Types of 3dis

[NE2]

494/694 is obviously a beltway.

[TheHighwayMan3561]

494/694 is obviously a beltway.

Yes, but as separate routes they serve different functions - and MNDot no longer advertises 494 as part of the bypass route.

[Takumi]

Military spurs: I-564 and I-781

[hotdogPi]

I-495 (MA):

Half beltway (not a bypass of I-95 though)

But it also serves as a Lowell-Lawrence-Haverhill connector (and is also part of the way from most of the United States to Maine).

A rare example of a 3di over 100 miles (and turning it into a 2di makes no sense).

[NE2]

494/694 is obviously a beltway.

Yes, but as separate routes they serve different functions - and MNDot no longer advertises 494 as part of the bypass route.

A beltway is not always a good bypass. See I-275 around Cinci.

[empirestate]

Loop from a parent into a nearby city (I-490 NY)

I would call that a business loop.  I-490 is similar to the I-95 business route for Fayetteville NC.  The difference being the latter is not a freeway for it's entire length.  But they serve the same purpose.  The main interstate does not directly serve the city.  So the business loop serves the city for the main route.

The name that was occurring to me was "remote city loop", to connote that it serves a city that the parent route avoids, but "business loop" does suit another aspect of its function.

Oregon and Washington:
I-205 - Loop within a city/alternate to parent (and formally planned to be half of a circumferential)
I-405 (both) - Loop within a city/alternate to parent

I-405 OR seems to me quite a different animal from I-405 WA or I-205, because of its path through only the central city rather than traversing much of the metro area.

I-535: Spur into a city
I-394: Spur into a city
I-694: Bypass/alternate to parent

I-494 is hard for me to peg because it doesn't really neatly fit into any of the categories. It goes out of the way too much to be either a bypass or alternate to I-94, and also serves a number of major MSP suburbs on its own accord. It's basically its own animal with an x94 attached to it.

I-535, a spur into Superior, rather than a spur away from Duluth? It does sort of have a dual function; another such example would be I-190 NY, which is both a spur into Buffalo and a longer-distance spur to Niagara Falls.

For I-694, is there a distinction to be made between "bypass" and "alternate"? The latter seems to suggest more equivalence between two options, while a "bypass" seems like a route that's clearly less local than the through route.

Military spurs: I-564 and I-781

Good addition. Perhaps these, along with airport spurs and some others (I-180 IL) could be subsets of a category called "facility spurs"?

[english si]

orphan (I-278)
Jesus (I-238)

I disagree.  Jesus had Mary (which should be at least half of I-38, therefore... oh hell, it's I-19!)

Is I-238 an 'Adam' then?

[Brandon]

orphan (I-278)
Jesus (I-238)

I disagree.  Jesus had Mary (which should be at least half of I-38, therefore... oh hell, it's I-19!)

Is I-238 an 'Adam' then?

More like Frankenstein's Monster.

[ET21]

The "exit ramps" 

I can think of a few Chicagoland examples:

I-190: Spur into the main airport (O'Hare)
I-290: North/west bypass
I-294: Half-beltway around city
I-355: Two-way spur off I-55

Airport spur is an important addition; there are definitely a few of those (I-380 CA, I-105 CA–but that's also a crosstown sort of route, more than simply an airport spur).

I-355 is interesting: it sure looks like a bypass, but the first digit tells us it's a spur, so...?

I-355 is becoming more of a suburban spur. Still would consider it a bypass (bypass of bypass maybe??)

[DandyDan]

Incest 3DI: I-495/DC Beltway When a 3di and 2Di that were meant to be seperate ended up becoming one and the same.

I can think of I-87/287 in New York, I-80/580 in San Francisco, and the aforementioned. Are there any other examples?

I-94/694 in Minnesota

There's also the spur to the middle of nowhere, of which there is I-180 (IL), I-172 and I-155 (MO-TN), possibly others I missed.

[OCGuy81]

We could always go with the unsigned

I-305 (CA)
I-345 (TX)
I-444 (OK)

And so on.

[Bickendan]

I'd peg I-394 more as a spur away from a city than into (though the portion running east from I-94 qualifies it).

[Pete from Boston]

I-495 in Maine, anyone?  Is there a "You shoulda seen me, kid–I was somebody!" category?

[cl94]

Military spurs: I-564 and I-781

Numbers don't reflect it, but you could consider I-H2 and I-H3 to fall in this category

[Charles2]

I-210 (CA)
I-110 (CA)

3-dis that continue as same numbered state routes.  I'd say 238, but I think that's better in the "orphan" category.

I-759 (AL)

[cjk374]

I-520, Augusta, GA:  odd first digit for a bypass loop? 

[Big John]

I-520, Augusta, GA:  odd first digit for a bypass loop? 

It was originally a spur before it was extended on the east side to reconnect.

[empirestate]

I-520, Augusta, GA:  odd first digit for a bypass loop? 

It was originally a spur before it was extended on the east side to reconnect.

Yeah, that's a wrench in the works. Then again, look as I-526, which is a very similar half-loop bypass, except that the parent bisects it instead of forming the base of the loop. Can we say that whatever "type" I-526 is, I-520 is the same type?


iPhone

[TheStranger]

Yeah, that's a wrench in the works. Then again, look as I-526, which is a very similar half-loop bypass, except that the parent bisects it instead of forming the base of the loop. Can we say that whatever "type" I-526 is, I-520 is the same type?

Would I-140 in Wilmington also fit this as well?

[roadman65]

I-495 on Long Island acts as its own independent interstate.  In fact for Long Islanders it is known locally as the LIE, which serves as the region's backbone freeway.

[empirestate]

Yeah, that's a wrench in the works. Then again, look as I-526, which is a very similar half-loop bypass, except that the parent bisects it instead of forming the base of the loop. Can we say that whatever "type" I-526 is, I-520 is the same type?

Would I-140 in Wilmington also fit this as well?

Maybe, depending on how much is actually built and designated yet. On closer inspection, right now it looks more like a right-angle cutoff between the "east" and "north" quadrants than a full half-loop (and then another separate cutoff on the west side).


iPhone

[TheCatalyst31]

Should I-180 IL get a "just kind of there" category? Technically it's a spur to a city, but the "city" in question has 750 people, and the steel plant it was meant to serve closed. Are there any other spurs like that which don't have a real purpose anymore?

[relaxok]

What would I-380 south of SF be considered?

It's only a couple miles long and was basically added because living along 280 meant it was pretty terrible to get to the SFO airport on US-101 via back roads.

[Revive 755]

Should I-180 IL get a "just kind of there" category? Technically it's a spur to a city, but the "city" in question has 750 people, and the steel plant it was meant to serve closed.

How about "pork spur"?  I am sure there are plenty of other steel plants in the US that could have used an interstate spur.

[SSOWorld]

I-794 - "Bridge"
I-894 - "Redundant" (true definition: bypass)