Are there guidelines for choosing which interstate gets to "parent" the 3di routes in a certain location?
It's not always the lowest number in a community. In Richmond, I-95 gets to be a parent while I-64 does not. However, in Louisville, I-64 was a parent long before the idea of numbering the Jefferson Gene Snyder Freeway as I-265 was floated. In Atlanta, I-20 is the lowest-numbered 2di, and I-85 is the highest-numbered, and I-85 gets to be the parent. In Birmingham, the middle number (59) is the parent.
I've often wondered the same.
If I had to guess, and this is just that, a guess, they base it on when the routes were planned. In the case of Atlanta, was the routing of I-85 established prior to 75 and 20? I'm not sure, but that might be one factor.
I think for Richmond, it's because the route (I-295) is largely a bypass for I-95 north-south traffic, however the western ~12 mile portion does provide a full east-west bypass for I-64 (one I've used dozens of times) as well, but it's not nearly as long as the ~43 miles of bypass for I-95. The northeastern leg between I-95 and I-64 serves as a joint bypass for both I-64 and I-95 traffic.
As far as the others... VA-895 (planned I-895) is pretty obvious - it links I-95 and I-295. I-195 / VA-195 does link to I-64 on one end, but it also connects both ends to I-95, so that makes more sense.
I also think I-64 numbers in Virginia weren't used due to the heavy concentration / need for 3di numbers in the Hampton Roads region. VA-164, I-264, I-464, I-564, and I-664 are all in use there.
To answer the original question... I would just say it depends on the situation case-by-case.
I would vote for it being case by case basis. Chicagoland's 3DIs are fairly clear as to which number makes the most sense. 294 is clearly an alternate to 94, 290 is clearly an alternate to 90, 190 is clearly a 90 spur, etc.
While not technically an interstate, IL-394 is probably the only one where you could've chosen an x80 number instead of an x94. But I think x94 is a better choice, given how many x80 routes there are across the country.
Milwaukee definitely had other options for 794, could've easily been an x43 number, say 143, and honestly, it's too bad it's not, since 43 has no child routes.
Overall, for bypasses, pick the route that the bypass is more effective or helpful for. For spurs, pick whatever you feel like.
Quote from: JoePCool14 on April 07, 2023, 09:47:24 AM
Milwaukee definitely had other options for 794, could've easily been an x43 number, say 143, and honestly, it's too bad it's not, since 43 has no child routes.
That was established before I-43 existed.
Quote from: Big John on April 07, 2023, 09:55:54 AM
Quote from: JoePCool14 on April 07, 2023, 09:47:24 AM
Milwaukee definitely had other options for 794, could've easily been an x43 number, say 143, and honestly, it's too bad it's not, since 43 has no child routes.
That was established before I-43 existed.
Ah okay, thanks.
Well in my ideal world, I'd call it I-143. (Bonus points: there currently is no WI-143, so it's available!)
Quote from: JoePCool14 on April 07, 2023, 10:03:29 AM
Quote from: Big John on April 07, 2023, 09:55:54 AM
Quote from: JoePCool14 on April 07, 2023, 09:47:24 AM
Milwaukee definitely had other options for 794, could've easily been an x43 number, say 143, and honestly, it's too bad it's not, since 43 has no child routes.
That was established before I-43 existed.
Ah okay, thanks.
Well in my ideal world, I'd call it I-143. (Bonus points: there currently is no WI-143, so it's available!)
Decommissioned in 1996.
Los Angeles has some nice variety, with I-5 and I-10 being parents of three 3di's each. Even I-15 gets in on the action, although technically so, as San Bernardino may be considered the farthest east suburb.
OTOH, for Seattle/Tacoma, I-5 gets two children, but I-90 gets none.
I wonder if beltways generally favor x0 and x5 3di numbers over non-x0 or x5, in addition to what has been mentioned already.
Like I-270 in Columbus could've easily been I-271 instead (it existed before both the existing I-271 and 471), as its north-south sections are longer than its east-west sections, and acts as an I-71 bypass as much as it is an I-70 bypass.
Also, a portion of St Louis's I-270 was I-244 before getting renumbered. Wonder if the x0 favoritism is a reason for it getting renumbered.
I wonder this too. Like why is our loop in Houston interstate 610 and not interstate 245 or 445? Why is San Antonio's interstate 410 and not 435 or even 437 or 837?
Quote from: achilles765 on April 08, 2023, 06:19:57 AM
I wonder this too. Like why is our loop in Houston interstate 610 and not interstate 245 or 445? Why is San Antonio's interstate 410 and not 435 or even 437 or 837?
In those cases, 410 and 610 roll off the tongue better than 435 or 837. Human preference plays a part there. I find those examples more clear cut than 794 vs. 143.
Another unusual example that I realized today: Why is I-576 in Pittsburgh an x76 instead of an x79? Yes, I know it meets I-376, but it doesn't meet I-76 itself, while it does meet I-79. Shouldn't that alone make an x79 number better than an x76? Also, it's north-south, which parallels with I-79 more.
