How did the children get their names ^H^H^H^H^H^H numbers?

[Charles2]

I never quite understood why the westernmost spur of I-59 in Alabama was numbered 359 instead of 159, or since I-59 is duplexed with I-20 in western Alabama, why wasn't 120 or 320 used, since I-20 is a more important route than I-59.  Similarly, why wasn't the Birmingham southern bypass numbered 259 instead of 459? And better yet, why isn't the proposed Northern Bypass of Birmingham, which might get completed by the time my great grandchildren start driving, numbered 659 or 859 instead of 422?  The way it is drawn up now, the Northern bypass will end and begin at I-59.

[tidecat]

Alabama has hidden state designations for its interstates.  I-65 is AL 665, I-10 is AL 610, etc.  The I-59 spurs actually are AL 359, AL 459, and AL 759 since those numbers were not in use elsewhere in the system, and it prevents things like AL-6459 in the route logs.

I-359 is a north/south route, so while an x20 is available, it wouldn't make sense.

AL 159 is also in use at Gordo, so I-159 would be an especially poor choice for Tuscaloosa.

One to watch might be AL 85 from Geneva to Fort Rucker.  I have a hunch it may swap catalog numbers with I-85 and I-685, the latter of which is currently on the books as AL 108.  An alternative would be that I-85 has its catalog designation changed to something like AL 385.

[Charles2]

I see your point, but does it necessarily hold water?  Consider:

I-10: Mobile County to Baldwin County; AL-10: Choctaw County to Henry County
I-20: Sumter County to Cleburne County, AL-20: Lauderdale to Limestone County
I-22: Marion County to Jefferson County; AL-22: Dallas County to Randolph County
I-59: Sumter County to DeKalb County; AL-59: Baldwin and Monroe Counties
I-65: Mobile County to Limestone County; AL-65: Jackson County
I-85: Montgomery County (for now, maybe) to Lee County; AL-85: Geneva and Dale Counties
I-165: Mobile County; AL-165: Barbour and Russell Counties

I know that internally all 2-di Interstates in Alabama are designated as AL-6XX; is there a separate designation for all 3-di's?

And evidently ALDoT doesn't seem overly concerned about Interstate or US routes intersecting multiple routes of the same number.  For example:

I-65 junctions both I-10 (in Mobile) and AL-10 (in Greenville).
I-65 junctions both I-20 (in Birmingham) and AL-20 (near Decatur).
I-65 junctions AL-22 (in Clanton) and will junction I-22 (in Birmingham, if and when the interchange is completed).
I-65 junctions both AL-59 (in Bay Minette) and I-59 (in Birmingham)
U.S. 72 junctions both I-65 (in Athens) and AL-65 (at Paint Rock in Jackson County).

I know that in the '50's all state routes that duplicated U.S. routes in the state were eliminated.  I wonder why the same strategy wasn't enacted when Interstate route designations were announced later in the '50's?

[Tom958]

Why, for instance, is the Atlanta bypass 285 instead of an x20?

Probably because I-285 provides a more direct bypass route for I-85 than for I-75 or I-20.

[PurdueBill]

I never quite understood why the westernmost spur of I-59 in Alabama was numbered 359 instead of 159, or since I-59 is duplexed with I-20 in western Alabama, why wasn't 120 or 320 used, since I-20 is a more important route than I-59.  Similarly, why wasn't the Birmingham southern bypass numbered 259 instead of 459? And better yet, why isn't the proposed Northern Bypass of Birmingham, which might get completed by the time my great grandchildren start driving, numbered 659 or 859 instead of 422?  The way it is drawn up now, the Northern bypass will end and begin at I-59.

I wonder if the leading numeral 1 is avoided for the "reason" that certain signs for I-126 and I-129 both have text instead of shields...misreading of the 1 as an I (e.g., "126" read as "I-26" by some), so 1xx is skipped?  Doesn't seem plausible or reasonable that too many people could be doing that, but that's a reason I've read about for the text "I-126" type thing.  Sigh.

