What's the Number of This 2di?

[Henry]

I present to you a list of the currently-existing 2di's and a clue to identify each one. If you can think of better questions than the ones shown in bold, feel free to do so. This is what I came up with for the routes below:

The longest Interstate in Hawaii: H-1
The only H-series Interstate that's signed north-south: H-2
The H-series Interstate that goes through two tunnels, and ends at a Marine Corps base: H-3
The one that runs along the bottom of Texas: I-2
The diagonal route that splits Florida in half: I-4
The West Coast route that once had a western branch into the Bay Area: I-5
The Phoenix bypass route that leads to San Diego: I-8
The cross-country route that has the longest in-state segment of all: I-10
The new route that will one day connect Las Vegas to Phoenix: I-11
The one that is a northern bypass of New Orleans: I-12
The one that exists in Texas, but has plans to stretch across the Deep South: I-14
The one that goes from San Diego to Montana via Las Vegas and Salt Lake City: I-15
The one that slices Georgia in half: I-16
The route that starts at an unusually high exit number and crosses I-10 twice in Phoenix: I-17
The one that's signed entirely in metric: I-19
The one that can take you from Dallas to Atlanta: I-20
The Memphis-Birmingham upgrade of US 78: I-22
The diagonal route that dips into Georgia before returning to Tennessee: I-24
The one that parallels the Rocky Mountains: I-25
The one that used to exist only in the Carolinas, but now extends into Tennessee: I-26
The short route that connects two mid-size cities in the Texas Panhandle: I-27
The one that connects Kansas City to the Dakotas: I-29
The shortest route to end in a 0: I-30
The only one that still has two split routes: I-35
The San Antonio-Corpus Christi route: I-37
The US 51 upgrade that also has a triple-concurrency with I-90 and I-94: I-39
The Barstow-Wilmington Interstate that seems to go through so many route changes: I-40
The one that replaced a US highway of the same number: I-41
The one that's currently being built in North Carolina, and may also exist in Oklahoma as a separate route: I-42
The Milwaukee-Green Bay route that also connects to Beloit: I-43
The one that uses three toll roads in Oklahoma: I-44
The Houston-Dallas route: I-45
The one that has a large gap in Arkansas and doesn't quite reach downtown Kansas City: I-49
The one that parallels the Mississippi River, but then turns northeast to reach Chicago: I-55
The one that will connect Chicago to Little Rock: I-57
The Deep South route that has a long concurrency with I-20: I-59
The one that has you going the wrong way to reach its eastern terminus: I-64
The one that goes through Birmingham, Nashville, Louisville and Indianapolis before stopping short of Chicago: I-65
The one that exists in Virginia and Washington, DC, but once had routing proposals further west that are now cancelled: I-66
The one that's disambiguated by a sign near an exit for a state route of the same number: I-68
The one that used to exist only in Indiana and Michigan, but is being extended to Texas: I-69
The one that ended at a parking lot in Baltimore: I-70
The one that connects Louisville to the three largest cities in Ohio: I-71
The one that exists mostly in Illinois and ends just after crossing the Mississippi River: I-72
The Rockingham-Greensboro route that is part of an ambitiously-planned corridor stretching from Myrtle Beach to Michigan: I-73
The one that goes from the Quad Cities to Cincinnati, and has some out-of-place sections in the Southeast: I-74
The one that used to end in Tampa, but was later extended to Miami along Alligator Alley: I-75
The one that has separate sections going to Denver and Philadelphia: I-76
The one that connects Charlotte to Cleveland: I-77
The one that runs on a pair of one-way streets in Jersey City: I-78
The one that bypasses Pittsburgh and has a spur leading there: I-79
The cross-country route that misses both New York and Chicago by a few miles: I-80
The one that runs parallel to the Appalachians, and is getting a reroute in Syracuse: I-81
The out-of-place route that looks more north-south than east-west, and can be used as a shortcut from Salt Lake City to Seattle: I-82
The Baltimore-Harrisburg route that's seen proposals to extend to both Rochester, NY and Greensboro, NC: I-83
The one with two separate parts leading to Portland, OR and Hartford, CT: I-84
The Southeastern route that looks more east-west than north-south, and crosses over several lower-numbered 2dis along the way: I-85
The one that's had three sections existing in Idaho, Pennsylvania and New York State, and formerly in Connecticut and Massachusetts: I-86
The New York City-Montreal route that is getting a separate section going from Raleigh, NC to Norfolk, VA: I-87
The one that has two separate sections in Illinois and New York State: I-88
The one that has a future connection to an Autoroute in Quebec: I-89
The longest 2di, stretching from Seattle to Boston: I-90
The one that has two spurs of the same number within 50 miles of each other, serving Hartford, CT and Springfield, MA: I-91
The one that goes through the Big Dig in Boston, and has a two-lane section through Franconia Notch: I-93
The Main Street of the Midwest, connecting to Detroit, Chicago, Milwaukee and Minneapolis/St. Paul: I-94
The route that connects the Northeastern megalopolis to Maine and Miami: I-95
The Michigan Interstate that switched routes with a spur in Grand Rapids: I-96
The route that's so short it exists within one Maryland county: I-97
The out-of-place route located in the middle of Pennsylvania: I-99