Quote from: SkyPesos on April 08, 2023, 03:24:50 PM
Another unusual example that I realized today: Why is I-576 in Pittsburgh an x76 instead of an x79? Yes, I know it meets I-376, but it doesn't meet I-76 itself, while it does meet I-79. Shouldn't that alone make an x79 number better than an x76? Also, it's north-south, which parallels with I-79 more.
I-576?
Quote from: sprjus4 on April 08, 2023, 05:39:38 PM
Quote from: SkyPesos on April 08, 2023, 03:24:50 PM
Another unusual example that I realized today: Why is I-576 in Pittsburgh an x76 instead of an x79? Yes, I know it meets I-376, but it doesn't meet I-76 itself, while it does meet I-79. Shouldn't that alone make an x79 number better than an x76? Also, it's north-south, which parallels with I-79 more.
I-576?
I think he actually means what is I-579 (the short spur to Pittsburgh's arena district). It had been proposed at one point as I-876 (was there a planned connection to I-376/former I-70/I-76 that was never constructed?)
California generally for the most part has logical 3di numbers. The earliest examples were sequential, but several are derived from past designations of roads.
I-80
180 skipped due to 1934-present Route 180, though I-180 was a temporary designation for former Route 17/post-1984 I-580 extension between San Rafael and Albany
I-280 - partial beltway of SF-San Jose area first proposed in 1950s, oriiginally with a planned terminus at I-480 in the Presidio (today's US 101/Route 1 junction), then a planned but unconstructed terminus at I-80 near the Bay Bridge. Of note: the original 1950s-1960s plans for I-80 would have had 80 end at 280 in Golden Gate Park
I-380 - spur of I-280 to San Francisco International Airport, a replacement number for what had been planned as Route 186. Designated after I-580 came into existence in the late 1960s/early 1970s.
I-480 - was planned in the 1950s as an inner loop around the Marina and Embarcadero (partially built, now demolished) from the foot of the Bay Bridge to today's US 101/Route 1 junction in the Presidio (where Route 1 south of there had been proposed as the northernmost segment of 280 pre-1968)
I-580 - former I-5W between I-80 and I-5, designated 1964
I-680 - east half of Bay Area belt route proposed in 1950s, from San Jose through Concord originally ending in Vallejo, then rerouted in 1976 to Cordelia.
I-780 - former I-680 between Benicia and Vallejo, designated 1976
I-880 (original) - bypass route of old I-80 in West Sacramento and Sacramento. Taken over by I-80 in 1982 as a result of the through-town routing upgrades in North Sacramento being canceled in 1979 in favor of light rail.
I-880 (current) - former Route 17 between the MacArthur Maze and I-280 in San Jose, existed as freeway for 20-30 years before Interstate designation was created in 1984. Not really a loop route but road does link two interstate (even though freeway segment of the remaining Route 17 does continue past I-280 and Route 85)
I-980 - planned Route 24 extension from I-580 west to what is now I-880, also part of a corridor that had been in some proposals for the Southern Crossing project. At the time route was designated (1981), the 480 number still existed in SF, and I-880 along the Nimitz was about 3 years away from happening so this essentially was "spur from I-580 to a non-interstate road".
I-238 - lol
I-5
I-105 (original) - existing US 101 between the East Los Angeles Interchange and the San Bernardino Split. Never signed.
I-105 (current) - connector from LAX/Route 1 east towards I-605 and near, but not at I-5. Spur from I-605 essentially to the airport area and El Segundo.
I-205 - connector between I-580 in Altamont and I-5 in Tracy, essentially a side effect of changes in I-5 (creation of West Side corridor instead of US 99 becoming I-5 here + I-5W not going to Route 132 in Modesto) ca. 1957-1958. Former US 50.
I-305 (unsigned) - funding designation from 1982 onwards for former I-80 in West Sacramento and Sacramento, essentially the Interstate-standard portion along US 50 from I-80 to Route 99, and Route 51 from Route 99 to E Street. Designation created after I-505 was created.
I-405 - west loop of I-5 through West LA, LAX, Long Beach, Costa Mesa. IIRC this existed before I-205 was a thing? Planned in the 1950s along former Route 7 (Sepulveda) as well as a new-terrain corridor from Hawthorne southeast to Irvine.
I-505 - former planned I-5W between Dunnigan and Vacaville, designation is from 1964.
I-605 - connector originally designated between I-405 in Seal Beach and I-10 in El Monte, later extended northeast to I-210. Proposed in the 1950s
I-805 - east bypass of I-5 in San Diego, proposed 1950s (surprising that this wasn't I-205 at the start in retrospect).
I-905 (currently signed as state route) - former Route 75/Route 117 from I-5 southeast to the Otay Mesa border, designation created in 1980s but Interstate signage still has not begun
I-10
I-110 (original) - today's unsigned Route 10 connector along former US 60/70/99 between US 101 and I-5. Never signed.
