Types of 3dis

[empirestate]

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.

Well, my answer for it was "airport spur" or the broader category "facility spur".

[NE2]

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?

I-69 in MS.

[andy3175]

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.

Well, my answer for it was "airport spur" or the broader category "facility spur".

380 was intended to be longer (extending west of I-280), but it does serve a purpose in providing part of the most direct route from the Golden Gate Bridge to SFO via CA 1, I-280, and I-380. Despite its through numbering, US 101 is not the faster route between these two points (most of the time).

[kkt]

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.

I thought of 380 as the way to get from 101 on the peninsula to the Golden Gate Bridge via 19th Ave. and Park Presidio Blvd. in S.F., much faster than following 101 up Van Ness.

[relaxok]

Those routes are actually usually comparable in time (I take both often).

[kkt]

Those routes are actually usually comparable in time (I take both often).

Okay, I'll take your word for it.  CA 1 is prettier and less annoying though.

[Zzonkmiles]

Well intentioned shortcut that scares drivers away with the word "TOLL:"  I-185 (SC)
Coastal area traffic funnel: I-526 (SC), I-516 (GA)

[froggie]

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

Especially I-H3, which shares a distinction with I-781 as ending directly at the entrance to a military facility (both I-H2 and I-564 end near such facilities, but directly at the gate).

[Henry]

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

Especially I-H3, which shares a distinction with I-781 as ending directly at the entrance to a military facility (both I-H2 and I-564 end near such facilities, but directly at the gate).

And I-185 in GA should go into this category as well.

[Thing 342]

Coastal area traffic funnel: I-526 (SC), I-516 (GA)

It would be more accurate to call these traffic deltas as they divert a large amount of beach-bound traffic around the coastal city. I-140 and possibly I-664 would also fit into this category. 

[froggie]

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

Especially I-H3, which shares a distinction with I-781 as ending directly at the entrance to a military facility (both I-H2 and I-564 end near such facilities, but directly at the gate).

And I-185 in GA should go into this category as well.

The freeway extends into Fort Benning, but I-185 itself doesn't...it ends at the 27/280 interchange.  Whereas 781 and H3 end almost literally at the base gate.

[lepidopteran]

I-195 in NJ:  Double spur, leading to a "beltway" in one direction (I-295) and a toll road (GSP) in the other

I-370 in MD:  Formerly a glorified exit ramp off of a 2di, to a subway station.  Now a seamless lead-in to a toll road (MD-200/ICC)

I-470 in OH/WV: Bypass of a tunnel (not to be confused with I-895 in MD, which only takes you through a different tunnel)

In the Atlanta, GA area:
-- I-575: Spur leading from outside of a city to way outside of a city?
-- I-675: Shortcut to a beltway?

[Pete from Boston]

I don't think 87/287 were meant to be separate, so probably shouldn't count that.  I'd also use a more appropriate term than "incest".  Perhaps "conjoined"?

I'm too lazy to look up how long it lasted (or even if they were even signed as such) but I do know that New York submitted two different numbers to AASHO for each of the two independent portions.

The Cross-Westchester Expressway was originally numbered I-487. New York for whatever reason wanted it to be a single route with the 287 in New Jersey, and it made sense to combine them over I-87 into one route.

I think it's the reverse: NY wanted I-487 for the Cross-Westchester and I-287 for NJ, but the FHWA or AASHTO wanted them combined.  This is due to the thought difference in what I-287 is: to those of us from upstate NY, it is two separate entities not at all related, a bypass of the Cross-Bronx, and a bypass of the Turnpike.  To everyone else, however, it's a beltway around NYC.

It's a bypass of the Cross-Bronx, and a bypass of the Turnpike, and a bypass of 80, and a bypass of 78...

A beltway is a connected continuum of bypasses.  Sometimes you have to turn off the states. 

[Zzonkmiles]

Coastal area traffic funnel: I-526 (SC), I-516 (GA)

It would be more accurate to call these traffic deltas as they divert a large amount of beach-bound traffic around the coastal city. I-140 and possibly I-664 would also fit into this category.

Fair point. I was thinking more of the opposite-direction traffic flow with these 3dis collecting (funneling) traffic from the coastal suburbs onto the main 2di (in these cases, I-26 and I-16). You are talking about traffic going from the 2di to the 3di, which is entirely valid.

[cjk374]

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

Especially I-H3, which shares a distinction with I-781 as ending directly at the entrance to a military facility (both I-H2 and I-564 end near such facilities, but directly at the gate).

And I-185 in GA should go into this category as well.

The freeway extends into Fort Benning, but I-185 itself doesn't...it ends at the 27/280 interchange.  Whereas 781 and H3 end almost literally at the base gate.

This is what LaDOTD has planned for I-220' eastern end.  They want to build the interstate onto Barksdale AFB property (which is the reason why I-220 will never be a full loop around Shreveport/ Bossier City) and build a new gate onto the base.

[logan230]

WV's only 3di is a bypass of Wheeling (I-470).

[odditude]

I-195 in NJ:  Double spur, leading to a "beltway" in one direction (I-295) and a toll road (GSP) in the other

I-195 was designed as a spur off of I-295. The Turnpike being redesignated at I-95 is just coincidence.

[TheStranger]

Those routes are actually usually comparable in time (I take both often).

Okay, I'll take your word for it.  CA 1 is prettier and less annoying though.

If you're referring to the Junipero Serra Freeway/19th Avenue/Park Presidio Boulevard section of Route 1 (between 280 and the Presidio)...other than Golden Gate Park, I don't think there's much scenic on that side, while US 101 passes right by City Hall and provides Presidio access that 1 doesn't.

(As Andy noted, 380-280-1 is generally the shorter route...though traffic on 19th CAN be as much of a factor as traffic along Van Ness/Lombard.  The latter though contains a lot of outbound/inbound commuters heading into downtown.)

[hbelkins]

The late I-181 in Tennessee was a double spur.

[cwf1701]

Anyone mentioned the international spurs yet? (i.e I-190 in NY, I-110 in Texas, I-375 in MI (ends near the Detroit-Windsor Tunnel), and Future I-905 in CA.

[empirestate]

Anyone mentioned the international spurs yet? (i.e I-190 in NY, I-110 in Texas, I-375 in MI (ends near the Detroit-Windsor Tunnel), and Future I-905 in CA.

That sort of occurred to me, but I wasn't sure whether it should constitute its own category, or just be a subset of other types (downtown spur, facility spur, etc.).