I recall that 865 was used because "665" sounded too much like "65" for emergency calls and the whole reason for renumbering there was to have a distinct number, not a new number that was also ambiguous or confusing.

[agentsteel53]

I-710 and I-110: mnemonics as they were upgraded from CA-7 and CA-11, respectively.

no idea if I-505 and I-580 have anything to do with I-5W and US-50.

[Henry]

I-710 and I-110: mnemonics as they were upgraded from CA-7 and CA-11, respectively.

no idea if I-505 and I-580 have anything to do with I-5W and US-50.

I-505 and I-580 were once I-5W, so I believe that Caltrans thought they'd be better off keeping the 5 as the first number when they received their respective 3di designations. If so, this makes a whole lot of sense.

[tidecat]

I see your point, but does it necessarily hold water?  Consider:

I-10: Mobile County to Baldwin County; AL-10: Choctaw County to Henry County
I-20: Sumter County to Cleburne County, AL-20: Lauderdale to Limestone County
I-22: Marion County to Jefferson County; AL-22: Dallas County to Randolph County
I-59: Sumter County to DeKalb County; AL-59: Baldwin and Monroe Counties
I-65: Mobile County to Limestone County; AL-65: Jackson County
I-85: Montgomery County (for now, maybe) to Lee County; AL-85: Geneva and Dale Counties
I-165: Mobile County; AL-165: Barbour and Russell Counties

I know that internally all 2-di Interstates in Alabama are designated as AL-6XX; is there a separate designation for all 3-di's?

And evidently ALDoT doesn't seem overly concerned about Interstate or US routes intersecting multiple routes of the same number.  For example:

I-65 junctions both I-10 (in Mobile) and AL-10 (in Greenville).
I-65 junctions both I-20 (in Birmingham) and AL-20 (near Decatur).
I-65 junctions AL-22 (in Clanton) and will junction I-22 (in Birmingham, if and when the interchange is completed).
I-65 junctions both AL-59 (in Bay Minette) and I-59 (in Birmingham)
U.S. 72 junctions both I-65 (in Athens) and AL-65 (at Paint Rock in Jackson County).

I know that in the '50's all state routes that duplicated U.S. routes in the state were eliminated.  I wonder why the same strategy wasn't enacted when Interstate route designations were announced later in the '50's?

My guess is that there were people with addresses that would have changed.  It also helps that the interstate shields are blue, and not white like Alabama state routes and US routes.

I-165 in Mobile was supposed to be part of the long-canceled I-210 beltway, but AL-210 was built in the 1950s.  It may very well be AL-6165 for inventory purposes, although 365 and 410 were and still are available.

I agree that allowing the duplication may be a poor choice in hindsight given that there will probably be another 2-digit interstate in Alabama's future. If I-14 ever gets built as proposed, it won't be that far from AL 14.

[mrsman]

Then there are examples like I-205 in California. It technically could have been an x80 3di, but it makes perfect sense to be the 205 since it takes you "to I-5"

I feel the same about 580. It could have reasonably been numbered 380, 780 or 980, but it connects both the 5 and the 80.

When 205 was first proposed, it would have not touched an x80 route at all, as 580 then was I-5W (and the current I-5 between Vernalis through Sacramento to Dunnigan was proposed, though never signed, as I-5).

That's one thing that I've always questioned.  Why, with the sheer number of 3di interstates that the Bay Area has, did not CalTrans use a throwaway 2di such as I-3 or I-58 (or some other such number) to free up interstate numbers (I-x80 and I-x05) for use in other places, instead creating monstrosities such as I-238?  I-5W would've been a perfect I-3.

Not I-58 as that would conflict with CA-58 and CA does not allow same numbers.

I always thought that if you were doing a renumbering, I-238, I-580 between I-238 and I-205 and I-205 can be a single 2di.  I-580 connection to I-5, and the I-580 connection from the SF Bay Bridge to I-238 would be two 3dis of the new interstate.  I-580 would now be limited to Richmond-San Rafael without a multiplex on I-80.