I-110 (current) - former Route 11/US 6 between US 101 (where southbound signage with the interstate shield begins in earnest) passing by I-10 (where the interstate designation itself actually starts?) to Route 47 in San Pedro. Designation appears to be derived from the former Route 11 numbering and was created in 1981.
I-210 - northern loop of I-10 from San Fernando throug Pasadena originally to Pomona (State Route 210 later extended this loop route functionally to Redlands, and was submitted in the late 90s as possible Interstate but not approved at the time). Proposed in the 1950s.
I-710 - former Route 15/Route 7 along the Long Beach Freeway from I-10/Valley Boulevard near Monterey Park to Route 47 on Terminal Island. Designation created 1984 (at the same time as 880) and is very much derived from the 1964-1983 Route 7 numbering.
I-15
I-215 - lengthy urban loop that is former US 395/I-15/I-15E between Devore and Temecula, passing through San Bernardino and Riverside. Designation created 1982 to replace 1974-1982 I-15E, which itself was created after I-15 was realigned to a new-terrain bypass route from Devore to Temecula that incorporated Route 71/former US 395 and planned Route 31. (note that all of this was still US 395 prior to 1969)
Quote from: TheStranger on April 08, 2023, 06:12:32 PM
Quote from: sprjus4 on April 08, 2023, 05:39:38 PM
Quote from: SkyPesos on April 08, 2023, 03:24:50 PM
Another unusual example that I realized today: Why is I-576 in Pittsburgh an x76 instead of an x79? Yes, I know it meets I-376, but it doesn't meet I-76 itself, while it does meet I-79. Shouldn't that alone make an x79 number better than an x76? Also, it's north-south, which parallels with I-79 more.
I-576?
I think he actually means what is I-579 (the short spur to Pittsburgh's arena district). It had been proposed at one point as I-876 (was there a planned connection to I-376/former I-70/I-76 that was never constructed?)
SkyPesos is referring to PA 576 (AKA PA Turnpike 576).
Quote from: JoePCool14 on April 08, 2023, 10:45:45 AM
Quote from: achilles765 on April 08, 2023, 06:19:57 AM
I wonder this too. Like why is our loop in Houston interstate 610 and not interstate 245 or 445? Why is San Antonio's interstate 410 and not 435 or even 437 or 837?
In those cases, 410 and 610 roll off the tongue better than 435 or 837. Human preference plays a part there.
I've never noticed anyone in Kansas City having any problem rolling 435 off their tongue.
Quote from: sprjus4 on April 08, 2023, 05:39:38 PM
Quote from: SkyPesos on April 08, 2023, 03:24:50 PM
Another unusual example that I realized today: Why is I-576 in Pittsburgh an x76 instead of an x79? Yes, I know it meets I-376, but it doesn't meet I-76 itself, while it does meet I-79. Shouldn't that alone make an x79 number better than an x76? Also, it's north-south, which parallels with I-79 more.
I-576?
Sorry, I meant PA 576. Forgot that it wasn't an interstate, but a state route signed like a 3di.
Quote from: Scott5114 on April 08, 2023, 11:09:55 PM
Quote from: JoePCool14 on April 08, 2023, 10:45:45 AM
Quote from: achilles765 on April 08, 2023, 06:19:57 AM
I wonder this too. Like why is our loop in Houston interstate 610 and not interstate 245 or 445? Why is San Antonio’s interstate 410 and not 435 or even 437 or 837?
In those cases, 410 and 610 roll off the tongue better than 435 or 837. Human preference plays a part there.
I've never noticed anyone in Kansas City having any problem rolling 435 off their tongue.
Yep, I've never seen a problem with the other notable xx5 beltways "not rolling off their tongue" over an xx0 (I-465, I-275, I-495 to name a few)
I've never had an issue with any given number not rolling off the tongue. Some numbers are more fun to say (Route 66, for example). None of them are hard to say and I don't think that was really reasoning for why a number was or wasn't chosen. But it's an interesting idea at the very least. But I also think retaining existing numbers is more important than renumbering something to a 3di, especially nowadays. In the early days this probably made sense as a way to promote the system, but now the design standards and funding are more important. (And I don't think the latter is even a thing anymore). In the case of California, if they could do it over, I'd say just don't even bother with I-238. Just leave it as CA-238, or just keep the whole thing as CA-9 (which it originally was anyway).
What I find interesting is states that have few 3di, not always choosing the lowest available. Like in Nevada, it was I-515 as opposed to either I-115 or I-315. On one hand you could argue this was perhaps due to planned future expansion, but Las Vegas is in the southeast corner of the state, the odds of either a 115 or 315 showing up farther south seems pretty slim. The odd number makes sense given odd leading digits are usually used as spurs, but I've always wondered where that number came from.
