Obviously even #'s are for loops/bypass that reconnect at a second point with the parent interstate while roads which do not reconnect to the parent and spur are odd numbers.
But:
1. How do they determine if a highway is 284, 484, or 684 all things being equal (such as no other route with that designation)?
2. If a highway starts at one interstate (like 95) and connects to another (like 64 hypothetically), is that considered a loop since it does connect to another interstate or a spur?
For question 2, there's several examples in California of even 3dis not terminating at its parent:
I-280 - never touches its parent (although it was planned to) - termini are I-680 and King Street
I-680 - termini are I-80 and I-280
I-880 - termini are I-80 and I-280
I-205 - termini are I-5 and I-580
I-605 - crosses I-5, but termini are I-210 and I-405
I-210 - termini are I-210 (in both the AAHSTO and the CA-210 versions) and I-5
Several of these (880, 205, 605) could perhaps more correctly be considered spurs. To me I-605 definitely feels like two spurs from I-5 rather than part of a bypass/loop.
For the first question, I'm not sure if there's a specific method traditionally used for determining the first digit, aside from maybe how important the area served by said highway is, but that's a completely wild guess of mine.
New York does it best with x-90 children minus I-990 which came later. From 1 to 8 there is an order with 1-2 starting in the west and 8 in the east.
Some could argue that 3 is east of 4 as I-490 spurs west of I-390 on their parent. However, it's close enough with I-490 extending east of I-390.
I created a spreadsheet regarding first digit vs. length. There is almost no correlation (and what does exist is the opposite of what you'd expect; lower numbers are just barely shorter).
I know I-287 in NY and NJ was supposed to be an x-95 as it should as both I-287 terminuses are at I-95 and not its parent. However, all the digits for an I-95 child were used ( or planned to have been) at the time of numbering.
Why I-684 in Westchester County, NY is not an odd Spur is unclear, but it connects two interstates so it doesn't violate the rules.
I-495 on Long Island should have been I-395 as it never was intended to be a loop nor will it ever be. It doesn't terminate at interstates either end presently. Originally I-495 was to spur from I-95 at Secaucus, NJ, but cancellation of the Mid Manhattan Expressway foiled that and NJ's portion became State Route 495. Its only connection to I-95 is via I-295 in Queens. Yes, I-278 too, but in terms of siblings I-295 makes it legit to be an x-95 designation.
Am of belief that a Long Island Sound crossing was envisioned, when the route #'s were being assigned, so that explains the 495 number on what is essentially an orphaned spur. Would have been interesting to have seen what would have played out, in terms of where the route would have landed in Connecticut on 95, had the crossing been built.
I know in Tennessee, the even-numbered I-40 children increase as you go from west to east (I-240 in Memphis, I-440 in Nashville, and I-640 in Knoxville), save for I-840 around Nashville, which was added later and likely got the number due to being available at the time. Dunno how much correlation location and first digit number have with each other in general though, I-140 and I-124 in Tennessee are both in the eastern part of the state (Knoxville and Chattanooga respectively), while I-265 used to exist in Nashville.
I always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
Quote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
Tell that to I-820
Generally speaking, I'd say it's somewhat dependent on location. The westernmost spur in the state might be 180, the easternmost might be 980. But this can fall apart unless all the envisioned spurs are built at the same time.
In some cases, numbers might try to fit into the state route network. Nevada, for example, likely gave 580 that number because "5xx" is used for state routes in urban areas. So it fit in quite well.
In other cases, it could simply be sequential. The first spur is 1xx, the second one 2xx, and there may not be any adherence to odd numbers being for spurs, even numbers being for loops, etc.
Basically, there are no real standards or rules, as none of those were truly established. Merely guidelines about how numbers should be used.
Quote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
x94, low by Chicago, mid in Minnesota, high by Milwaukee.
Quote from: jlam on April 02, 2024, 05:45:59 PMQuote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
Tell that to I-820
Wasn't that State Route 820, then they gave it an upgrade to I-820? I believe that's the backstory there as to how it was given an unusually high number.
I remember reading somewhere that 820 was used to advertise a local AM radio station.
In the case of Minnesota, the numbers are simply the lowest available numbers that aren't already in use by another state highway. I don't know why they chose to stick a 1 in front of former state highways 35 and 94 rather than, say, extending TH 200 over current TH 194 and choosing a completely different number for 135 in order to free up those numbers, but a nice benefit resulting from that is there was no duplication with 3-digit interstates other states. There would have been if 335 was built in Minneapolis and 494 was built in Chicago, though.
In Michigan, they go low to high from W to E (96) and from S to N (75). Same as mile markers.
California:
The original 1956-era designations were...
I-5: I-405, I-605, I-805
I-10: I-210
I-80: I-280, I-480, I-680
Then as the network expanded:
I-5: I-205 added ca. 1958-1959 (as a result of 5 being moved away from the 99 alignment in Modesto to the West Side alignment), I-505 (formerly planned as I-5W) added in 1964, as was the original I-105; current I-105 created in 1968. Unsigned I-305 along US 50/former I-80 created in 1982, Future I-905 designated in the early 1980s (so 705 has been skipped entirely)
I-10: Original I-110 designated in 1964 and rescinded several years later. Current I-110 created in 1981 (number derived from 1934-1981 Route 11), current I-710 designated in 1984 (number derived from 1964-1984 Route 7), which means that 310 and 510 were skipped.
