For each state, what is the most important route that never enters it?

[hotdogPi]

MA: My choice would be CT 20. It's an airport connector for an airport that serves the Springfield area.
NH: I would actually choose I-495 (MA) over I-91, as the I-495 area is much more populated.
ME: NB 2. (NH 16 enters ME.)
RI: I-395, maybe? It's in the less populated part of the state, but there aren't really any good choices in the Providence area.
CT: Complete guess, but NY 22. (People going to Six Flags from Connecticut will be using CT/MA 159, not MA 57.)
VT: A-35 until it gets completed to I-89. Once it does, still A-35 if it's considered a separate route, or NY 22 if A-35/I-89 and A-55/I-91 are each one route.

[NWI_Irish96]

This is a weird question, but for Indiana I'd have to say I-294.

[Max Rockatansky]

I-19 for California given a lot of people and freight cross the border there to Sonora.

[EpicRoadways]

For Minnesota, maybe WI-35? A decent number of people from River Falls and Hudson commute to the east metro so that would be my nomination. Otherwise you could maybe make a case for I-29 since it runs so close to the border although I don't think the majority of that traffic is Minnesota-bound, even in the Fargo and Grand Forks areas.

[Crown Victoria]

For PA, the New Jersey Turnpike mainline. It is the main route for traffic from NYC and New England to travel south and links to the only roadway that bypasses PA entirely (Delaware Memorial Bridge).

*The NJ Turnpike counts despite also carrying I-95 (which enters PA) because only part of the Turnpike is I-95. If one wishes we can consider the unsigned NJ 700 portion of the Turnpike as the "most important route".

[CNGL-Leudimin]

One that is outside an entire country, but still is important for it: Swiss A13 for Liechtenstein.

[Flint1979]

For Michigan I'll say probably US-20 or I-80/90.

[SkyPesos]

I'll go with I-65 for Ohio. Until I-69 is finished in KY and TN, which then the WK Parkway/I-71 can serve as a spur of I-69 into Ohio, I-65 is part of the fastest route from at least Cincinnati, Columbus and Cleveland via I-71 to cities in the south like Houston (I-71/I-65/I-40/I-30/US 59), Dallas (I-71/I-65/I-40/I-30), Austin/San Antonio (I-71/I-65/I-40/I-30/I-35) and New Orleans (I-71/I-65/I-59) and points beyond like Mexico or closer points like Memphis or Nashville. I-65 is also part of the fastest route from Cincinnati, Dayton and Columbus to Chicago and Milwaukee, and part of one of 2 options (along with I-74/I-39) to Madison and the Twin Cities.

Conversely, I think it might be I-75 for Indiana

For Missouri, this one is easy: I-24. Primary connector from most of the state, including St. Louis and Kansas City to the southeast.

[jp the roadgeek]

MA: My choice would be CT 20. It's an airport connector for an airport that serves the Springfield area.
NH: I would actually choose I-495 (MA) over I-91, as the I-495 area is much more populated.
ME: NB 2. (NH 16 enters ME.)
RI: I-395, maybe? It's in the less populated part of the state, but there aren't really any good choices in the Providence area.
CT: Complete guess, but NY 22. (People going to Six Flags from Connecticut will be using CT/MA 159, not MA 57.)
VT: A-35 until it gets completed to I-89. Once it does, still A-35 if it's considered a separate route, or NY 22 if A-35/I-89 and A-55/I-91 are each one route.

A couple others I'd consider

VT: MA 2 or I-87.  Many Bostonians would use MA 2 to get to area in southern VT.  Many New Yorkers use the Northway as long as possible before jumping east into VT because of a lack of major interstate south and west of Burlington.

RI: I-495.  A lot of traffic from the eastern part of the Worcester area and the outer parts of MetroWest will use it to get to the Providence area instead of MA/RI 146 or I-95.

CT: I'd have to say I-90.  It's a major part of the route from either Boston or Albany.  Every major numbered route coming from NYC enters the state. 

[thspfc]

Cool thread idea. I'd say I-80 for Wisconsin. You could also argue for IL I-290/294.

[Henry]

For WA, I'd say I-84, since that's a major part of a Salt Lake-Seattle route.

[1995hoo]

Virginia is tough. Given the layout of state lines, most of the significant routes in neighboring states or jurisdictions either pass through Virginia (US-50, I-64, I-95, I-81), don't come close enough to be a serious contender (see below about I-40), or just plain don't seem important enough in the big picture (I-83, North Carolina's I-73 and I-74). I-79 might fall into both of the latter categories.

For that reason, I'm inclined to say I-70. It passes within about 13 miles of Virginia (via US-340 and US-15) in the Frederick area–probably a bit less as the crow flies, but I don't have a good way to measure that–and it's the major route west for a lot of traffic because of people's bias against using non-Interstate routes.