Quote from: Quillz on April 09, 2023, 07:44:17 AM
What I find interesting is states that have few 3di, not always choosing the lowest available. Like in Nevada, it was I-515 as opposed to either I-115 or I-315. On one hand you could argue this was perhaps due to planned future expansion, but Las Vegas is in the southeast corner of the state, the odds of either a 115 or 315 showing up farther south seems pretty slim. The odd number makes sense given odd leading digits are usually used as spurs, but I've always wondered where that number came from.
Some states do that to not duplicate with 3di in adjacent states. From what I heard, Milwaukee went with 894 because Chicago had 294 already, and 494 and 694 planned. Similar reason for 794: 194 was on the Kennedy Expy when I-90 used the alignment of existing 290, 394 is a state route 3di, and 594 was the O'hare spur.
Also, Charlotte went with 485 for their beltway because Atlanta already had a well-known 285 beltway.
I never understood why North Carolina went for I-795 rather than I-195, 395, or 595. Maybe for duplication purposes? I can sort of understand why Georgia went for I-985 as the spur to Gainesville. I-185 is taken already in Columbus and I guess they thought that I-385 and I-585 in South Carolina were too close, but 785 was available.
Quote from: Quillz on April 09, 2023, 07:44:17 AM
In the case of California, if they could do it over, I'd say just don't even bother with I-238. Just leave it as CA-238, or just keep the whole thing as CA-9 (which it originally was anyway).
Route 9 north of Los Gatos was already truncated by 1964; the segments between 238 and the current Route 9 terminus were covered by former and current Route 85, Route 237, and Route 262. (if anything, the San Jose-area Route 9 that existed pre-1964 was a hodgepodge corridor that represents several distinct corridors, as seen above).
Quote from: BlueOutback7 on April 09, 2023, 11:47:12 AM
I never understood why North Carolina went for I-795 rather than I-195, 395, or 595. Maybe for duplication purposes?
Probably not I-395 due to only being 200 miles away from Virginia / DC's I-395. I'm not sure why not I-195 or I-595.
Also - the same goes for NC I-587. Why not I-187, I-387, I-787, I-987? None of those exist anywhere, except I-787 near Albany, NY - and that's a separate I-87 system altogether.
Then again, they went with NC I-295 around Fayetteville instead of I-495 or I-695, despite being only around 150 miles from VA I-295. I know I-495 was the designation temporarily used on I-87 (when it was only for Raleigh to I-95), but I believe that came later than the I-295 idea.
Quote from: sprjus4 on April 09, 2023, 03:03:42 PM
Also - the same goes for NC I-587. Why not I-187, I-387, I-787, I-987? None of those exist anywhere, except I-787 near Albany, NY - and that's a separate I-87 system altogether.
There's an I-587 in Kingston NY, though it's a pretty short glorified ramp that ends at roundabouts on both sides. Imo it's fine as just NY 28.
Quote from: SkyPesos on April 09, 2023, 03:59:53 PM
Quote from: sprjus4 on April 09, 2023, 03:03:42 PM
Also - the same goes for NC I-587. Why not I-187, I-387, I-787, I-987? None of those exist anywhere, except I-787 near Albany, NY - and that's a separate I-87 system altogether.
There's an I-587 in Kingston NY, though it's a pretty short glorified ramp that ends at roundabouts on both sides. Imo it's fine as just NY 28.
NYSDOT takes the 90% fed share on it, thank you very much.
^ Maybe the better word would've been an unsigned interstate. Which, it basically already is, save a couple signs.
587 in New York would be a better candidate for being unsigned than 595 in Maryland, in my opinion. Last time I was there, 587 isn't even signed on 87.
Quote from: Scott5114 on April 08, 2023, 11:09:55 PM
Quote from: JoePCool14 on April 08, 2023, 10:45:45 AM
Quote from: achilles765 on April 08, 2023, 06:19:57 AM
I wonder this too. Like why is our loop in Houston interstate 610 and not interstate 245 or 445? Why is San Antonio's interstate 410 and not 435 or even 437 or 837?
In those cases, 410 and 610 roll off the tongue better than 435 or 837. Human preference plays a part there.
I've never noticed anyone in Kansas City having any problem rolling 435 off their tongue.
Quote from: SkyPesos on April 08, 2023, 11:15:34 PM
Yep, I've never seen a problem with the other notable xx5 beltways "not rolling off their tongue" over an xx0 (I-465, I-275, I-495 to name a few)
Quote from: Quillz on April 09, 2023, 07:44:17 AM
I've never had an issue with any given number not rolling off the tongue. Some numbers are more fun to say (Route 66, for example). None of them are hard to say and I don't think that was really reasoning for why a number was or wasn't chosen. But it's an interesting idea at the very least.
Maybe rolling off the tongue wasn't the right way to say it. But it's the number of syllables, shortens how long it takes to say. Saying 410 is
faster than 435. It's not that important.