I-15: I-15E became I-215 in 1982
I-80: I-580 created in 1964 on what had been I-5W/US 50, original I-880 designated in 1964 for the North Beltline in Sacramento, then removed in 1982; I-380 designated ca. 1970, I-780 created from old I-680 alignment in 1976, I-980 designated on what had been planned as Route 24 ca. 1981; current I-880 created from a potion of Route 17 in 1984 (and then there's I-238...)
Essentially, California did number their 3dis somewhat geographically sequentially at first (note that 205 is way north of 405, which has a terminus slightly north of 605's path, and then that is pretty far north from 805), then just started filling in gaps afterwards.
Looking at the example of I-80: the original sequence was 280 as the westernmost (with 80's planned terminus at 280/1 in Golden Gate Park factored in), then 480 along the waterfront, 680 inland from San Jose to Concord to Vallejo. (The Sacramento 880 fit this sequence, and the road was planned in the late 1950s, but was not given the 3di number until the 1960s)
Quote from: jeffandnicole on April 02, 2024, 06:05:18 PMQuote from: jlam on April 02, 2024, 05:45:59 PMQuote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
Tell that to I-820
Wasn't that State Route 820, then they gave it an upgrade to I-820? I believe that's the backstory there as to how it was given an unusually high number.
I-820 was built from the old existing loops in Fort Worth: Loop 217 (Present Day I-20 near US-377) and Loop 820 (From I-35W south to SH-121). In addition, new sections of highway were built to complete the loop around Fort Worth (specifically in the Northwest quadrant)
On the topic of 3 di interstates, I think Fort Worth is a candidate for another 3di interstate loop around I-820.
Quote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
Wisconsin has I-894 and I-794. No other routes were planned.
Quote from: roadman65 on April 02, 2024, 04:13:38 PMI-495 on Long Island should have been I-395 as it never was intended to be a loop nor will it ever be. It doesn't terminate at interstates either end presently. Originally I-495 was to spur from I-95 at Secaucus, NJ, but cancellation of the Mid Manhattan Expressway foiled that and NJ's portion became State Route 495. Its only connection to I-95 is via I-295 in Queens. Yes, I-278 too, but in terms of siblings I-295 makes it legit to be an x-95 designation.
One could say that I-495 would have worked as a loop if the Manhattan section had gotten built - if the rest of current I-495 hadn't been built, you could complete the loop via I-295.
There are plenty of examples of states that went with the plan of numbering 3dis west to east and south to north. And plenty of states where they just went with whatever they felt like.
The Michigan, New York and Tennessee examples have been cited already as places where there was a "system" they were following.
It was clearly on the mind of planners when they picked 3di numbers for Milwaukee going with higher first digits since the city was so far east on I-94's path thru the state. Ostensibly, that holds lower numbers in some kind of "reserve" for future spurs and loops further west.
The progression of 185, 385, 585 in South Carolina is another example.
This is why Baltimore has all high numbered x95's while lower number x95's are around the Maryland side of DC.
Thinking about Texas in this context and its clear similar thinking was in place.
210 left open for a future loop in El Paso; 410 San Antonio, 610 Houston.
The main Dallas loop got 635 telegraphing the intent to potentially use 235 and 435 further south some day.
This insight explains why you see seeming outlier 3di numbers where they could have gone with a lower number but didn't. They were skipping some numbers so they could backfill later if needed and still be in sequence.
Alabama: 359 and 759 match up well to add a 559 to Birmingham.
Minnesota: Duluth gets 535 instead of a lower number because it's further north. (Tho the other factor there is explained by Molandfreak)
Georgia: 985 is a massive outlier until one considers it in the context of leaving 3, 5 and 7 available for future spurs in Atlanta.
One thing is certain, 1xx and 2xx are far more common 3di numbers than any other leading first digit indicating a default practice of starting at bottom and working your way up. (That's how we end up with two I-291's a stone's throw from each other.)
At least that's how it seems to have gone down when the first batches of 3dis were being assigned.
In recent decades, it's been more like whatever someone feels like, or based on some arbitrary in-state "rule" that isn't actually a rule, but likely the preference of a single individual at some point that everyone went along with.
Examples: Arkansas picked all 5xx's for their long spurs.
Oklahoma and their obsession with new 3xx's for their toll roads.
But every so often we get a throw back to an era where people thought about the future. The relatively new spur to Fort Drum in New York was given 781, conveniently leaving the door open for 3 other spurs further south to be in sequence. And now as NY plans on moving 81 onto 481 in Syracuse, roadgeeks be all like, "Make the new stubs 3dis!"
If they did, the system would suggest the north stub becomes 581 and the south stub becomes 381.
What instance were Texas did probably make a mistake with the designations is with interstate 345 in Dallas.