[hotdogPi]

The one that slices Georgia in half: I-16

This fits better for I-75.

[ilpt4u]

The one that slices Georgia in half: I-16

This fits better for I-75.

I like "Only Interstate in Michigan's Upper Peninsula" for 75

[Henry]

Here's a revised version of the list, with a new entry:

The longest Interstate in Hawaii: H-1
The only H-series Interstate that's signed north-south: H-2
The H-series Interstate that goes through two tunnels, and ends at a Marine Corps base: H-3
The one that runs along the bottom of Texas: I-2
The diagonal route that splits Florida in half: I-4
The West Coast route that once had a western branch into the Bay Area: I-5
The Phoenix bypass route that leads to San Diego: I-8
The cross-country route that has the longest in-state segment of all: I-10
The new route that will one day connect Las Vegas to Phoenix: I-11
The one that is a northern bypass of New Orleans: I-12
The one that exists in Texas, but has plans to stretch across the Deep South: I-14
The one that goes from San Diego to Montana via Las Vegas and Salt Lake City: I-15
The Macon-Savannah route: I-16
The route that starts at an unusually high exit number and crosses I-10 twice in Phoenix: I-17
The one that's signed entirely in metric: I-19
The one that can take you from Dallas to Atlanta: I-20
The Memphis-Birmingham upgrade of US 78: I-22
The diagonal route that dips into Georgia before returning to Tennessee: I-24
The one that parallels the Rocky Mountains: I-25
The one that used to exist only in the Carolinas, but now extends into Tennessee: I-26
The short route that connects two mid-size cities in the Texas Panhandle: I-27
The one that connects Kansas City to the Dakotas: I-29
The shortest route to end in a 0: I-30
The only one that still has two split routes: I-35
The San Antonio-Corpus Christi route: I-37
The nonexistent parent of a Bay Area spur: I-38
The US 51 upgrade that also has a triple-concurrency with I-90 and I-94: I-39
The Barstow-Wilmington Interstate that seems to go through so many route changes: I-40
The one that replaced a US highway of the same number: I-41
The one that's currently being built in North Carolina, and may also exist in Oklahoma as a separate route: I-42
The Milwaukee-Green Bay route that also connects to Beloit: I-43
The one that uses three toll roads in Oklahoma: I-44
The Houston-Dallas route: I-45
The one that has a large gap in Arkansas and doesn't quite reach downtown Kansas City: I-49
The one that parallels the Mississippi River, but then turns northeast to reach Chicago: I-55
The one that will connect Chicago to Little Rock: I-57
The Deep South route that has a long concurrency with I-20: I-59
The one that has you going the wrong way to reach its eastern terminus: I-64
The one that goes through Birmingham, Nashville, Louisville and Indianapolis before stopping short of Chicago: I-65
The one that exists in Virginia and Washington, DC, but once had routing proposals further west that are now cancelled: I-66
The one that's disambiguated by a sign near an exit for a state route of the same number: I-68
The one that used to exist only in Indiana and Michigan, but is being extended to Texas: I-69
The one that ended at a parking lot in Baltimore: I-70
The one that connects Louisville to the three largest cities in Ohio: I-71
The one that exists mostly in Illinois and ends just after crossing the Mississippi River: I-72
The Rockingham-Greensboro route that is part of an ambitiously-planned corridor stretching from Myrtle Beach to Michigan: I-73
The one that goes from the Quad Cities to Cincinnati, and has some out-of-place sections in the Southeast: I-74
The one that used to end in Tampa, but was later extended to Miami along Alligator Alley: I-75
The one that has separate sections going to Denver and Philadelphia: I-76
The one that connects Charlotte to Cleveland: I-77
The one that runs on a pair of one-way streets in Jersey City: I-78
The one that bypasses Pittsburgh and has a spur leading there: I-79
The cross-country route that misses both New York and Chicago by a few miles: I-80
The one that runs parallel to the Appalachians, and is getting a reroute in Syracuse: I-81
The out-of-place route that looks more north-south than east-west, and can be used as a shortcut from Salt Lake City to Seattle: I-82
The Baltimore-Harrisburg route that's seen proposals to extend to both Rochester, NY and Greensboro, NC: I-83
The one with two separate parts leading to Portland, OR and Hartford, CT: I-84
The Southeastern route that looks more east-west than north-south, and crosses over several lower-numbered 2dis along the way: I-85
The one that's had three sections existing in Idaho, Pennsylvania and New York State, and formerly in Connecticut and Massachusetts: I-86
The New York City-Montreal route that is getting a separate section going from Raleigh, NC to Norfolk, VA: I-87
The one that has two separate sections in Illinois and New York State: I-88
The one that has a future connection to an Autoroute in Quebec: I-89
The longest 2di, stretching from Seattle to Boston: I-90
The one that has two spurs of the same number within 50 miles of each other, serving Hartford, CT and Springfield, MA: I-91
The one that goes through the Big Dig in Boston, and has a two-lane section through Franconia Notch: I-93
The Main Street of the Midwest, connecting to Detroit, Chicago, Milwaukee and Minneapolis/St. Paul: I-94
The one that connects the Northeastern megalopolis to Maine and Miami: I-95
The Michigan Interstate that switched routes with a spur in Grand Rapids: I-96
The one that's so short it exists within one Maryland county: I-97
The out-of-place route located in the middle of Pennsylvania: I-99