Quote from: Quillz on April 09, 2023, 07:44:17 AM
But I also think retaining existing numbers is more important than renumbering something to a 3di, especially nowadays.
I disagree. I think we should still try to keep the system in order for the long-term. Better consistency across the country.
Quote from: JoePCool14 on April 10, 2023, 12:12:23 PM
I disagree. I think we should still try to keep the system in order for the long-term. Better consistency across the country.
I wholeheartedly agree. The point of a numbering system is to encode information about the routes into their names to assist the users of the road.
Fortunately the interstate system is not too badly mangled yet, and with relatively minor adjustments it should be possible to keep things consistent.
The US highways are a prime example of what not to do, allowing deviations to accumulate over time you end up with a spaghetti network.
The only issue as far as numbering 3 digits comes up if there is a shortage of numbers in a given state on a given route. 1,3,5,7,9 give 5 spur numbers per state per route, and 2,4,6,8 gives 4 loop numbers. Are there any interstates where this has yet become a problem? California or Texas seem like potential problems, being large and with many urban areas.
Quote from: HighwayStar on April 10, 2023, 02:47:23 PM
The only issue as far as numbering 3 digits comes up if there is a shortage of numbers in a given state on a given route. 1,3,5,7,9 give 5 spur numbers per state per route, and 2,4,6,8 gives 4 loop numbers. Are there any interstates where this has yet become a problem? California or Texas seem like potential problems, being large and with many urban areas.
Yes, I-80 in California is maxed out.
Some states like to use even first digit 3di numbers on any route that connects two interstates, while others only use even first digits on those that connect the parent interstate twice. It seems more likely for states in the former category to max out the 3di numbers, as they really only have 4 numbers per 2di to work with instead of 9 if none or very few of their 3di routes are "dead-end" (relative to the interstate system, can't think of a better word) spurs.
Quote from: JoePCool14 on April 10, 2023, 03:40:21 PM
Quote from: HighwayStar on April 10, 2023, 02:47:23 PM
The only issue as far as numbering 3 digits comes up if there is a shortage of numbers in a given state on a given route. 1,3,5,7,9 give 5 spur numbers per state per route, and 2,4,6,8 gives 4 loop numbers. Are there any interstates where this has yet become a problem? California or Texas seem like potential problems, being large and with many urban areas.
Yes, I-80 in California is maxed out.
I-180 is not in use, although they would have to renumber CA 180.
Quote from: Roadgeekteen on April 10, 2023, 04:13:02 PM
Quote from: JoePCool14 on April 10, 2023, 03:40:21 PM
Quote from: HighwayStar on April 10, 2023, 02:47:23 PM
The only issue as far as numbering 3 digits comes up if there is a shortage of numbers in a given state on a given route. 1,3,5,7,9 give 5 spur numbers per state per route, and 2,4,6,8 gives 4 loop numbers. Are there any interstates where this has yet become a problem? California or Texas seem like potential problems, being large and with many urban areas.
Yes, I-80 in California is maxed out.
I-180 is not in use, although they would have to renumber CA 180.
I-480 is also not in use, and there hasn't been a CA 480 since the Embarcadero Freeway was destroyed in 1989 and decommissioned in 1991. You'd think they could just number I-238 to I-480, but I-480 remains a sore subject in the Bay Area to this day.
Quote from: SkyPesos on April 10, 2023, 03:45:09 PM
Some states like to use even first digit 3di numbers on any route that connects two interstates, while others only use even first digits on those that connect the parent interstate twice. It seems more likely for states in the former category to max out the 3di numbers, as they really only have 4 numbers per 2di to work with instead of 9 if none or very few of their 3di routes are "dead-end" (relative to the interstate system, can't think of a better word) spurs.
The latter states are doing it correctly. The benefit of using the second definition is they have clearly defined a true "loop", ie, if I as a motorist see I-470 coming up I know that it will bring me back to I-70 after we bypass whatever town it is. And as you point out this conserves numbers for other routes.
I was under the impression all that matters is the parent. So a "spur" can connect two interstates as long as it's the parent on one side and another one on the other side.
California ran out of x80 and did use most of them "correctly"
205: incorrect, only touches 5 at one end. could be "fixed" by numbering this one 305, 705, 905. the former and latter are in use (technically, neither are signed), 705 has never been assigned.
405: correct, begins and ends at the 5
605: incorrect, only touches 5 at one end. could again be "fixed" by using 305, 705, 905. but already running into an issue because there aren't enough numbers, assuming spur is being used strictly to refer to only touching its parent once.
805: correct, begins and ends at the 5
280: never meets 80, was supposed to junction with 480, in either case, this would make it more a spur. so 180, 380, 580, 780, 980. which is another issue because 380, 580, 780, 980 are all used "correctly" in the sense they touch their parent once.