There are at least three potential spare routes that could be designated off I 45 south of Dallas.
In a perfect world, FM, 1764 in Texas City would be an IH-145, the NASa Parkway Freeway bypass would be IH-345, the Hardy toll road could be redone as IH-245 or IH-445 with the airport connector being an IH- 545
Quote from: roadman65 on April 02, 2024, 04:13:38 PMI-495 on Long Island should have been I-395 as it never was intended to be a loop nor will it ever be. It doesn't terminate at interstates either end presently. Originally I-495 was to spur from I-95 at Secaucus, NJ, but cancellation of the Mid Manhattan Expressway foiled that and NJ's portion became State Route 495. Its only connection to I-95 is via I-295 in Queens. Yes, I-278 too, but in terms of siblings I-295 makes it legit to be an x-95 designation.
It's worth noting that the original I-495 ended at I-295; east of there was NY 495.
A few other examples that came to mind:
Nevada: IIRC the usage of I-515 and I-580 (starting with their designations in the 1970s and eventual in-field signings in the 1990s and 2010s respectively) fits in with their state route highway numbering system for some reason.
Washington: Isn't I-705 derived from WA 7? Otherwise, straightforward geographic sequence (I-205, I-405).
Arizona: The Phoenix area had a proposed I-410 (briefly signed) and I-510 (which led to today's AZ 51) and proposed I-710 in Tucson, which means...lots of skipped numbers (110, 210, 310)
North Carolina: I-40's progression of 3dis was originally west to east: I-240 Asheville, I-440 Raleigh, planned I-640 (now I-540) as outer loop of Raleigh. I-840 in Greensboro is basically infill, not unlike the I-840 around Nashville
I-85 on the other hand...I-485 is the very first 3di upon entering the state, and I-285 is a much later designation near Winston-Salem, with I-885 used for the newer Durham connector with US 70 (and 685 being proposed for US 421). The first odd 3di on the list is...I-785.
Quote from: vdeane on April 03, 2024, 07:32:20 PMQuote from: roadman65 on April 02, 2024, 04:13:38 PMI-495 on Long Island should have been I-395 as it never was intended to be a loop nor will it ever be. It doesn't terminate at interstates either end presently. Originally I-495 was to spur from I-95 at Secaucus, NJ, but cancellation of the Mid Manhattan Expressway foiled that and NJ's portion became State Route 495. Its only connection to I-95 is via I-295 in Queens. Yes, I-278 too, but in terms of siblings I-295 makes it legit to be an x-95 designation.
It's worth noting that the original I-495 ended at I-295; east of there was NY 495.
Ugh...you're reminding me of the headache one has when determining which shielded Interstates in NYC are eligible.for 90% NHPP and which ones are not.
Quote from: TheStranger on April 03, 2024, 08:41:07 PMNevada: IIRC the usage of I-515 and I-580 (starting with their designations in the 1970s and eventual in-field signings in the 1990s and 2010s respectively) fits in with their state route highway numbering system for some reason.
Urban arterial routes in Nevada start with 5 or 6 and are allocated in blocks by county. Amusingly, though, 515 is a Carson number and 580 is a Clark County number. There's obviously no other way to comply with Interstate numbering, though.
This implies that if I-11 ever gets an auxiliary route in Southern Nevada, it will be I-611, since that's a Clark County number that currently isn't in use.
As for determining which odd or which even number to use, doesn't the state suggest a number and then either get it approved or denied? At least, that's how I think it works. In which case, it's whatever number someone thinks is a good idea at the time.
Quote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
I'm pretty sure that's how Ohio does it. I know that 275, 475, and 675 were constructed in that order; and I'm sure 271 is older than 471. 270 is the oldest of the x70s. In reviewing old maps, it looks like 470 was assigned a number before 670, even though some of what is now 670 was built first.
Quote from: frankenroad on April 05, 2024, 04:14:31 PMQuote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
I'm pretty sure that's how Ohio does it. I know that 275, 475, and 675 were constructed in that order; and I'm sure 271 is older than 471. 270 is the oldest of the x70s. In reviewing old maps, it looks like 470 was assigned a number before 670, even though some of what is now 670 was built first.
This seems to be how Florida has done it. I believe 110, 175, 375, 195, 295 and 395 were all part of the original plan for Florida interstates. After not too long came 275. Plans for 595 came later, and 795 later still.
Arkansas' 2dis and 3dis seem set, so ARDOT is using the midrange 4xx through 6xx state numbers as placeholders for future extensions of major roads. They've already used 3xx as replacement numbers for former US highways subsumed by parallel freeways (namely 365 and 367).
Quote from: SEWIGuy on April 03, 2024, 08:36:15 AMQuote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
Wisconsin has I-894 and I-794. No other routes were planned.
That is an interesting one. I always wondered if they skipped 294 because Illinois had already used it not too far south of the Milwaukee metro area.
MAYBE they thought of 394, 494 and 694 in Minnesota, but the Twin Cities are a long way from 894 and 794. Plus, it wouldn't explain why 194 and 594 were skipped.
