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3di first digit: any difference between lower and higher numbers?

Started by hotdogPi, November 26, 2017, 09:54:50 AM

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hotdogPi

I used to think that 1xx and 2xx routes were on average longer than those above 600. However, this is not the case; the correlation is actually slightly negative with long routes like I-580 (CA) and I-840 (TN), and very short I-110 (TX), I-195 (ME and FL), and I-291 (CT). [I'm only including routes that have more than one 3di of that type, so routes like I-189 (VT) are excluded.]

However, it seems that newer routes get higher first digits. I'm thinking of I-990 (NY), which was built after the other I-x90s in New York, and very recent I-840 (TN) and I-785 (NC). In fact, looking at this Wikipedia page, all non-I-x69 3dis that were formed from 2012 to 2017 have a first digit of 4 or higher. The 18 listed "proposed" don't quite have as strong a "high number" correlation, but the only 1xx is an I-169. (The correlation is stronger if you exclude North Carolina.)

On the other hand, there were no I-9xx routes for quite a while after 3dis started existing. Even-first-digit 3dis seem to have less of a correlation with date formed; there were several early 6xx routes as well as I-820 in DFW despite other numbers being available.

Is this newer/older correlation actually there, or am I just seeing patterns that don't exist? Are there any (other) correlations between low/high first digits of 3dis?
Clinched, minus I-93 (I'm missing a few miles and my file is incorrect)

Traveled, plus US 13, 44, and 50, and several state routes

I will be in Burlington VT for the eclipse.


Flint1979

The pattern in Michigan just goes from the state line. Like along I-75 you have I-275 first, then I-375, then I-475, then I-675. Along I-96 starting in the west you have the unsigned I-196, I-296 (unsigned in GR), then I-496, then I-696. I-94 just has I-194 in Battle Creek and I-69 doesn't have any three digit highways in the state.

Don't know if I've noticed this before because in Ohio along I-75 it goes I-275, I-675 and then I-475, seems like Dayton and Toledo should be the other way around.

Scott5114

The first digit means nothing other than it being even or odd. A state specifies the desired number in its AASHTO application and if it meets the numbering scheme, AASHTO approves it. 

Usually they simply use them in order. The first loop built off I-33 will be I-233, the second will be I-433, and so forth. Some states made an effort to make the numbers in the initial system increase going from south to north/west to east, but due to coordination with other states this wasn't always possible, and now that additional routes have been added to the system, the progression is often now out of order.

Because state road agencies are free to choose whatever route numbers they like, there are plenty of exceptions to using the lowest numbers first. There are a number of reasons to justify skipping numbers. For example, California uses all of the x80s except for I-180 because they didn't want to conflict with existing CA-180. Georgia skips I-420 for reasons that should be obvious with a bit of research. The story with I-820 in Texas is a little unclear, but I understand it had something to do with a Fort Worth radio station with that number.

A good example of a "clean" 3di system is Oklahoma. There are four 3dis, and three of them are 2xx routes of the appropriate 2di. The one duplicate, an x44, is given the number I-444.

Unless it's changed recently, the only state to use all possible 3dis is New York, in x90s.
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Eth

Quote from: Scott5114 on November 26, 2017, 10:16:21 AM
Georgia skips I-420 for reasons that should be obvious with a bit of research.

There was to be an I-420 (proposed in 1978, partially built as the GA 166 freeway); I don't know if that connotation existed at that time or not.

I don't know for sure if Georgia puts any meaning behind initial first digits, but if you squint you can make out what might be an attempt at positional ordering.

x16: 516 is at the east end of the route, but given its path it's entirely plausible that GDOT simply couldn't envision any more than two other spurs west of there possibly being needed.
x20: 520 is at the east end of the route. This one seems iffier, with plenty of room for more than two spurs elsewhere and the proposed 420 being well over 100 miles to the west. Also, I don't know where a theoretical 220 would have been.
x24: none, most likely ever
x59: none, most likely ever
x75: 175 was proposed in south Georgia, but never built. 475 in Macon and 675 in south metro Atlanta make sense. 575 would seem to work better as 775 in this scenario, but it's not egregious (and maybe they didn't want the double first digit, which could also explain 420 over 220).
x85: 185 makes perfect sense. 285 is reasonable, especially since there was also a proposed 485 in Atlanta. 985 seems slightly strange, but plausible (e.g. GA 14 Conn as I-385, the Freedom Pkwy stub as I-585 had it remained a full freeway, and GA 316 as I-785).
x95: none