So California was bound to run out even if all were being applied properly. This is also one of the reasons why I think the interstate design standards were more important, and completely replacing one state highway number with an interstate number wasn't always the best idea. I would have been in favor of keeping something like CA-21 or CA-35 intact and allowed those 3di numbers be used elsewhere. Another possibility was combining 280 and 680 into something of a half-loop, not quite a beltway but a similar concept.
New York is the only state I know of that presently has used up all available 3di, as there is Interstates 190-990.
IIRC, all the even first digit means is that the route is supposed to meet up with Interstates at both ends, regardless of parent.
Quote from: Quillz on April 10, 2023, 04:53:57 PM
205: incorrect, only touches 5 at one end. could be "fixed" by numbering this one 305, 705, 905. the former and latter are in use (technically, neither are signed), 705 has never been assigned.
1. At one point, this was supposed to connect what was I-5W (now I-580) and what was the 1958-1964 I-5E proposal (now I-5), so that would have technically been both ends at parent.
2. Both ends are at Interstates.
Quote from: Quillz
605: incorrect, only touches 5 at one end. could again be "fixed" by using 305, 705, 905. but already running into an issue because there aren't enough numbers, assuming spur is being used strictly to refer to only touching its parent once.
As noted in the post I did earlier - https://www.aaroads.com/forum/index.php?topic=33145.msg2834973#msg2834973 - 605 as originally proposed linked I-10 (one interstate) with I-405 (another interstate). It isn't a loop/bypass, but it does have Interstates at both ends. (I guess it could be seen as I-10 traffic bypassing downtown LA to get to Long Beach and Orange County)
Quote from: Quillz
280: never meets 80, was supposed to junction with 480, in either case, this would make it more a spur. so 180, 380, 580, 780, 980.
Also mentioned in my earlier post: I-80 was originally planned to terminate at I-280 in Golden Gate Park, prior to the freeway revolts of the 1960s (which caused the cancellation of freeway construction along the 19th Avenue/Junipero Serra corridor past Font Boulevard, and nixed the I-80 Western Freeway entirely from the Central Freeway/Fell Street junction west along the Panhandle park corridor).
After 1968, I-280 was rerouted along former US 101 (Southern Freeway) and one-time proposed Route 87 (along the section from Cesar Chavez (Army) to I-80/Route 480, though only the part to 3rd Street was ever built. The portion from 6th to 3rd was rebuilt as King Street in conjunction with the opening of the Giants' new stadium in 2000.
280 in its 1968-present definition was supposed to have termini at I-80 near Fremont Street, and its current southern terminus at I-680/US 101 (so there is a link to another interstate there).
I can see why 280/680 are separate numbers, for similar reasons as 494/694 in Minneapolis - the two halves of the belt are too distinct rather than square/circular.
Quote from: Quillz on April 10, 2023, 04:53:57 PM
I was under the impression all that matters is the parent. So a "spur" can connect two interstates as long as it's the parent on one side and another one on the other side.
California ran out of x80 and did use most of them "correctly"
205: incorrect, only touches 5 at one end. could be "fixed" by numbering this one 305, 705, 905. the former and latter are in use (technically, neither are signed), 705 has never been assigned.
405: correct, begins and ends at the 5
605: incorrect, only touches 5 at one end. could again be "fixed" by using 305, 705, 905. but already running into an issue because there aren't enough numbers, assuming spur is being used strictly to refer to only touching its parent once.
805: correct, begins and ends at the 5
280: never meets 80, was supposed to junction with 480, in either case, this would make it more a spur. so 180, 380, 580, 780, 980. which is another issue because 380, 580, 780, 980 are all used "correctly" in the sense they touch their parent once.
So California was bound to run out even if all were being applied properly. This is also one of the reasons why I think the interstate design standards were more important, and completely replacing one state highway number with an interstate number wasn't always the best idea. I would have been in favor of keeping something like CA-21 or CA-35 intact and allowed those 3di numbers be used elsewhere. Another possibility was combining 280 and 680 into something of a half-loop, not quite a beltway but a similar concept.
New York is the only state I know of that presently has used up all available 3di, as there is Interstates 190-990.
A potential solution, though awkward and possibly problematic would be to allow the use of 2 digit lead digits, ie 1190, 1290, etc.
In any case, I don't think the interstate was as well provisioned with auxiliary route options as the US numbered system.
Although it was not exactly planned this way and violates it in many cases, the US numbered system in theory has the parent route, 1 or 2 digit, and up to 9 three digit spur routes from the parent route available.
Loops are effectively unlimited, and better yet can be made descriptive by using Bypass, Alternate, Loop, City, Business, Scenic, Truck, Toll, and Historic. Divided routes with cardinal designations add yet another variant to this.
I believe it should be whether it's radial or circumferential. For example, I-291 in Connecticut is correct despite not meeting I-91 at both ends because it's a partial loop around Hartford, not inward or outward. On the other hand, I-270 in Maryland is incorrect because it clearly goes to and from DC.