One I don't understand is I-985 in Georgia. Obviously I-185 is already taken as a spur to Columbus, but I've always wondered why I-385 and I-585 were skipped. Maybe because of confusion with the ones already in South Carolina. If that's the case they also skipped I-785 which was open as well.
I mentioned before in a similar thread that an equally interesting question is how the "mainline" number part of a 3di is selected when the route has a terminus/termini at more than one. For example, I-359's southern terminus in Tuscaloosa AL is at the I-20/I-59 duplex. Was it a random pick between I-359 and I-320, or was there some rationale involved? Is it because I-359 is signed as north-south? Okay, then how about I-280 in Ohio, with a northern terminus at I-75 and a southern terminus at I-80/I-90? It's also signed north-south, so why not I-x75? If cardinal directions weren't an issue, why not I-x90?
Quote from: OCGuy81 on April 08, 2024, 08:33:43 AMMAYBE they thought of 394, 494 and 694 in Minnesota, but the Twin Cities are a long way from 894 and 794. Plus, it wouldn't explain why 194 and 594 were skipped.
Milwaukee is also the eastern part of the state, and towards the eastern end of I-94 in Wisconsin. I wouldn't be too surprised if they wanted to "save" the lower/skipped numbers for potential spurs and bypasses in the parts of the state to the west of Milwaukee.
Quote from: MATraveler128 on April 08, 2024, 02:14:35 PMOne I don't understand is I-985 in Georgia. Obviously I-185 is already taken as a spur to Columbus, but I've always wondered why I-385 and I-585 were skipped. Maybe because of confusion with the ones already in South Carolina. If that's the case they also skipped I-785 which was open as well.
I could potentially see I-785 being used for a spur from I-85 to Athens, over what's currently GA 316 and US 29. I could also see I-385 maybe having been saved for a potential Atlanta-area interstate (GA 400?), with I-585 being skipped to avoid potential confusion with I-575.
Michigan's go in in order by number or at least that's how it is. I-75 has starting from the south going north I-275, I-375, I-475 and I-675. I-69 doesn't have any, I-94 just has I-194 and I-96 has I-196, I-496 and I-696. I'm not counting I-296 which is unsigned and already has another route number for the entire route.
Quote from: kphoger on April 05, 2024, 03:53:26 PMAs for determining which odd or which even number to use, doesn't the state suggest a number and then either get it approved or denied? At least, that's how I think it works. In which case, it's whatever number someone thinks is a good idea at the time.
If memory serves ISTHA wanted I-455 for the North-South/now Veterans Memorial Tollway (and early under-construction maps were even printed with 455), but AASHTO approved I-355, feeling the route was more of a suburban spur of I-55 compared to a bypass/loop
Quote from: Molandfreak on April 02, 2024, 06:35:41 PMIn the case of Minnesota, the numbers are simply the lowest available numbers that aren't already in use by another state highway. I don't know why they chose to stick a 1 in front of former state highways 35 and 94 rather than, say, extending TH 200 over current TH 194 and choosing a completely different number for 135 in order to free up those numbers, but a nice benefit resulting from that is there was no duplication with 3-digit interstates other states. There would have been if 335 was built in Minneapolis and 494 was built in Chicago, though.
The designation change of TH 94 to modern TH 194 predated the creation of TH 200 by about 10 years. 200 didn't come along until about 1969.
I heard rumors that MO Route 370 is not I-370 because AASHTO rejected that number and wanted I-870 which Missouri disliked. So they kept it a state designation instead.
Don't know if that's true as it was on Wikipedia for the MO 370 article. As we know anyone can change an article on that and there was a user on here who seemed capable of changing facts on roads to fiction just to be a prick as he was a top contributor for Wiki at one time.
Some neo-expansionist examples in the current day that are amusing to think about how little (or how much) order was factored in:
- I-490 in Illinois, logical sequence after the existing I-290 even-numbered route.
- The once-proposed I-227 (now I-27W) through Midland, and proposed I-327 (now I-27N!) as part of the Ports to Plains Corridor project/I-27 extension
- I-269 in Memphis, logical sequence, but I recall this was proposed as I-669 years ago.
- For that matter, I-369 was designated first in Texas, then I-169 way further down the state. Example of the geographic numbering coming into play? For that matter, it's interesting Indiana went with I-469 for the Fort Wayne loop route with 269 still available over there.
- North Carolina's newly concocted I-777 as of this very week!!! when no other odd x77 route even exists at this present time.
Quote from: TheStranger on April 12, 2024, 12:41:14 PMSome neo-expansionist examples in the current day that are amusing to think about how little (or how much) order was factored in:
- I-490 in Illinois, logical sequence after the existing I-290 even-numbered route.
