Skipping the lowest spur

[vtk]

Maybe an answer to the following question can inject some needed historical insight:  Was the numbering of 3-digit Interstates from the Yellow Book plan (original 41,000 miles) done by AASHO, or did AASHO simply approve the numbers that individual states submitted?

The latter: http://cahighways.org/097-104.html#102

Well then, obviously California wasn't trying to make geographically-ordered 3dIs. 

[Stephane Dumas]

. I'll add one: In Quebec, there are two A-440s and A-540s. But A-840 and A-940 are unused numbers. Why not put those over in Quebec City instead of duplicating numbers from Montreal? (The Montreal A-440 doesn't even come close to meeting A-440, and may as well be an X25.) Then you also have A-955 without a 755 or 555 and a 973 without a 773.

There'll be one less A-540 soon. The Montreal A-540 will be renumbered as a part of A-30 extension
http://www.mtq.gouv.qc.ca/portal/page/portal/Librairie/Publications/fr/grands_projets/a30_parachevement/a-30_carte_sorties_grande.pdf

[Michael in Philly]

Yes, but the point is there's no rule saying that 3dis have to go in numeric order across the state.

My point was, apparently New York did try to do that, at least with I-90; the fact that 990 is out of order is explainable by the fact that it was added after the others were in place.

[Eth]

It's hard to say if Georgia was explicitly trying to have a progression across the state, but if so it's worked out reasonably well - the only one "out of place" is I-675, which wasn't added until the 1980s and is between I-475 and I-575.  Even the proposed-but-never-built Interstates would fit in such a progression, with 175 being south of 475, 420 being west of 520, and the originally proposed 475 (not the one in Macon) being south of 575; 485, I believe, would've been entirely inside 285, so I suppose that also fits in a way.

[Scott5114]

A related question is why some three-digit Interstates do not receive lower first digits.  Taking the example of I-35 in Kansas, why do we not have the following number assignments in lieu of what actually exists:

*  I-235 beltway around Kansas City metropolitan area (presently I-435)

*  I-435 connector between I-29 in Missouri and I-35 in Kansas (presently I-635)

*  I-635 Wichita western bypass (presently I-235)

What would be the benefit to this compared to the current setup? As it stands, going from south to north on I-35 (the same way the mileposts are reckoned), you see I-135, I-235, I-335, I-435, I-635, in that order.

[vdeane]

You seem to be under the impression that this was a rule in the past, everywhere, which has necessarily been broken by new additions.  In some states, there is evidence for this, but I certainly don't believe it to be universally true.  Besides this thread, the only time I'd heard of such a progression concept was in reference to Michigan, and, now that I think about it, possibly with the 3dUS highways.  But 3dUS highways and 3dI loops & spurs are quite different in nature. 

Where did you get that impression from?  The reason I used the x90s is because I'm not familiar with any other example where the 3dis aren't entirely in order.  There was never any rule, the states just kinda did it.  Perhaps MA or VT could be used as examples, with 3dis out of place form where one would expect for this kind of rule, but in the absence of additional 3dis they're still in order.

[Kacie Jane]

Yes, but the point is there's no rule saying that 3dis have to go in numeric order across the state.

My point was, apparently New York did try to do that, at least with I-90; the fact that 990 is out of order is explainable by the fact that it was added after the others were in place.

With I-87 as well.  187, 287, 387, and 487 were all in the NYC area.  All would have been in place with each other, with the exception of the first 487 (Cross-Westchester Expressway) which was south (actually east) of 287, although 287 was locked into place by New Jersey.  Then 587 is in Kingston, and proposed 687 and current 787 are both in Albany.

Regarding the "is this a rule?", my understanding is that the states choose the 3di number when they apply to AASHO, and they say yay or nay.  I think the answer is generally no, but some states chose to follow such a guideline when they were picking numbers.

[J N Winkler]

What would be the benefit to this compared to the current setup? As it stands, going from south to north on I-35 (the same way the mileposts are reckoned), you see I-135, I-235, I-335, I-435, I-635, in that order.

The feature ("benefit" is probably too strong a term) of the numbering I outlined is that the larger metropolitan area gets the lower three-digit numbers.  It could be argued that, particularly in situations where potential three-digit routes outnumber possible choices for three-digit Interstate route number, it makes more sense to allocate numbers first to the large metropolitan areas since it is in those places that the traffic demand for Interstate-type facilities is most firmly established.