How is I-270 incorrect? It connects with an interstate on either end.... I-70 (its parent to the north) and I-495 to south.
It's the way to DC. It's not a loop or beltway around anything.
Quote from: sprjus4 on April 10, 2023, 06:02:32 PM
How is I-270 incorrect? It connects with an interstate on either end.... I-70 (its parent to the north) and I-495 to south.
It must connect to the same interstate at both ends to make it a true loop. It should be a spur, hence numbered I-170 for example.
A 3di interstate highway can have an even digit if it connects to an interstate highway on both ends If I-270 terminated in the DC metro with no connection to I-495 or any other interstate highway, then an odd digit would be appropriate.
It connects to I-70 to the north and I-495 on the south. An even digit is perfectly appropriate.
Quote from: sprjus4 on April 10, 2023, 08:58:53 PM
A 3di interstate highway can have an even digit if it connects to an interstate highway on both ends If I-270 terminated in the DC metro with no connection to I-495 or any other interstate highway, then an odd digit would be appropriate.
It connects to I-70 to the north and I-495 on the south. An even digit is perfectly appropriate.
Illinois tends to deploy the "Odd" first digit in cases of only touching the parent once, regardless if both ends are Interstates or not
I-155 has one end on 55 and the other on 74
I-355* has one end on 80 and the other on 290. Former southern end was 55
I-190 has one end on 90 and the other at ORD airport
I-180 has one end on 80...the other a lot of nothing
I-172 has one end on 72 and one end on IL 110/336
When the I-490 Tollway is completed and signed, it will be the first "Even" first digit 3di in IL that only touches its parent once
I-355 was proposed, and maps were even printed before before its opening, of it getting the I-455 designation, but obviously that did not happen
Quote from: SkyPesos on April 08, 2023, 03:24:50 PM
Another unusual example that I realized today: Why is I-576 in Pittsburgh an x76 instead of an x79? Yes, I know it meets I-376, but it doesn't meet I-76 itself, while it does meet I-79. Shouldn't that alone make an x79 number better than an x76? Also, it's north-south, which parallels with I-79 more.
My best guess would be that Pennsylvanians tend to associate 76 with toll roads, so 576 fits right in with 276, 376, and 476, all of whom are tolled or have tolled segments. I-79 is free for its entirety as well.
In Southern California, I-605 and I-710 are essentially parallel freeways, both initially proposed as extending from I-10 southward (605 was later extended north; 710 was planned to be extended north, later cancelled).
Yet why is one an I-x05 and the other an I-x10? If one wanted to maintain a mnemonic link between CA-7 and its replacement, I-705 was just as available as I-710. (And 610 available instead of 605, unless someone wanted to reserve that for a potential CA-60 renumbering.)
As for why one was a "loop" and the other a "spur", both ends of I-605 are at another interstate (I-10 initially, I-210 currently to I-405), but the south end of I-710 has always extended into Long Beach and does not end at another Interstate.
Quote from: GaryA on April 11, 2023, 04:09:35 PM
As for why one was a "loop" and the other a "spur", both ends of I-605 are at another interstate (I-10 initially, I-210 currently to I-405), but the south end of I-710 has always extended into Long Beach and does not end at another Interstate.
Interestingly, the 1963-1965 definiton of Route 7 included what is now Route 47 between the Harbor and Terminal Island Freeways - by the time I-710 was designated, I-110 already existed on the Harbor Freeway, but that middle segment between San Pedro and 47/103 is still not full freeway to this day (with the one remaining intersection at Navy Avenue).
The configuration of I-710 at Route 47 along Seaside has 47 exiting itself and 103 and 710 each beginning from that spot, with 103 following 47 from the diamond interchange ramps north to the Terminal Island Freeway. Basically, the through lane configuration today has a number change, but would have fit the 1963-1965 definition of Route 7.
A thought just occurred to me: In a perfect world, I-4 would have some 3di's in Orlando, but the 4xx toll roads there make it appear as though they could be adopted by it. Which, as it is, could also qualify as a route numbering coincidence.
Quote from: Quillz on April 09, 2023, 07:44:17 AM
I've never had an issue with any given number not rolling off the tongue. Some numbers are more fun to say (Route 66, for example). None of them are hard to say and I don't think that was really reasoning for why a number was or wasn't chosen. But it's an interesting idea at the very least. But I also think retaining existing numbers is more important than renumbering something to a 3di, especially nowadays. In the early days this probably made sense as a way to promote the system, but now the design standards and funding are more important. (And I don't think the latter is even a thing anymore). In the case of California, if they could do it over, I'd say just don't even bother with I-238. Just leave it as CA-238, or just keep the whole thing as CA-9 (which it originally was anyway).
An important point to remember is that I-238 carries a significant volume of truck traffic due to the ban on big rigs on I-580 through Oakland. I believe part of the stated reason for having an interstate designation was to convey to long-distance truck traffic, particularly in the era before GPS, that this was a high-quality interestate-grade connector and not just any old state highway. That Interstate shield conveys certain expectations for a highway that a state or US shield does not.