I-490 for the ORD Ring Tollway is a bit of a divergence from how Illinois has designated 3dis previously. Other 3dis in IL that only touch their parent once have all received odds, even when connecting 2 (or more) interstates: 155 connects 55 to 74; 355 connects 55 to 80, 88, and 290 directly and 90 indirectly. 490 will obviously only touch 90 once, tho will meet sibling IL 390 also
The previous IL evens all touch the parent twice (tho the second time may not be in Illinois): 255, 270, 280, 290, 294, 474
Quote from: ilpt4u on April 12, 2024, 01:10:33 PMQuote from: TheStranger on April 12, 2024, 12:41:14 PMSome neo-expansionist examples in the current day that are amusing to think about how little (or how much) order was factored in:
- I-490 in Illinois, logical sequence after the existing I-290 even-numbered route.
I-490 for the ORD Ring Tollway is a bit of a divergence from how Illinois has designated 3dis previously. Other 3dis in IL that only touch their parent once have all received odds, even when connecting 2 (or more) interstates: 155 connects 55 to 74; 355 connects 55 to 80, 88, and 290 directly and 90 indirectly. 490 will obviously only touch 90 once, tho will meet sibling IL 390 also
The previous IL evens all touch the parent twice (tho the second time may not be in Illinois): 255, 270, 280, 290, 294, 474
Earlier in the thread, someone mentioned that I-355 was originally proposed as I-455, then AASHTO essentially steered them towards the 355 designation. Maybe 490 would have been 590 (factoring in IL 390) in the 1980s, but got its number retained in AASHTO's current lassiez-faire environment?
I did notice that 274 was skipped with Peoria having 474.
Quote from: TheStranger on April 12, 2024, 01:21:47 PMQuote from: ilpt4u on April 12, 2024, 01:10:33 PMQuote from: TheStranger on April 12, 2024, 12:41:14 PMSome neo-expansionist examples in the current day that are amusing to think about how little (or how much) order was factored in:
- I-490 in Illinois, logical sequence after the existing I-290 even-numbered route.
I-490 for the ORD Ring Tollway is a bit of a divergence from how Illinois has designated 3dis previously. Other 3dis in IL that only touch their parent once have all received odds, even when connecting 2 (or more) interstates: 155 connects 55 to 74; 355 connects 55 to 80, 88, and 290 directly and 90 indirectly. 490 will obviously only touch 90 once, tho will meet sibling IL 390 also
The previous IL evens all touch the parent twice (tho the second time may not be in Illinois): 255, 270, 280, 290, 294, 474
Earlier in the thread, someone mentioned that I-355 was originally proposed as I-455, then AASHTO essentially steered them towards the 355 designation. Maybe 490 would have been 590 (factoring in IL 390) in the 1980s, but got its number retained in AASHTO's current lassiez-faire environment?
I did notice that 274 was skipped with Peoria having 474.
That was me on the 455/355 thing
274 had something proposed in the Quad Cities, if I remember. Maybe what became I-74 downtown?
How was I-555 picked in Arkansas? Better yet I-540? Does AR like the number 5?
Quote from: roadman65 on April 14, 2024, 02:03:26 PMHow was I-555 picked in Arkansas? Better yet I-540? Does AR like the number 5?
Looks like 155, 355, 140, and 340 were taken.
California's use of the x05 auxiliaries is interesting. 205 and 605 are spurs, not loops. Their placement also feels reversed, like 205 should have been in SoCal and 605 farther north. Then you have 105, 505, 905. Again, feels like 505 and 905 should have been swapped, but then it's also curious as to why 305 and 705 were skipped. 305 does exist unsigned, but I've never read any reasoning as to why 705 was never used.
I say "swapped" because it seems the general assumption within the state is numbers progress from west to east. You can see this with 280 and 680; 380 and 580. 780 and 880 don't quite fit but were slotted in later, although the short-lived 480 was west of both. Then in SoCal, you can see 110 west of 710, 405 generally west of 605, etc. 110 and 710 make sense because they were more or less conversions of the original CA-7 and CA-11, so the numbers kind of fit. But otherwise seems some of the outlier numbers like 905 were just sort of picked at random.
Quote from: jt4 on April 14, 2024, 05:32:35 PMQuote from: roadman65 on April 14, 2024, 02:03:26 PMHow was I-555 picked in Arkansas? Better yet I-540? Does AR like the number 5?
Looks like 155, 355, 140, and 340 were taken.
I-155 and I-355? Not in Arkansas.
Quote from: roadman65 on April 14, 2024, 06:48:09 PMQuote from: jt4 on April 14, 2024, 05:32:35 PMQuote from: roadman65 on April 14, 2024, 02:03:26 PMHow was I-555 picked in Arkansas? Better yet I-540? Does AR like the number 5?
Looks like 155, 355, 140, and 340 were taken.
I-155 and I-355? Not in Arkansas.
I-155 is nearby, going from the SEMO Bootheel into NW Tennessee, so I think that is a good enough reason to DQ 155, especially in NE Arkansas. 355? Yea, where is the nearest 355, other than Chicagoland?
Quote from: ilpt4u on April 14, 2024, 06:55:50 PM355? Yea, where is the nearest 355, other than Chicagoland?
Near Texarkana, as a state route.