jp the roadgeek

My understanding is that if they were created when the Interstate Highway System was first planned, they were supposed to progress higher from south to north and west to east, and if they were created later, they would receive the lowest odd or even option available.  However, different states have different rules as to whether to allow interstate and state routes with the same number; in CT and RI, it is strictly forbidden, there is only one exception in MA (I-295 and MA 295), and in NY, there are several examples of duplication.  Using NY as an example, I-190 to I-890 all progress from west to east (I-190 and I-290 serve Buffalo, I-390, I-490, and I-590 all serve Rochester, I-690 serves Syracuse, I-790 serves Utica, and I-890 serves Schenectady).  I-990 was the only number available for the new spur in the Buffalo area, therefore it violated the west-east rule.  I-384 was chosen instead of I-184 in CT because ConnDOT felt it was easier than renumbering CT 184.  I-395 in CT was obviously chosen over I-195 because MA already has I-195.  And the progression of even I-91's in CT are due to their creation dates: I-291 came first, followed by I-491, and then I-691 much later.
Interstates I've clinched: 97, 290 (MA), 291 (CT), 291 (MA), 293, 295 (DE-NJ-PA), 295 (RI-MA), 384, 391, 395 (CT-MA), 395 (MD), 495 (DE), 610 (LA), 684, 691, 695 (MD), 695 (NY), 795 (MD)

sparker

Quote from: jp the roadgeek on November 26, 2017, 01:26:07 PM
My understanding is that if they were created when the Interstate Highway System was first planned, they were supposed to progress higher from south to north and west to east, and if they were created later, they would receive the lowest odd or even option available.  However, different states have different rules as to whether to allow interstate and state routes with the same number; in CT and RI, it is strictly forbidden, there is only one exception in MA (I-295 and MA 295), and in NY, there are several examples of duplication.  Using NY as an example, I-190 to I-890 all progress from west to east (I-190 and I-290 serve Buffalo, I-390, I-490, and I-590 all serve Rochester, I-690 serves Syracuse, I-790 serves Utica, and I-890 serves Schenectady).  I-990 was the only number available for the new spur in the Buffalo area, therefore it violated the west-east rule.  I-384 was chosen instead of I-184 in CT because ConnDOT felt it was easier than renumbering CT 184.  I-395 in CT was obviously chosen over I-195 because MA already has I-195.  And the progression of even I-91's in CT are due to their creation dates: I-291 came first, followed by I-491, and then I-691 much later.

With respect to 3di's in California, the deployment of such, for the most part, was quite similar in some respects but quite different in others.  The 3di's stemming from I-5, for instance, were originally planned as reversed in order from the usual south-to-north arrangement.  Because of the split of the route into I-5W and I-5E from 1958 through 1963, the number "205" was held in reserve, depending upon how the final routing through Sacramento was handled.  Originally, when I-5E was supposed to have utilized (then) US 99 from the south, the Division of Highways figured that the main trunk route through Sacramento's city center would likely be similarly convoluted as the original 99E/99W routings had been over the years; a I-205 bypass through West Sacramento was thought to be a way to expedite through N-S traffic.  When the alignment was shifted to the LRN 238 (Westside) corridor at the end of '57, that bypass concept became moot.  Originally, I-5 was to do a simple split once it reached US 50 near Tracy, with 5W and 5E following US 50 in those directions.  But that would have added mileage to the overall trip for both branches, so by the end of 1959 the "Tracy Triangle" concept came into being, with the I-205 designation being applied, as it is today, to the top/E-W segment of the triangle (of course, 5 years later the E/W split was gone and I-580 had replaced I-5W).  205 was the northernmost of the CA 3di I-5 subsidiaries; the rest of the even numbers were arrayed according to the northernmost junction with the I-5 trunk; I-405 was next, departing in Sylmar, with I-605 intersecting the parent route in Downey; I-805 in metro San Diego completed the set.  The only odd-prefixed original 3di was I-105 in central L.A.; that was the sole "spur" from I-5.  I-505 was applied at the end of 1963 to the former northern section of I-5W from Vacaville to Dunnigan (old LRN 90); since the number "580" was selected to drive home the point that the corridor connedted 5 with 80, 505 was chosen as a complementary route.  The on-paper-only I-305 was added in 1982 simply as a placeholder for funding of rehab funds to the old I-80 route through Sacramento, while I-905, added later that decade, was likely numbered that way because it was virtually at the southern end of I-5.  The only other trunk route with multiple 3di's under the original plan was I-80; its "children" followed normal procedure.  I-280 was, in fact, to be the western terminus of trunk I-80 in the west part of San Francisco, followed by I-480, which intersected I-80 at the western foot of the Bay Bridge; then I-680, originally hitting I-80 in Vallejo, and the original I-880 alignment, which was the northern Sacramento bypass; no spurs were originally planned.  Of course, in the end things didn't work out as planned: 280 never intersected I-80, 480 was deleted, 680's junction eventually moved to Cordelia, and the trunk I-80 supplanted I-880 in the Sacramento area, with I-880 being re-deployed in the East Bay some four years later.  California's iconoclastic nature has really come into play with Interstate numbering schemes, both in regards to selection and sequencing of 3di numbers.

dgolub

Quote from: 1 on November 26, 2017, 09:54:50 AM
However, it seems that newer routes get higher first digits. I'm thinking of I-990 (NY), which was built after the other I-x90s in New York, and very recent I-840 (TN) and I-785 (NC). In fact, looking at this Wikipedia page, all non-I-x69 3dis that were formed from 2012 to 2017 have a first digit of 4 or higher. The 18 listed "proposed" don't quite have as strong a "high number" correlation, but the only 1xx is an I-169. (The correlation is stronger if you exclude North Carolina.)

