. The section between MO exit 20 and IL exit 15 was always I-270. Then, there was a proposal to number the entire beltway as I-270, with an I-870 at the northeastern corner or else it would've intersected itself. That was dropped and we got the 270/255 split, with the former 244 segment part of 270.

[SkyPesos]

Since this seems to be the general thread about 3 digit interstates now, here's something I have made up: the 3di frequency rate. Find a 2di route, and count every 3di occurrence of its own. Duplicated numbers will be counted separately from each other. Take the final total, and divide it from its parent route's length. This will give you what I call the "3di frequency rate". A number of 0 means that the 2di has no 3di. Besides 0s, let's see which 2di has the lowest 3di frequency rate, and which has the highest.

Example for I-75:
Length: 1786.47 mi
3di of I-75: I-175, I-275 x4, I-375 x2, I-475 x3, I-575, I-675 x3 = 14
1786.47/14 = 127.605 mi/3di

For the highest, I imagine I-25 would be the winner
For the lowest, some candidates I have in mind just from a glimpse are I-76 Eastern, I-78, I-85, I-91 and I-95. Someone else can feel free to calculate the number for them.

[thspfc]

Since this seems to be the general thread about 3 digit interstates now, here's something I have made up: the 3di frequency rate. Find a 2di route, and count every 3di occurrence of its own. Duplicated numbers will be counted separately from each other. Take the final total, and divide it from its parent route's length. This will give you what I call the "3di frequency rate". A number of 0 means that the 2di has no 3di. Besides 0s, let's see which 2di has the lowest 3di frequency rate, and which has the highest.

Example for I-75:
Length: 1786.47 mi
3di of I-75: I-175, I-275 x4, I-375 x2, I-475 x3, I-575, I-675 x3 = 14
1786.47/14 = 127.605 mi/3di

For the highest, I imagine I-25 would be the winner
For the lowest, some candidates I have in mind just from a glimpse are I-76 Eastern, I-78, I-85, I-91 and I-95. Someone else can feel free to calculate the number for them.

I-83 is the winner, by two miles over I-76.

[SkyPesos]

I made a spreadsheet with the number of signed current 3di today, here's some interesting facts I gathered from that spreadsheet:

- 40 2di numbers have a signed 3di. If including unsigned, the number goes up to 42, adding in I-24 and I-45.
- This shouldn't come as a surprise, but I-95 have the most signed 3di variants, at 30 of them, with I-80 (22), I-90 (15), I-75 (14), I-40 (13) and I-10 (13) behind it, as the 5 highest.
- The most used 3di first digit and with the most 3di variants are the I-2xx, with 29 of the 40 2di with an I-2xx, and 61 I-2xx variants.
- As expected, the I-1xx are the most used odd 3di first digit. For second place, 3xx have more total variants, but more 2di have a 5xx.

[Roadgeekteen]

I-540 is a stain upon humanity and should be renumbered instantly.

[SkyPesos]

I-540 is a stain upon humanity and should be renumbered instantly.

I-540 is not the only odd first digit that meets its parent interstate twice. See I-376 and I-520.

[Roadgeekteen]

I-540 is a stain upon humanity and should be renumbered instantly.

I-540 is not the only odd first digit that meets its parent interstate twice. See I-376 and I-520.

They are also bad.

[bugo]

I thin it is mostly random or there are state highways with the same number already present.  Arkansas seems to have an AR 340, AR 355, so that could partially explain why they went/are going with I-540 and I-555 over I-340 and I-355.  But there's no AR 330, so I don't see why it's I-530 instead of I-330.  I it is this general reason why Topeka has I-470 over I-270 since US 270 barely enters the state (are there any other places where a state could have a 3-digit interstate with the same number as  a 3-digit US Route?).

AR 340 wasn't commissioned until 1965. In 1958, AR 130 was renamed to AR 330, AR 30 was renamed to AR 130, AR 40 was renamed to AR 140 and AR 55 was renamed to AR 355, so these numbers could be used for the upcoming Interstates. So that means that 140, 340, 540, 740 and 940 were all unused at the time the interstates were numbered and they went with 540. As for I-30's numbers, 130 was in use at the time, but was renumbered to 330 anyway, so both of those numbers were available. AR 230 was commissioned in 1957, likely while Interstate numbering was still being worked on, and it would have been available. That leaves 430. 530. 630. 730. 830 and 930. I-555 was likely not named I-155 because of the close proximity to I-155 in Missouri and 355 conflicted with old AR 55. So some of these numbers were indeed open, and Arkansas renumbered several state highways so they wouldn't duplicate an Interstate number with a state number. Now that is all shot to hell with I/AR 440, I/AR 530 and I/US 49 all within the state. And that doesn't include I/AR 540, which existed in the 1990s. AR 57 will likely be renumbered soon, and AR 69 might be in trouble too.