Quote from: Quillz on April 14, 2024, 06:42:02 PMCalifornia's use of the x05 auxiliaries is interesting. 205 and 605 are spurs, not loops. Their placement also feels reversed, like 205 should have been in SoCal and 605 farther north. Then you have 105, 505, 905. Again, feels like 505 and 905 should have been swapped, but then it's also curious as to why 305 and 705 were skipped. 305 does exist unsigned, but I've never read any reasoning as to why 705 was never used.
I say "swapped" because it seems the general assumption within the state is numbers progress from west to east. You can see this with 280 and 680; 380 and 580. 780 and 880 don't quite fit but were slotted in later, although the short-lived 480 was west of both. Then in SoCal, you can see 110 west of 710, 405 generally west of 605, etc. 110 and 710 make sense because they were more or less conversions of the original CA-7 and CA-11, so the numbers kind of fit. But otherwise seems some of the outlier numbers like 905 were just sort of picked at random.
I mentioned it earlier in the thread, but the x05 placement seems to be very specifically north-to-south:
https://www.aaroads.com/forum/index.php?msg=2917313
205 (created after the 1958 reroute of I-5 away from Route 99) - Altamont to Tracy
405 (original) - Sylmar to Irvine
605 (original, but extended) - original extent was Seal Beach to El Monte, then designation extended to Duarte/Irwindale
805 (original) - San Diego bypass, Sorrento Valley to San Ysidro via Mission Valley
That might explain why 905 was used right at the border, rather than 705. Both 105s were/are in SoCal but designated after the 1960s began; 505 is likely derived from the formerly planned 5W designation (note that 580 was not numbered 180 (conflicted with CA 180) or 380 when 5W was de-designated) and 305 was the lowest number x05 available in 1982.
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For the x80s, the originally planned routes prior to 1964 progressed west to east:
280 would have been the westernmost, had the Route 1/19th Avenue bypass been built between Font Boulevard and Lake Street in San Francisco.
480 was next in the sequence and was originally planned to start at 280/101 in the Presidio. (The built portion eventually had a western terminus at Broadway and Battery)
680 directly began east of 280 in San Jose (originally at the modern 880/101 junction, and now at the stack interchange east of downtown)
880 was a Sacramento bypass (now I-80)
Interestingly, none of the odd numbered x80 designations existed or were planned pre-1964, since 580 was signed in the field was 5W 1962-1964.
That's kind of weird, because it seems interstates in general try to put lower numbers in the south and west, and doing it that way also would have kind of fit into the state highway grid, where there was an attempt to have lower numbers as you went west. I guess it fits how they did it, just feels like a reversal.
Although it's interesting that using 905 near the border was in spirit of the original 1934 numbering scheme, which often used larger numbers near the border. 94, 96, 98 were numbered that way. Original SR-95 followed that logic. So I can see it, that does make some sense.
1. So basically when choosing which even or odd 1st digit, there is no rule, things vary by state?
2. Why is the DC beltway 495 and the Baltimore 695?
3. If a 3 digit interstate ends at another interstate it must be even, correct, EVEN if that interstate is not an offshoot of 2 digit (Fictionally 387 starts at 87 and ends at 684)?
Quote from: jeffandnicole on April 02, 2024, 06:05:18 PMQuote from: jlam on April 02, 2024, 05:45:59 PMQuote from: jeffandnicole on April 02, 2024, 05:34:50 PMI always figured they just started at the lowest number (1xx or 2xx) then went up as more were added. Occasionally a number may be skipped - a planned route never occurred, or an adjoining state already had the low route number so they used the next one to avoid confusion.
Tell that to I-820
Wasn't that State Route 820, then they gave it an upgrade to I-820? I believe that's the backstory there as to how it was given an unusually high number.
There sure is because radio station WBAP is on AM 820.
Quote from: bluecountry on April 19, 2024, 07:53:53 PM1. So basically when choosing which even or odd 1st digit, there is no rule, things vary by state?
From what I've seen in the thread, this seems to be the case. Some use middle or higher numbers to leave room for lower numbers in the future sequence (i.e. California starting out with 405 and 605 and 805, before creating 205), others do it purely in order (the odd 3dis in South Carolina), and some definitely are more "this number is available, why not use it" (I-820 in Texas stands out, as does I-985 in Georgia).
Quote from: bluecountry on April 19, 2024, 07:53:53 PM2. Why is the DC beltway 495 and the Baltimore 695?
Could this be "Maryland numbering things in geographic order" - 295, 495 both in the DC area, 695 then a bit up north?
Quote from: bluecountry on April 19, 2024, 07:53:53 PM3. If a 3 digit interstate ends at another interstate it must be even, correct, EVEN if that interstate is not an offshoot of 2 digit (Fictionally 387 starts at 87 and ends at 684)?
Not necessarily (see I-355, the Kansas I-135, the under-construction I-369, I-505). Note that 135 and 505 replaced suffixed Interstate routes (35W and 5W).
Quote from: bluecountry on April 19, 2024, 07:53:53 PM1. So basically when choosing which even or odd 1st digit, there is no rule, things vary by state?
2. Why is the DC beltway 495 and the Baltimore 695?
3. If a 3 digit interstate ends at another interstate it must be even, correct, EVEN if that interstate is not an offshoot of 2 digit (Fictionally 387 starts at 87 and ends at 684)?