The rest of the I-x90 in New York progress from west to east, beginning with I-190 near Buffalo to I-890 near Albany.  I'm assuming that I-990 was added later once the others were already numbered.

OCGuy81

Oregon could have had a clean system too. I-105 in Eugene being the furthest south, the proposed 305 in Salem, and the proposed 505 in Portland.

Then there's 205 and 405 as you go north.

Sadly, Oregon hates freeways, so may 305 and 505 RIP

hotdogPi

Quote from: OCGuy81 on November 27, 2017, 11:58:39 AM
Oregon could have had a clean system too. I-105 in Eugene being the furthest south, the proposed 305 in Salem, and the proposed 505 in Portland.

Then there's 205 and 405 as you go north.

Sadly, Oregon hates freeways, so may 305 and 505 RIP

How is it not a clean system? Given that there is one odd x05, and there are two even x05s, the system is still perfect. The lack of an I-305 doesn't change anything given that there are no higher odd x05 routes.
Clinched, minus I-93 (I'm missing a few miles and my file is incorrect)

Traveled, plus US 13, 44, and 50, and several state routes

I will be in Burlington VT for the eclipse.

OCGuy81

Quote from: 1 on November 27, 2017, 12:20:11 PM
Quote from: OCGuy81 on November 27, 2017, 11:58:39 AM
Oregon could have had a clean system too. I-105 in Eugene being the furthest south, the proposed 305 in Salem, and the proposed 505 in Portland.

Then there's 205 and 405 as you go north.

Sadly, Oregon hates freeways, so may 305 and 505 RIP

How is it not a clean system? Given that there is one odd x05, and there are two even x05s, the system is still perfect. The lack of an I-305 doesn't change anything given that there are no higher odd x05 routes.

Sorry, I guess it is clean. I meant to say they could've had an extended, clean, system.

Charles2

At least for now, Alabama is a "clean" state:

59: 359 in Tuscaloosa, 459 around Birmingham, 759 in Gadsden
65: 165 in Mobile, 565 in Huntsville (although 765 would probably make more sense, since Huntsville is so far north in the state)

I don't necessarily like 685 as the number for what is now I-85 in Montgomery, if and when the southern bypass is built and I-85 is re-routed on the bypass.  Since Montgomery in the middle of the state, 485 would have worked as well.  The "plus" to 685 is that there is no interstate route with that number in Georgia, South Carolina, North Carolina or Virginia.

If the Northern Beltline around Birmingham is ever built, I guess 422 makes decent sense for that route.  Problem is, by the time it's completed (scheduled now for 2054), I doubt I'll be around to care.  I'm 57 years old now; by 2054, I would be 94.

triplemultiplex

Wisconsin ostensibly went for higher 3di's (794 & 894) in Milwaukee due to proximity to Chicago and their lower numbered x94's (proposed and extant).

Tennessee is another example with some semblance of order; the original even x40's increase west to east with 240 in Memphis, 440 in Nashville and 640 in Knoxville.


When I do fictional mapping, I select numbers based on what numbers would "stand out" for clarity in a given area.  As an example; if I'm adding 3di's to the other Houston loops, I'm not going to use another 6xx unless that's the only first number left.  So I go for I-445 when I want to upgrade the TX 8 loop. And stick with the proposed 269 for the Grand Parkway.  I feel that makes it much more obvious which loop one is talking about.  You can also see how I used 3di's from different parents for each loop to further drive home that clarity.
On a map, you'd see 269, 445 and 610; numbers you are not going to get confused if you're getting or giving directions or producing ad copy or listening to a traffic report.

Granted, there are not many places where this is an issue, but it does guide my number selection in metros with more than one 3di.
Under this guideline, Kentucky really dropped the ball having both an I-264 and an I-265.
"That's just like... your opinion, man."

Beltway

I-564 is used as the only Interstate spur from I-64 in Virginia.