[NE2]

The one with the poo:

[bassoon1986]

I wonder if there are ways to make some of these less descriptive and more of a riddle?

The only 2di interstate to continue as its spur route at its terminus

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

[pderocco]

They should be Jeopardy answers.

[NE2]

The only 2di interstate to continue as its spur route at its terminus

I-20.

[pderocco]

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Three: I-5 (Castaic CA), I-8 (Ligurta AZ), and I-85 (Thomasvile NC).

[NE2]

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Three: I-5 (Castaic CA), I-8 (Ligurta AZ), and I-85 (Thomasvile NC).

77 (Charlotte NC). 70 (Breezewood PA) though not in the same way.

[cockroachking]

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Three: I-5 (Castaic CA), I-8 (Ligurta AZ), and I-85 (Thomasvile NC).

77 (Charlotte NC). 70 (Breezewood PA) though not in the same way.

Also I-20 and I-59 in Birmingham, AL.

[hotdogPi]

I think I have a better one: The one that parallels Nebraska but never enters: I-29

[1995hoo]

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Three: I-5 (Castaic CA), I-8 (Ligurta AZ), and I-85 (Thomasvile NC).

77 (Charlotte NC). 70 (Breezewood PA) though not in the same way.

And I-95 and I-695 in Maryland previously both had their carriageways cross over each other at their interchange with each other, but that interchange was rebuilt and the crossovers no longer exist.

[webny99]

The one that's had three sections existing in Idaho, Pennsylvania and New York State and formerly in Connecticut and Massachusetts: I-86

This one can be simplified considerably. 

[vdeane]

I wonder if there are ways to make some of these less descriptive and more of a riddle?

The only 2di interstate to continue as its spur route at its terminus

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Indeed.  It looks like they're more interesting in the lower numbers, but quickly get purely descriptive as we move north/east, either because the OP doesn't know the rest of the country well enough to come up with better entries or because they got into "just put something down to finish it" mode.