1) Yes.
2) Sometimes, there is little reason behind the numbering.
3) No.
On thing that's worth noting is that 3di numbers don't duplicate within a state, and I-495 exists in both MD and VA (and a tiny piece of DC). Thus, I-295 for Richmond, I-495 for DC, and I-695 for Baltimore was somewhat dictated by the fact that I-495 exists.
Quote from: vdeane on April 19, 2024, 10:43:00 PMOn thing that's worth noting is that 3di numbers don't duplicate within a state, and I-495 exists in both MD and VA (and a tiny piece of DC). Thus, I-295 for Richmond, I-495 for DC, and I-695 for Baltimore was somewhat dictated by the fact that I-495 exists.
DC/MD do have the I-295 along the Anacostia River (which connects to DC 295/MD 295/Baltimore-Washington Parkway as one long corridor).
Quote from: TheStranger on April 20, 2024, 02:30:48 PMQuote from: vdeane on April 19, 2024, 10:43:00 PMOn thing that's worth noting is that 3di numbers don't duplicate within a state, and I-495 exists in both MD and VA (and a tiny piece of DC). Thus, I-295 for Richmond, I-495 for DC, and I-695 for Baltimore was somewhat dictated by the fact that I-495 exists.
DC/MD do have the I-295 along the Anacostia River (which connects to DC 295/MD 295/Baltimore-Washington Parkway as one long corridor).
Which notably does not enter VA. Similarly, Baltimore has a short I-395 while VA and DC have a longer one. And I-195 will exist separately in all three jurisdictions (while DC will lose its I-695) if/when the I-395/I-695 renumbering happens.
Quote from: bluecountry on April 19, 2024, 07:53:53 PM1. So basically when choosing which even or odd 1st digit, there is no rule, things vary by state?
Even vs. odd for the first digit is typically determined by the use the route will serve, IIRC. Odd numbers indicate it's a spur (for example: I-565 in Alabama) while even numbers indicate it's a bypass (for example: I-840 in Tennessee) or a beltway (for example: I-285 in Georgia).
So if a road is going from say I-66 north to I-70, could it be either even or odd? Would it depend if the road ends at the interstates (starts at 66 ends at 70) or if it continues beyond one or both?
Quote from: bluecountry on June 19, 2024, 06:00:05 PMSo if a road is going from say I-66 north to I-70, could it be either even or odd? Would it depend if the road ends at the interstates (starts at 66 ends at 70) or if it continues beyond one or both?
It could be any number the State puts forward at AASHTO.
Quote from: Rothman on June 19, 2024, 10:06:21 PMQuote from: bluecountry on June 19, 2024, 06:00:05 PMSo if a road is going from say I-66 north to I-70, could it be either even or odd? Would it depend if the road ends at the interstates (starts at 66 ends at 70) or if it continues beyond one or both?
It could be any number the State puts forward at AASHTO.
Consider I-196 and I-696 in Michigan, I-355 in Illinois, and I-275 in Tennessee, all of which connect two Interstates with different numbers. I don't count I-390 in New York for these purposes because its southern end was not originally at an Interstate.
Quote from: 1995hoo on June 20, 2024, 11:40:14 AMConsider I-196 and I-696 in Michigan
It has been mentioned here several times before. I-196 was originally planned as a spur off I-96, going from Grand Rapids to Muskegon. It was decided that, when what is now I-196 hadn't yet been built, it made no sense to have a freeway change numbers on the east side of GR. So the GR to Muskegon portion was renumbered as I-96, and when the freeway from GR to Benton Harbor was eventually build in stages, I-196 was applied to it.
Ideally, the first available digit of a 3di within a state should start with a 1 (for spurs) or 2 (for bypass loops), but of course it does not work that way. Several factors come into play here, such as no duplication and/or the refusal to renumber an existing state route (such as CA).
Quote from: 1995hoo on June 20, 2024, 11:40:14 AMQuote from: Rothman on June 19, 2024, 10:06:21 PMQuote from: bluecountry on June 19, 2024, 06:00:05 PMSo if a road is going from say I-66 north to I-70, could it be either even or odd? Would it depend if the road ends at the interstates (starts at 66 ends at 70) or if it continues beyond one or both?
It could be any number the State puts forward at AASHTO.
Consider I-196 and I-696 in Michigan, I-355 in Illinois, and I-275 in Tennessee, all of which connect two Interstates with different numbers. I don't count I-390 in New York for these purposes because its southern end was not originally at an Interstate.
Ok...now what?
Missed this thread originally, but replying to this post:
Quote from: Scott5114 on April 04, 2024, 04:34:48 AMQuote from: TheStranger on April 03, 2024, 08:41:07 PMNevada: IIRC the usage of I-515 and I-580 (starting with their designations in the 1970s and eventual in-field signings in the 1990s and 2010s respectively) fits in with their state route highway numbering system for some reason.