Quote from: Quillz on April 09, 2023, 07:44:17 AM
What I find interesting is states that have few 3di, not always choosing the lowest available. Like in Nevada, it was I-515 as opposed to either I-115 or I-315. On one hand you could argue this was perhaps due to planned future expansion, but Las Vegas is in the southeast corner of the state, the odds of either a 115 or 315 showing up farther south seems pretty slim. The odd number makes sense given odd leading digits are usually used as spurs, but I've always wondered where that number came from.
I've always speculated that Nevada using 515 and 580 instead of lower available spur numbers has to do with how the state route numbers were assigned in the 1976 renumbering–both interstates being in various planning stages at the time of the renumbering. Routes numbers in the 500 and 600 series were assigned to urban routes (FAU funding scheme), so assigning numbers beginning with "5" to these urban interstate spurs made sense. (Had 515 and 580 not been assigned to interstate spurs, they would have been assigned to roads in a different part of the state, based on the number clustering model adopted during the renumbering. A hypothetical SR 515 would have been assigned to a road in Carson City, and a hypothetical SR 580 would likely have been located along an east/west section line arterial in the Las Vegas area.
Also, Nevada doesn't use the same number in different systems. An SR 115 was assigned near Fallon during the renumbering, and while I don't think an SR 315 (or FAP 315) was ever assigned, "315" likely fell in the "gap for future expansion" between numbers assigned in Lander and Lincoln counties.
Quote from: I-55 on April 10, 2023, 09:20:06 PM
Quote from: SkyPesos on April 08, 2023, 03:24:50 PM
Another unusual example that I realized today: Why is I-576 in Pittsburgh an x76 instead of an x79? Yes, I know it meets I-376, but it doesn't meet I-76 itself, while it does meet I-79. Shouldn't that alone make an x79 number better than an x76? Also, it's north-south, which parallels with I-79 more.
My best guess would be that Pennsylvanians tend to associate 76 with toll roads, so 576 fits right in with 276, 376, and 476, all of whom are tolled or have tolled segments. I-79 is free for its entirety as well.
At first, I thought about the fact that PA-TPK-576 didn't go to I-79 for 15 years until just about a year and a half ago could factor in. Though at the time the "Findlay Connector" opened in 2006, current I-376 near the airport was still PA-60. Though I think it was pretty much a given at that point that it would be renumbered to I-376.
Also, way back in the day, I'd speculate (and only speculation) that when the Mon-Fayette was supposed to "Y" into a highway going toward downtown (since taken off the table) and the other leg to the Parkway East (I-376) in Monroreville, the 576 number would be concurrent with TPK-43 from the future interchange (if/when built) near the Washington/Allegheny County line to where they'd have split near the Monongahela River, with TPK-43 heading toward downtown in the cancelled highway, and 576 meeting back up with 376 in Monroeville (creating a true Southern Beltway, with 376 as both termini).
Or, maybe the people that actually get to choose the numbers didn't put quite as much thought into it as people here do.
A variant of the topic is picking the parent for a 3di that has its applicable end(s) at a junction where two 2dis run concurrently -- for example, I-359 in Tuscaloosa, AL (spur with a terminus at I-20/I-59) or I-280 outside Toledo, OH (southern terminus at I-80/I-90).
Also, I've seen concurrent US routes have concurrent business loops (WY); why couldn't concurrent 2dis have concurrent 3dis?
I know it's been a couple of weeks, but....
Quote from: HighwayStar on April 10, 2023, 06:19:39 PM
Quote from: sprjus4 on April 10, 2023, 06:02:32 PM
How is I-270 incorrect? It connects with an interstate on either end.... I-70 (its parent to the north) and I-495 to south.
It must connect to the same interstate at both ends to make it a true loop. It should be a spur, hence numbered I-170 for example.
An auxiliary interstate does not need to be a loop to be eligible for an even first digit. Even first digits are intended to communicate that it is a "connecting" auxiliary interstate.
I-270 in Maryland connects I-70 and I-495, and therefore is eligible for an even first digit.
I-291 in Connecticut connects I-84 and I-91 and therefore is eligible for an even first digit.
Quote from: 1 on April 10, 2023, 05:43:48 PM
I believe it should be whether it's radial or circumferential. For example, I-291 in Connecticut is correct despite not meeting I-91 at both ends because it's a partial loop around Hartford, not inward or outward. On the other hand, I-270 in Maryland is incorrect because it clearly goes to and from DC.
"Radial" and "circumferential" quickly lose meaning when dealing with large urban areas with multiple dense nodes, such as Los Angeles (where many of the 3di are in grid layout anyway), or regional areas with multiple urban centers, such as the NC urban region containing Raleigh-Durham-Chapel Hill, as well as the one containing Greensboro--Winston-Salem--High Point.