I thought about I-40, but I don't think it passes close enough to Virginia to be a serious contender unless maybe you were to argue that it should have been routed northeast from Raleigh to Norfolk instead of southeast to Wilmington. I'd suggest the latter is more in the nature of "Fictional Highways" because for purposes of this thread, I figure we should take the highways as they are instead of saying "what if." That is, it's one thing if a route extension is planned, like the Autoroute 35 example in the original post, but it seems to me that if a totally different highway is planned in the future, that's a different matter that, for purposes of this thread, doesn't seem to justify saying (in this example) "I-40 should have gone there in the first place."

[corco]

Idaho is probably US 395 - since it forms part of the I-84/I-82/US 395/I-90 detour that is typically the fastest way from Boise to Coeur d'Alene in the winter.

I'm pretty sure Montana straight up doesn't have one - unless you count Alberta 4 (which turns into I-15).

Colorado is almost certainly I-80.

[jmacswimmer]

A couple options I can think of for Maryland:

-Delaware's iterations of I-295 (and by extension, the NJTP) & I-495, as they divide up the NYC/Philly traffic coming up the I-95 corridor from DC/Baltimore.

-I-76/PATP, as long-haul traffic heading west from DC/Baltimore toward Pittsburgh/Cleveland/Chicago enters the Turnpike at Breezewood.  This one ties in nicely with 1995hoo's comment on I-70 being the one for Virginia.  (On a more local level, I'd also include I-270 for Virginia, given how much traffic goes over the Legion Bridge on the beltway and then continues up I-270.)

[SP Cook]

WV is easy.  I-95.  The majority of what the government calls "tourists" are through tourists, and 90-79-L-77-26-95 is the direct drive from Toronto-Buffalo-Pittsburgh to Florida, and 77-26-95 is an even choice for Florida bound Clevelanders. 

Most of the trucking is likewise stuff coming out of the Midwest and heading to the coast. 

I-95.

[The Nature Boy]

MA: My choice would be CT 20. It's an airport connector for an airport that serves the Springfield area.
NH: I would actually choose I-495 (MA) over I-91, as the I-495 area is much more populated.
ME: NB 2. (NH 16 enters ME.)
RI: I-395, maybe? It's in the less populated part of the state, but there aren't really any good choices in the Providence area.
CT: Complete guess, but NY 22. (People going to Six Flags from Connecticut will be using CT/MA 159, not MA 57.)
VT: A-35 until it gets completed to I-89. Once it does, still A-35 if it's considered a separate route, or NY 22 if A-35/I-89 and A-55/I-91 are each one route.

I would disagree on I-495 for NH. In terms of importance to intrastate travel and commerce, I-91 trumps it. I-91 is a legitimate connector for NH towns in the Connecticut River Valley. A person traveling from Lebanon to Keene would take I-91 for most of the trip. Going north-south in that region of the state basically requires you to use I-91, which is fairly unique. It's a Vermont interstate that is the primary connection for an entire region of New Hampshire but yet never actually crosses into the state.

[SkyPesos]

For that reason, I'm inclined to say I-70. It passes within about 13 miles of Virginia (via US-340 and US-15) in the Frederick area—probably a bit less as the crow flies, but I don't have a good way to measure that—and it's the major route west for a lot of traffic because of people's bias against using non-Interstate routes.

Specifically for the DC/NoVA area, I-70 is pretty much the one choice. It's the main route going west of the area, even over I-66. Even for cities on I-64, like Louisville, to DC, the fastest route (I-64/I-79/I-68/I-70/I-270/I-495) uses I-70 into the area instead of I-66. I-70 also connects that area to cities on I-80/90 in the midwest like Chicago and Cleveland via I-76. It's not until cities on the I-40 corridor where I-66 becomes the clear winner over I-70 for route west of DC.

Could also mention I-270 for the US 15 connection in addition to I-70, which connects DC/NoVA to Upstate NY and Ontario.

[hbelkins]

Three choices I can think of for Kentucky: US 58, I-79, or I-81.

[1995hoo]

For that reason, I'm inclined to say I-70. It passes within about 13 miles of Virginia (via US-340 and US-15) in the Frederick area–probably a bit less as the crow flies, but I don't have a good way to measure that–and it's the major route west for a lot of traffic because of people's bias against using non-Interstate routes.

Specifically for the DC/NoVA area, I-70 is pretty much the one choice. It's the main route going west of the area, even over I-66. Even for cities on I-64, like Louisville, to DC, the fastest route (I-64/I-79/I-68/I-70/I-270/I-495) uses I-70 into the area instead of I-66. I-70 also connects that area to cities on I-80/90 in the midwest like Chicago and Cleveland via I-76. It's not until cities on the I-40 corridor where I-66 becomes the clear winner over I-70 for route west of DC.

