I know the general rule of the first digit. Even goes around or through city and returns to its parent route. Odd spurs into a city never returning to its parent. Is there a standard which determines what the first digit will be?
Example,
Lets say we want an interstate to branch off I-40 and spur into a city and not return to I-40. Naturally the number will be either 140, 340, 540, 740, or 940. How is the first digit chosen?
I think it's fairly random.
That's what I was thinking. Although I've noticed that 2, and 5, are used a lot.
In the early days of the Interstate system, the numbers were chosen from 1xx or 2xx upwards. But as the planners grew to understand how they wanted to use odds and even numbers, they had to make changes. In New York for instance, the reason why there is a I-587 and I-787 and no I-387 or I-187, is because they used I-187 and I-387 for NYC area routes before renumbering them into even routes. They didn't renumber the others for whatever reason, so you have the I-5xx and 7xx.
Stephen Summers did quite a bit of research on this in the early 2000s for his former homestead website. Included were scans of the original planning maps that were used to come up with the original 3dis for many states. That is where I saw the x87 situation and also the x90's for NY too.
Depends on what's available. There's a 240 in Oklahoma already, so if ODOT wanted to establish a new x40 Interstate, they couldn't use 240 again. Similarly if they wanted to do a spur off of I-40 around Sallisaw and call it I-540, they'd probably get shot down by AASHTO because of the possibility of confusion with I-540 in Arkansas. Other than that, AASHTO would probably accept whatever the DOT submitted in their application for an interstate route number. Texas got an I-820 even though there are no other x20s in the state.
Generaly when the state applies for a 3di designation they first have to get the route itself. i.e. point a to point b approved by the FHWA using the number the state would like to use. Then, after the route addition has been approved, AASHTO would either approve it or advise a new number to use. Usually from all the instances i've seen AASHTO approves the state requested number.
So, lets use an example:
On the 11-10-1958 AASHO approved the Phoenix spur of I-510 into Phoenix starting at I-10 & 7th Street North via 7th Street ending at Van Buren Street.
Then, on the 6-24-1969 Arizona extended I-510 Northward and Westward to the present intersection of I-10/I-17 on the West side of Phoenix and change its designation to I-410. AASHO approved this change.
Then, the BPR requested that I-410 should be changed to I-10 and extend I-17 South and East to the relocated I-10 on the South side of Phoenix. AASHO, BPR and AZ concured on the 11-17-1969.
This is kind of a rudementary example of what I think you are looking for.
Take Care,
Stephen Summers
Even though VA 895 is not an interstate(it definitely should be) they chose 895 over 695 as there was already an SR 695 even though neither Chesterfield nor Henrico Counties(which doesn't have SRs) use 895. I'm assuming that could be part of the reason for future I-785 in the Danville area.
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?).
I've been told that some states don't like to use I-1xx since "1" is sometimes confused with "I-".
Quote from: 74/171FAN on March 27, 2009, 01:14:06 PM
Even though VA 895 is not an interstate(it definitely should be) they chose 895 over 695 as there was already an SR 695 even though neither Chesterfield nor Henrico Counties(which doesn't have SRs) use 895. I'm assuming that could be part of the reason for future I-785 in the Danville area.
Well, there's I-664 in Suffolk, though Suffolk doesn't have a SR 664 (662 and 666, but no 664).
VA 785 (future I-785, which is on US 29 in Danville) enters Pittsylvania County, which has a SR 785. If VA 785 becomes I-785, then 785 would indeed duplicate in that area.
QuoteI 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.
Revive, I must humbly beg to differ with you. There IS an AR 330, in Van Buren County, according the Arkansas State Highway and Transportation Department. There are two sections of it, actually.
Also, in the near future, there will be an I-130 in Arkansas, which will replace AR 245 on the east side of Texarkana. I-130 will be a predecessor to I-49, if and when it reaches southwest Arkansas from Louisiana.
My guess is that numbers will increase from west to east, or north to south, much like the parent routes (the obvious exception being I-238 in California). Note: the rule would apply to 3-digits from the same parent route.
For example, (hidden) I-110 in El Paso is west of I-410 in San Antonio, which is west of I-610 in Houston.
