Where do you think each unused 2di Interstate number is most likely?

[Flint1979]

1 Doesn't it already exist in Hawaii?

Hawaii has H-1. Alaska has (unsigned) A-1. Puerto Rico has (unsigned) PRI-1.

All three are parts of distinct Interstate networks, added after the main Interstate network was established in the 1950s. None of them get in the way of a mainland I-1.

I can't see any possible place for an I-1 to go. US 101 in CA would have to be I-3 because of CA-1.

Have you been to Wisconsin or North Carolina lately?

Caltrans never reuses a number twice regardless if it's for an Interstate, US Highway or State Highway. So for example I-5 is used for an Interstate so they won't use route 5 for a State highway. US highway there already is a US-5 in New England.

[paulthemapguy]

0.  If we for some reason we don't like the "H" designations in Hawaii, I'd put this on I-H1.
1.  Anchorage to Wasilla, AK.  Or maybe a replacement for I-H3
3.  I-505 and I-880 in CA, plus US101 from San Jose to Los Angeles.
6.  I-69W, which absolutely should not have an odd number.
7.  CA-14
9.  CA-99
13.  Calexico to Indio
14.  US290 (shhh the one by Killeen doesn't exist)
18.  US190 corridor (aka current I-14)
21 & 23. I have no idea
28. I-44 SW of OK City if it gets extended west to Lubbock or points west.
31. I-135 in KS
32. Replaces I-30 because they decided I-85 would be better with an even number, I-30
33. I-35W in MN
34. US74 from Wilmington west to I-26.  The I-74 designation in NC can piss off.
36. US70 corridor east of Raleigh, aka current I-42.  When I-40 east of Raleigh gets removed
from its current north-south routing and uses US64 instead, this will make sense.
38.  US264 east of Raleigh (again, if I-40 gets moved to US64 this will make sense)
42.  US421 west from Winston Salem, NC
46.  Cimarron, Muskogee Tpk. Plus Broken Arrow Expy in OK.
47.  Avenue of the Saints
48.  Cumberland Pkwy and Hal Rogers Pkwy
51.  US51 in WI/IL, aka current I-39
52.  Something in CA probably.
53.  I-41 when I-57 gets routed to replace I-43 north of Milwaukee
54.  US58 corridor in VA
56.  Western Kentucky Pkwy
58.  I-580 and I-205 in CA
60.  I-64 if US60 gets a renumbered.  I envisioned an I-60 from Utah to St. Louis to Virginia Beach to eliminate the duplicity of even numbers like I-76
61.  Natcher and Audobon Pkwys.
62.  New number for I-76 in CO if I-70 becomes I-60
63.  US41/IN-63 from Evansville N through Terre Haute to Chicagoland, or maybe Lafayette
67.  US31 north of Indianapolis to I-196 to Grand Rapids, then US131 north to Cadillac, MI
92.  NH-101 and I-89, hoping for some kind of floating bridge west from the Burlington, VT area across Lake Champlain, as unlikely as it sounds
98.  WI-29

[mrsman]

I-9 or I-13 for a full freeway international freight corridor from I-10 in Indio to Mexicali.

Hey, if it'll help get the Westmorland bypass built, then I-13 might be feasible.  Most of the expressway along CA 111, CA 78, and CA 86 meets Interstate geometric standards (it's CA's closest equivalent to the classic upper-Midwest expressway/freeway facility, with some interchanges but mostly at-grade intersections).  I've used that combination many times as a long-range Phoenix bypass -- if you realize that you're going to hit PHX anywhere near commute times, it's one hell of a lot quicker to use this expressway to get from I-10 to I-8 and vice-versa for congestion avoidance.

I strongly favor having one number for the Indio calexico corridor.  If the whole thing is interstate quality, let it be 13 as suggested.  If not, let's pick one state number and avoid the current confusion.

Nexus 5X

[sparker]

^^^^^^^^
Ironically, the reality is that the Indio-Calexico corridor (aka CA's "mini-NAFTA" route) may get more chopped-up, designation-wise, than it is today.  The section of CA 86 between CA 111 southeast of El Centro to Brawley is reportedly up on the chopping block for relinquishment; it's been effectively bypassed a few miles to the east by the CA 111 expressway, part of the continuum that includes the Brawley Bypass (shared by CA 111 and CA 78).  Once the relinquishment occurs, CA 86 becomes a useless multiplex south of its current west junction with CA 78.  It probably won't happen until Westmorland is bypassed -- but the chances are that CA 86 will eventually be truncated back to that junction, with CA 78 being the sole signed number SE from there to CA 111 east of Brawley.  As of late, Caltrans hasn't seemed that interested in maintaining continuously numbered through routes statewide -- something that has been discussed and decried in this forum for some time now. 

Since the "NAFTA" route also includes the relatively new CA 7 corridor extending south from I-8 to the Mexican border east of Calexico and intended to serve as the principal truck customs corridor in the region, it wouldn't be a stretch to envision the entire 111/78/86 routing -- if it is ever decided to deploy a single number for the corridor -- as being renumbered as CA 7 -- if Caltrans ever regains its sense of propriety regarding such things.  And thus by extension -- if the completed expressway is ever slated for an Interstate upgrade, simply changing the signage to I-7 wouldn't be a stretch either! (although "I-13" would be slightly less annoying, grid-wise).  But any such action would be decades away at best.

[DandyDan]

I personally like the idea of I-33 taking over the Sioux City/Twin Cities corridor. It could be extended to Lincoln, NE as well. The Iowa section that is now IA 60 could revert to its original number.

[sparker]

I personally like the idea of I-33 taking over the Sioux City/Twin Cities corridor. It could be extended to Lincoln, NE as well. The Iowa section that is now IA 60 could revert to its original number.

........and that's the number I neglected to include in my original "likely" batch -- but further south -- at least initially.  For something more short-term, I figured I-33 as replacing I-135 from Wichita to I-70, and extending north along US 81 to I-80 near York; much of the route is upgradeable (Concordia will require a bypass, of course), and it provides access from I-80 south while avoiding Denver and KC chokepoints respectively.  And the 2005 "Safetea-LU" HPC corridor additions included a branch up 135 and 81 to Norfolk before turning NE along NE 35 to Sioux City.  The routing described above along US 75, MSR 60, and US 169 would be a logical extension of that corridor.  However, snaking it along the Minnesota River from Mankato to the Twin Cities might entail quite a few environmental issues requiring a new-terrain bypass route out of the river "bottomland".  While not a "slam dunk", so to speak, the southernmost portion (south of I-80) of this overall corridor concept would be considerably more feasible, development-wise, than the remainder to the north.