The longest 2di, stretching from Seattle to Boston: I-90

Are you including the portion of I-90 that's a bootleg interstate?

[pderocco]

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Three: I-5 (Castaic CA), I-8 (Ligurta AZ), and I-85 (Thomasvile NC).

77 (Charlotte NC). 70 (Breezewood PA) though not in the same way.

And I-95 and I-695 in Maryland previously both had their carriageways cross over each other at their interchange with each other, but that interchange was rebuilt and the crossovers no longer exist.

Those are something different, like the freeway equivalent to a DDI. I-5 and I-8 (not to mention AZ-87) were built that way because one side was the original alignment and the other was built much later with a gentler slope over a longer distance, which needed to be used for downhill traffic. And I-85 was built that way to allow a single rest area to be shared, yet having the ramps to the rest area on the right. In the end, they didn't exactly "share" the rest area, but that's what someone on the original project said.

[Henry]

I think I have a better one: The one that parallels Nebraska but never enters: I-29

I actually like this one better! Although it does run through the Omaha metropolitan area, it never actually enters the city itself, instead going through Council Bluffs, IA.

The only 2di interstate to continue as its spur route at its terminus

I-20.

Not even close; it's I-45, but the spur route is not even signed!

If anyone else thinks they can write better clues for the rest, have at it!

[bassoon1986]

I think I have a better one: The one that parallels Nebraska but never enters: I-29

I actually like this one better! Although it does run through the Omaha metropolitan area, it never actually enters the city itself, instead going through Council Bluffs, IA.

The only 2di interstate to continue as its spur route at its terminus

I-20.

Not even close; it's I-45, but the spur route is not even signed!

If anyone else thinks they can write better clues for the rest, have at it!

Yes I was thinking I-45 turning into I-345. I-20 turns into a Bus Interstate route.

I knew I-8 carriageways crossed but I couldn't place I-85. I was looking in Birginia.

[freebrickproductions]

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Three: I-5 (Castaic CA), I-8 (Ligurta AZ), and I-85 (Thomasvile NC).

77 (Charlotte NC). 70 (Breezewood PA) though not in the same way.

Also I-20 and I-59 in Birmingham, AL.

I-65 at that same interchange as well.

[NE2]

The only 2di interstate to continue as its spur route at its terminus

I-20.

Not even close; it's I-45, but the spur route is not even signed!

How is this not I-20's spur route? https://travelmapping.net/hb/showroute.php?r=sc.i020bsflo

[kurumi]

For this particular 2di:
* one signed instance exists today
* one proposed instance (which intersects the present one) was signed with a different number
* another proposed instance was also renumbered before being signed

[thenetwork]

I wonder if there are ways to make some of these less descriptive and more of a riddle?

The only 2di interstate to continue as its spur route at its terminus

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

That will go up by one in a few years, once the I-70/Floyd Hill project is completed west of Denver.

[jlam]

I wonder if there are ways to make some of these less descriptive and more of a riddle?

The only 2di interstate to continue as its spur route at its terminus

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

That will go up by one in a few years, once the I-70/Floyd Hill project is completed west of Denver.

I may be wrong, but there are 5, right?

I-5 near Castaic
I-8 near Fortuna Foothills
I-20 at I-65 in Birmingham
I-65 at I-20 in Birmingham
I-85 near Lexington

At least that's all I can think of

[cockroachking]

The only interstate to have its carriageways criss cross over one another. (I think I'm wrong and there are 2 of these...)

Three: I-5 (Castaic CA), I-8 (Ligurta AZ), and I-85 (Thomasvile NC).

77 (Charlotte NC). 70 (Breezewood PA) though not in the same way.

Also I-20 and I-59 in Birmingham, AL.

I-65 at that same interchange as well.

That's right. I forgot that it was a double crossover.

[Henry]

The only 2di interstate to continue as its spur route at its terminus

I-20.

Not even close; it's I-45, but the spur route is not even signed!

How is this not I-20's spur route? https://travelmapping.net/hb/showroute.php?r=sc.i020bsflo

For the sake of this thread, Business Spurs don't count.