QuoteMy guess is that numbers will increase from west to east, or north to south, much like the parent routes (the obvious exception being I-238 in California). Note: the rule would apply to 3-digits from the same parent route.
For example, (hidden) I-110 in El Paso is west of I-410 in San Antonio, which is west of I-610 in Houston.
Theory works, including dead routes or numbers, but excluding future routes:
* AL: this state may be the best example of leaving space for future spurs in this number scheme.
- I-59
- I-65
* CO (with I-425 once considered for I-270)
* IL
- I-55
- I-74, since the preliminary numbering around Quad Cites had an I-274
* IN
- I-65
* KS
- Both I-35 and I-70
* MI
- I-75
- I-96
* MO
- I-55 (assuming MO 755 was going to eventually be promoted from state route to interstate)
* MT
- I-15
* LA
- I-10
* OH
- I-80
* SC
- I-26
- I-85
* TN
- I-40 (if I-840 came that much later than I-640)
* TX
- I-10
- I-35? I-635 at Dallas allows for future routes in San Antonio and Austin
* VA
- I-81
Theory doesn't work
* IL
- I-70 (I-870 once considered for I-270 between I-255 and I-55/I-70)
* MO
- I-70 (I-670 would be I-270, I-270 would be I-670)
* NE
- I-80 (swap I-480 and I-680; given the attempts at spurs to Grand Island and Hastings, I-180 should have a higher first digit)
* OH
- I-70 (I-470 should be in Columbus, I-670 at Wheeling)
- I-71 (swap I-271 and I-471)
- I-75 (I-475 at Dayton, I-675 at Toledo
I'm probably missing a few on both sides, plus the added complications of multi-state routes
In the not category:
PA
- I-76 (I-176 east, I-276, Philly, I-376 Pittsburgh, I-476 Philly to Scranton, future I-576 Pittsburgh, I-676 Philly)
- I-79 (has I-279 and I-579 and nothing else)
- I-80 (seems to fit but 180 was designated after 380)
As for TN:
Well 840 is still a state route for now. And the evens are OK (240 Memphis, 440 Nashville, 640 Knoxville), but you have I-140 near Knoxville.
timhomer2009 wrote:
My guess is that numbers will increase from west to east, or north to south, much like the parent routes (the obvious exception being I-238 in California). Note: the rule would apply to 3-digits from the same parent route.
For example, (hidden) I-110 in El Paso is west of I-410 in San Antonio, which is west of I-610 in Houston.
I never thought of it that way (though I probably should have, doh!). But that makes the most sense. Yes there are exceptions but that will always happen.
Former I-510 in Phoenix which is west of once proposed I-710 in Tucson. That rule applies here.
Thanks for the examples too Revive 755.
I-90 in WA has no auxiliary routes for its 300 mi in WA...
Trying to see if this applies to California..
I-80:
I-280, I-380 (east of I-280), I-480 (was east of the original I-280 proposal in SF), I-580 (though I think that got its number as a result of formerly being I-5W - not the only time a previous designation led to the current number), I-680...
I-780, I-880, and I-980 all came later and don't fit.
I-5 definitely doesn't work to this scheme:
I-105 (both the current second incarnation of the route, and the 1960s version along US 101 in downtown Los Angeles) was always hundreds of miles south of I-205.
I-10 strangely fits, with I-710 being east of I-110 (but still being an unusually large number in the sequence, that derived from the previous designation of Route 7).
Quote from: Greybear on March 28, 2009, 03:20:09 AM
QuoteI 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.
Revive, I must humbly beg to differ with you. There IS an AR 330, in Van Buren County, according the Arkansas State Highway and Transportation Department. There are two sections of it, actually.
Also, in the near future, there will be an I-130 in Arkansas, which will replace AR 245 on the east side of Texarkana. I-130 will be a predecessor to I-49, if and when it reaches southwest Arkansas from Louisiana.
There's also an AR 130, which runs through east central Arkansas. Part of what is now US 165 was once AR 130. It was originally AR 30, which was renumbered when I-30 came along.
Speaking of AR 355, it was also renamed because of the interstate system, as it was originally AR 55. Also, what was once AR 40 is now AR 140.