Could also mention I-270 for the US 15 connection in addition to I-70, which connects DC/NoVA to Upstate NY and Ontario.

Heh, my wife was quite surprised and puzzled in October when I exited the Beltway onto westbound I-66 en route to Dayton. I intended to (and did) take Corridor H. She was thinking in terms of the Interstate route she had always taken (recognizing, to be fair, that for most of those years Corridor H either didn't exist or wasn't completed enough to be viable).

I thought about I-270, but I thought it kind of felt a lot like it's a continuous route with the Beltway in some respects. Of course it isn't really, but with the way the roads are configured, the Beltway to I-270 up to Frederick is a fairly natural route to take, and it's really at that point when you have to decide what to do (leave the Interstate for US-15 north, take I-70 to continue west, possibly take US-340 towards West Virginia).

Also, to be clear, while I-70 is not a road people from Richmond or Hampton Roads or Southwest Virginia would be using, I couldn't come up with any route of comparable significance in another state that would apply to those areas. That is, from Richmond if you were headed to Louisville (or Dayton, to use my example above) you'd likely take I-64 (and then US-35 in the Dayton example), but I-64 obviously enters Virginia. For Southwest Virginia, while I-26 crossed my mind, it just didn't seem as important on a national scale as I-70.

[SkyPesos]

For that reason, I'm inclined to say I-70. It passes within about 13 miles of Virginia (via US-340 and US-15) in the Frederick area—probably a bit less as the crow flies, but I don't have a good way to measure that—and it's the major route west for a lot of traffic because of people's bias against using non-Interstate routes.

Specifically for the DC/NoVA area, I-70 is pretty much the one choice. It's the main route going west of the area, even over I-66. Even for cities on I-64, like Louisville, to DC, the fastest route (I-64/I-79/I-68/I-70/I-270/I-495) uses I-70 into the area instead of I-66. I-70 also connects that area to cities on I-80/90 in the midwest like Chicago and Cleveland via I-76. It's not until cities on the I-40 corridor where I-66 becomes the clear winner over I-70 for route west of DC.

Could also mention I-270 for the US 15 connection in addition to I-70, which connects DC/NoVA to Upstate NY and Ontario.

I thought about I-270, but I thought it kind of felt a lot like it's a continuous route with the Beltway in some respects. Of course it isn't really, but with the way the roads are configured, the Beltway to I-270 up to Frederick is a fairly natural route to take, and it's really at that point when you have to decide what to do (leave the Interstate for US-15 north, take I-70 to continue west, possibly take US-340 towards West Virginia).

I also skipped out I-270 when going through this the first time because in my mindset, it's still I-70S, one of the very few removed suffixed interstates that makes sense to me, along with I-70N to Baltimore, because it's one of two branches serving the 2 principal cities of the combined DC-Baltimore metro area, similar to I-35 E/W for Dallas-Ft Worth and Minneapolis-St. Paul. Then there's the debate of how suffixed interstates should be counted, and for me, I count all 3 under I-70.

And then I realized that I-70S has been I-270 for the past 45 years

[Ben114]

CT: I'd have to say I-90.  It's a major part of the route from either Boston or Albany.  Every major numbered route coming from NYC enters the state.

Either this or I-87 for CT.

[US 89]

I don't think Utah really has one, since most long-distance corridors you'd take to get places from Utah pass through it. Maybe US 30 or 93, but really those are more useful for people in the small towns along them to get to Salt Lake rather than the other way around. Plus 30 isn't really that important of a route since it largely follows I-80 and I-84.

US 550 might be another option, since that's a big part of going SE from Salt Lake to really anywhere in the US south of I-40 and west of I-65.

[1995hoo]

I don't think Utah really has one, since most long-distance corridors you'd take to get places from Utah pass through it. Maybe US 30 or 93, but really those are more useful for people in the small towns along them to get to Salt Lake rather than the other way around. Plus 30 isn't really that important of a route since it largely follows I-80 and I-84.

US 550 might be another option, since that's a big part of going SE from Salt Lake to really anywhere in the US south of I-40 and west of I-65.

Maybe US-64? I recognize the part of Utah near there is relatively isolated from the rest of the state, of course.

[vdeane]

For NY, I-80 and the QEW.

[TXtoNJ]

For Texas, oddly enough, I'd say I-81. It's the only route that connects to all parts of the Triangle equally, far away as it is.

I-59 is more important for the southern parts of the Triangle, but Metroplex traffic has almost no reason to use it.

On second thought, I suppose I-12 is important for all parts of Texas going to the Florida Panhandle beaches, depending on whether Metroplex traffic uses I-49 to cut down, or cuts through Hattiesburg instead.