Routes 164 and 364 were already in use in 1956 as state primary routes, so to avoid duplication the Navy Base Spur was assigned Interstate 564.
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Ian

Traveling northbound on I-95 in Maine, you'll encounter its three signed 3di's (195, 295, 395) in sequential order. I-495 (both current unsigned Falmouth Spur segment and historic Maine Turnpike alignment) is out of place as it's well south of 395, though it's still north of the southernmost 295 interchange.

In New Hampshire, I-93's two 3di's (293, 393) are also sequential going south-to-north.

Quote from: Beltway on November 28, 2017, 11:18:22 PM
Routes 164 and 364 were already in use in 1956 as state primary routes, so to avoid duplication the Navy Base Spur was assigned Interstate 564.

Maine decided to use I-195 for the spur to Old Orchard Beach despite there already being a state route 195 elsewhere. There is a non-issue, however, as I-195 is almost 200 miles away from its state route counterpart. It's also the only route number duplicate I know of in Maine not counting suffixed routes.
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JCinSummerfield

Quote from: Flint1979 on November 26, 2017, 10:01:13 AM
... Along I-96 starting in the west you have the unsigned I-196, I-296 (unsigned in GR)...

When did I-196 become unsigned?

kphoger

Quote from: JCinSummerfield on November 30, 2017, 03:56:50 PM
Quote from: Flint1979 on November 26, 2017, 10:01:13 AM
... Along I-96 starting in the west you have the unsigned I-196, I-296 (unsigned in GR)...

When did I-196 become unsigned?

In the post you quoted, it is 296 that's unsigned, not 196.
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Beltway

Quote from: Ian on November 29, 2017, 01:54:56 AM
Quote from: Beltway on November 28, 2017, 11:18:22 PM
Routes 164 and 364 were already in use in 1956 as state primary routes, so to avoid duplication the Navy Base Spur was assigned Interstate 564.
Maine decided to use I-195 for the spur to Old Orchard Beach despite there already being a state route 195 elsewhere. There is a non-issue, however, as I-195 is almost 200 miles away from its state route counterpart. It's also the only route number duplicate I know of in Maine not counting suffixed routes.

I don't have any issue with duplication if the roads are widely separated.  But many states don't believe in duplications, including Virginia, even though they do have a few.
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Henry

CA has the cleanest route system out there, with a well-organized group of numbers. It has used up all nine possible 3di's off I-80 (including I-180 for a brief time before it was renumbered as an extension of I-580 due to the existence of CA 180), plus eight of nine for I-5 (I-305 is unsigned, I-905 is reserved as a future route, and I-705 is unused). However, my one complaint would be the sudden jump from I-210 to I-710 when I-310, I-410, I-510 and I-610 could've been used, but otherwise, well thought out.
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kphoger

Quote from: Henry on December 01, 2017, 09:41:09 AM
CA has the cleanest route system out there, with a well-organized group of numbers. It has used up all nine possible 3di's off I-80 (including I-180 for a brief time before it was renumbered as an extension of I-580 due to the existence of CA 180), plus eight of nine for I-5 (I-305 is unsigned, I-905 is reserved as a future route, and I-705 is unused). However, my one complaint would be the sudden jump from I-210 to I-710 when I-310, I-410, I-510 and I-610 could've been used, but otherwise, well thought out.

Arizona and New Mexico are cleaner.  Spotless, you might say.   :sombrero:
Keep right except to pass.  Yes.  You.
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sparker

Quote from: Henry on December 01, 2017, 09:41:09 AM
CA has the cleanest route system out there, with a well-organized group of numbers. It has used up all nine possible 3di's off I-80 (including I-180 for a brief time before it was renumbered as an extension of I-580 due to the existence of CA 180), plus eight of nine for I-5 (I-305 is unsigned, I-905 is reserved as a future route, and I-705 is unused). However, my one complaint would be the sudden jump from I-210 to I-710 when I-310, I-410, I-510 and I-610 could've been used, but otherwise, well thought out.

The I-710 designation was used as a reference to the previous state designation, CA 7; it was thought that retaining that integer would reduce transition issues.

kkt

Quote from: Henry on December 01, 2017, 09:41:09 AM
CA has the cleanest route system out there, with a well-organized group of numbers. It has used up all nine possible 3di's off I-80 (including I-180 for a brief time before it was renumbered as an extension of I-580 due to the existence of CA 180), plus eight of nine for I-5 (I-305 is unsigned, I-905 is reserved as a future route, and I-705 is unused). However, my one complaint would be the sudden jump from I-210 to I-710 when I-310, I-410, I-510 and I-610 could've been used, but otherwise, well thought out.

I think a route system that has NO room for expansion is poorly thought out.

jwolfer

It seems that sometimes neighboring stats will "work" together on 3dis.. eg 275 in Tampa area, 475 Macon and 675 Atlanta.

I don't get why Georgia had i516 in Savannah unless there was a desire to leave room for future or planned and never approved or never built Spurs from i16

Z981




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