*QUOTE* Scott5114 said: Texas got an I-820 even though there are no other x20s in the state. *END QUOTE*
I thought that was mainly due to the influence of one of the Dallas radio stations, 820 AM.
QuoteIn New York for instance, the reason why there is a I-587 and I-787 and no I-387 or I-187, is because they used I-187 and I-387 for NYC area routes before renumbering them into even routes.
All the 3dis in metro NYC are first digit even. Whether it makes sense for them to be or not:
278 (sort of), 478 (no), 678 (no), 878 (no), 280 (yes), 684 (arguably), 287 (yes), 295 (no), 495 (definitely no), 695 (yes), 895 (yes)
...of course, the x78's are a huge chunk of weirdness in and of themselves. Not orphaned, but abandoned.
QuoteAll the 3dis in metro NYC are first digit even. Whether it makes sense for them to be or not:
278 (sort of), 478 (no), 678 (no), 878 (no), 280 (yes), 684 (arguably), 287 (yes), 295 (no), 495 (definitely no), 695 (yes), 895 (yes)
...of course, the x78's are a huge chunk of weirdness in and of themselves. Not orphaned, but abandoned.
What wrong with I-278 and I-295 since they do end at interstates at both ends?
I-278 ends at US 1/US 9 on its western end, not at another Interstate. Meanwhile, I-295 ends at NY 25/Hillside Ave, just south of Grand Central Pkwy. Again...not at another Interstate.
So by the book, both routes should be odd 3-digit routes. Though at the same time, they got their numbering because they were both intended to connect to other Interstates.
Another note on I-278: neither it nor I-478 connect to I-78.
QuoteI-278 ends at US 1/US 9 on its western end, not at another Interstate. Meanwhile, I-295 ends at NY 25/Hillside Ave, just south of Grand Central Pkwy. Again...not at another Interstate.
So by the book, both routes should be odd 3-digit routes. Though at the same time, they got their numbering because they were both intended to connect to other Interstates.
Another note on I-278: neither it nor I-478 connect to I-78
First these interchanges are close enough to other interstates that it's warranted(as the end is just afterward). I-678 and I-878 don't connect tp I-78 either BTW.
3DI's of I-90 in New York increase in numbering from west to east (except I-990):
Buffalo:
Rochester:
Syracuse:
Utica:
Albany:
QuoteI-295's south end is a mile-and-a-half and 2 full interchanges past I-495.
I got I-495 confused with the Grand Central Pkwy :banghead: :pan: The theory also works on I-85 in SC(I-185, I-385, and I-585(even though it doesn't currently begin at I-85).
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?
Quote from: Avalanchez71 on February 10, 2021, 07:31:00 AM
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.
Well, obviously lower numbers have priority because there are a lot more 1xx and 2xx Interstates than 9xx and 8xx.
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
Quote from: tq-07fan on February 10, 2021, 12:10:29 PM
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.
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.
Quote from: SkyPesos on February 10, 2021, 12:49:24 PM
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
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.
Quote from: 1 on February 10, 2021, 01:15:35 PM
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.
Quote from: SkyPesos on February 10, 2021, 12:57:26 PM
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
Quote from: kphoger on February 10, 2021, 01:39:36 PM
Quote from: SkyPesos on February 10, 2021, 12:57:26 PM
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
Quote from: ilpt4u on February 11, 2021, 01:06:44 PM
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.
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.
Quote from: SkyPesos on February 12, 2021, 11:50:04 PM
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.
I made a spreadsheet (https://docs.google.com/spreadsheets/d/1N68cWsgFSo14bsXzUOJpnpWcBlnPo622pRx2dhCLTso/edit?usp=sharing) 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.
I-540 is a stain upon humanity and should be renumbered instantly.
Quote from: Roadgeekteen on June 13, 2021, 11:48:30 AM
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.
Quote from: SkyPesos on June 13, 2021, 06:18:39 PM
Quote from: Roadgeekteen on June 13, 2021, 11:48:30 AM
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.
Quote from: Revive 755 on March 27, 2009, 04:18:39 PM
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.