In actuality, I suspect Kansas (with Missouri's cooperation and BPR's approval) allocated three-digit numbers in the order in which the relevant routes were planned and built, without operating a number reservation scheme.  I-235 was mostly finished (Turnpike interchange to Broadway) by 1962, while I think construction on I-435 and I-635 started a little later.  At the beginning of original Interstate construction, I suspect few if any states tried reserving three-digit route numbers by size of metropolitan area because it would have taken considerable foresight to predict the numerous ways in which the Interstate network would be expanded beyond the original plan.

BTW, the neat milepost ordering of three-digit routes for I-35 in Kansas you outline is, to an extent, artificial.  Originally, in 1962, there was no I-135.  I-235 interchanged directly with the Turnpike; I-35W came along later and its numbering change to I-135 came still later.  I-335 is an artifact of the 65 MPH speed law.

[empirestate]

Yes, but the point is there's no rule saying that 3dis have to go in numeric order across the state.

My point was, apparently New York did try to do that, at least with I-90; the fact that 990 is out of order is explainable by the fact that it was added after the others were in place.

With I-87 as well.  187, 287, 387, and 487 were all in the NYC area.  All would have been in place with each other, with the exception of the first 487 (Cross-Westchester Expressway) which was south (actually east) of 287, although 287 was locked into place by New Jersey.  Then 587 is in Kingston, and proposed 687 and current 787 are both in Albany.

Regarding the "is this a rule?", my understanding is that the states choose the 3di number when they apply to AASHO, and they say yay or nay.  I think the answer is generally no, but some states chose to follow such a guideline when they were picking numbers.

I'd say there is no question that NYS intends to number 3dis in order, looking both at I-90 and I-87. And now there's evidence for it with I-81 as well: I-281 was changed long ago to I-481, as Syracuse is right in the middle of the route. And the new spur in Watertown is numbered 781, perhaps because it's so far north along the route; they could just as easily have gone with 181 or 381.

Other states like TN show a propensity for this: 240, 440, 640 from west to east. Any more?

[hbelkins]

I wonder if Tennessee and Virginia collaborated on the numbering of I-81's spurs. I-181 from Kingsport down to Johnson City; I-381 in Bristol, I-581 in Roanoke. Was Bristol considered to be too close to Tennessee's I-181 to permit Virginia's use of that number for the Bristol connector?

It obviously didn't factor into numbering I-265 and I-275 in Tennessee and Kentucky.

[Takumi]

I-364 was also never used in Virginia, although it was proposed for I-464. I think this is because there was a VA 364 already around, albeit well away from Hampton Roads, by the time I-564 was assigned.

[achilles765]

Here in Texas (which has a surprising lack of 3dis for a state this big, with this many Interstate routes (four or five of which are major routes), and with as extensive a freeway network as we do. 

There are only 6 in the whole state, two of which are secret unsigned routes.  The signed routes are all beltways or semi-beltways which necessitates an even number spur.  In their placement, however, it seems perfect.  IH 110 is (while unsigned) in El Paso, right after entering Texas, 410 in San Antonio, 610 in Houston.  The only silly one is the secret IH 345 in Dallas which is essentially a one mile extension of 45, which ends at IH 30.  So if any 3dis are ever issued here in Houston or between Houston and Dallas, the numbers will be out of order.

Kinda not exactly what the topic discusses, but it does explain why the Dallas beltway is 635 and not 235.  235 is skipped in case there is ever a belt or bypass of, say, Austin or Waco.

[bassoon1986]

820 is almost silly because it's not like Fort Worth is right near the TX/LA border. (Thankfully Tyler's loop will be a TX State Loop). 820 was more likely chosen because of Amon Carter's radio station though.  And we all know 420 won't ever be chosen.


Louisiana's 3di's work nicely on I-10 as well. Other than hidden 910, all the spurs line up nicely (110-Baton Rouge, 310 NO west side, and 510 NO east.)  The loops work too. 210 is in Lake Charles right near Texas, the planned 410 has been an idea for New Orleans and now for Baton Rouge, and 610 is downtown New Orleans.