Urban arterial routes in Nevada start with 5 or 6 and are allocated in blocks by county. Amusingly, though, 515 is a Carson number and 580 is a Clark County number. There's obviously no other way to comply with Interstate numbering, though.
This implies that if I-11 ever gets an auxiliary route in Southern Nevada, it will be I-611, since that's a Clark County number that currently isn't in use.
While Nevada's primary (100-400 series) and tertiary (700-800 series) routes are assigned in ascending order by alphabetical order of counties, the urban routes (500-600 series) were mostly assigned in order by
city alphabetically. This was a byproduct of the federal aid highway system numbering that was implemented during the 1976 renumbering, and included many non-state owned/maintained facilities in the numbering. The low 500's were a couple numbers assigned in Boulder City (also in Clark County), and then the 510's started in Carson City and 535 was assigned in Elko. Then come the bulk of Clark County's urban routes Las Vegas Valley routes semi-alphabetically—Henderson got E/W routes in the 560's, then E/W routes in Las Vegas (and North Las Vegas) were assigned in the beginning at the 570s in the north increasing southward into the 590's in unincorporated Clark County, then N/S routes generally from west to east (spanning multiple jurisdictions) from 595 to 612. Reno and Sparks got the 640s through 660s (numbers weren't nearly as orderly with these cities).
In the federal aid system, FAU 611 was likely assigned to some north-south minor arterial between Lamb Blvd & Nellis Blvd (Mountain Vista St in Henderson, IIRC). Since the federal aid system numbering was abandoned (1991?), NDOT has, thus far, to my knowledge, not reused any numbers from that system for any new state routes created since then—they've just added new numbers within the old scheme within the gaps left for expansion in 1976. Therefore, an I-11 auxiliary route numbered 611 seems unlikely.
Quote from: bluecountry on April 19, 2024, 07:53:53 PM3. If a 3 digit interstate ends at another interstate it must be even, correct, EVEN if that interstate is not an offshoot of 2 digit (Fictionally 387 starts at 87 and ends at 684)?
Depends on state and AASHTO's mood at the time of number assignment, as I don't see a consistent pattern (like why MO 370 get rejected for an interstate of that number while I-540 in NC was approved even though both routes serve as bypasses for their parent route). Though I think more odd 3di numbers should be used in that case because every state has 5 odd 3di for a 2di, but only 4 even 3di, so theoretically it's more common to run out of even 3di in a state than to run out of odds.
Quote from: SkyPesos on July 07, 2024, 02:20:26 AMQuote from: bluecountry on April 19, 2024, 07:53:53 PM3. If a 3 digit interstate ends at another interstate it must be even, correct, EVEN if that interstate is not an offshoot of 2 digit (Fictionally 387 starts at 87 and ends at 684)?
Depends on state and AASHTO's mood at the time of number assignment, as I don't see a consistent pattern (like why MO 370 get rejected for an interstate of that number while I-540 in NC was approved even though both routes serve as bypasses for their parent route). Though I think more odd 3di numbers should be used in that case because every state has 5 odd 3di for a 2di, but only 4 even 3di, so theoretically it's more common to run out of even 3di in a state than to run out of odds.
Ideally, odd 3dis for spurs or 3dis that end at a 2di on one end only.
Ideally, even 3dis for 3dis that connect one 2di to another. This would include, but not limited to, many bypasses and beltways.
I would also say that these should not be hard and fast rules, but guidelines. A roadway that is an even 3di since it connects a 2di to another 2di, but is later extended further on one side so that it now acts as a spur, should retain its even 2di and not be renumbered. I see no valid purpose for a renumbering and all the extra confusion and signage changes required.
Also, it seems like lower numbered 3dis: 1xx, 2xx get used more than higher numbered 3dis: 8xx, 9xx. Does not appear to be any rhyme or reason to it, other than perhaps wanting to assign the numbers in some sort of order.
Quote from: SkyPesos on July 07, 2024, 02:20:26 AMDepends on state and AASHTO's mood at the time of number assignment, as I don't see a consistent pattern (like why MO 370 get rejected for an interstate of that number while I-540 in NC was approved even though both routes serve as bypasses for their parent route). Though I think more odd 3di numbers should be used in that case because every state has 5 odd 3di for a 2di, but only 4 even 3di, so theoretically it's more common to run out of even 3di in a state than to run out of odds.
This is why I do no understand the rationale for keeping I-894 around Milwaukee. They say "the number communicates that it's a bypass of downtown", but that is far from universally true, even in the Midwest. A sign that says "Downtown Bypass - Follow [I-41] North to [I-94] West" would work better for that and reduce numbering clutter. Still, I can explain that until I'm blue in the face, but they won't budge, probably because I'm a "meddling northeasterner".
Quote from: mrsman on July 07, 2024, 10:27:00 AMAlso, it seems like lower numbered 3dis: 1xx, 2xx get used more than higher numbered 3dis: 8xx, 9xx. Does not appear to be any rhyme or reason to it, other than perhaps wanting to assign the numbers in some sort of order.
That is the rhyme and reason of it. They are generally assigned numerically from W to E and from S to N, just like mile markers. Some numbers fall in between if they come at a later time.