The most/least vital Interstate to the US as a whole

[DTComposer]

So I'm using just population numbers to start with: number of CSA/MSAs over 500,000 that an Interstate goes through, and the aggregate population thereof. For east-west routes, I included any x0 routes, plus any routes that were longer than the shortest x0 route.

East-West:
I-80 - 13 areas - 55,502,027
I-10 - 11 areas - 39,242,214
I-90 - 12 areas - 33,119,335
I-40 - 9 areas - 30,119,331*
I-70 - 8 areas - 26,697, 891
I-94 - 7 areas - 23,234,249
I-20 - 6 areas - 17,110,159
I-76 - 6 areas - 15,748,368
I-30 - 2 areas - 8,255,056
I-64 - 5 areas - 7,084,259
I-84 - 3 areas - 6,227,701
I-44 - 4 areas - 5,996,415

*I-40 includes the Los Angeles CSA, which it does run through, albeit far removed from the actual urbanized area. Leave L.A. off and it drops down to 11,569,043

I could agree about the order of the top three and the bottom three; the middle six have more room for argument in their order.

[Bickendan]

Least important: I'll note the thread doesn't specifically rule out 3DIs, so IL I-180 ("E/W") and MT I-315 ("N/S")

Problem is, I-180 in Illinois is signed north-south, not east-west.

Hence the quote marks

[tidecat]

I would go with I-40 for the most vital East/West route, simply because some of the places it goes through are critically important to logistics in this country.

For the least vital East/West route I would go with I-2 simply because it is the newest addition and serves a very limited area. If I-2 connected to I-35 I would probably go with I-86 in Idaho.

On the North-South side I would go with I-97 for the least important because of how short it is, even if it does connect to a state capital.  I would go with I-35 for the most important due to its combination of populous cities served and importance to the movement of freight.

[Quillz]

I-97 and I-99 seem the least vital to me.

The former is 17 miles and could easily have remained a state highway. The latter is entirely co-signed with US-220 (for now) and could have remained as such.

[jakeroot]

I would say that most of the interstates out west are more important than ones back east. Much of the west has thrived since they were constructed -- if they suddenly disappeared tomorrow, lots of cities would be very unreasonably disconnected.

Above all, I think I-5 is most vital. It is the only interstate connecting Mexico with Canada, and has very few bypasses, to the point that if it were not there (and neither was US-99), I have literally no idea how I'd get to Portland, much less California.

Least vital...hmm. Not sure there is one. Most interstate highways connect important places (if they didn't, they probably wouldn't have gotten the designation to begin with [though that is certainly debatable, though it's a debate I'd prefer to not discuss]).

[corco]

Least important: I'll note the thread doesn't specifically rule out 3DIs, so IL I-180 ("E/W") and MT I-315 ("N/S")

Problem is, I-180 in Illinois is signed north-south, not east-west.

315 isn't signed, but is more east-west than it is north-south, so maybe he could get away with just switching them.

(Although the three routes that are signed the length of 315 are all north-south.... Although two of them are north-south and one is south-north....)

And Montana 200 is east-west.

[Scott5114]

E-W is tough, as these routes have a lot of isolation in the western states.  I might argue for I-70 here, just because of its central location.

I-70 has the disadvantages of running out at Cove Fort (so you have to use another Interstate to access California or Nevada) and running through a lot of high-elevation territory in Utah and Colorado that is prone to snow. Both I-40 and I-80 are better options unless you need to go to Denver. East of about Kansas City, I-70 is a more reasonable option.

[Pink Jazz]

I would go with I-95 for N/S and I-80 for E/W as the most important.  For the least important for all directions would be the Hawaii Interstates.

[SP Cook]

I would say that in terms of commerce, it is hard to argue with I-81, followed by I-35 and I-75 are the most vital.  In terms of tourism and travel, I-95.  N-S routes are really way more important than E-W in general terms.  How many travelers, or trucks, really travel coast to coast? 

As to the least, I-68, followed by 99.  None go near anything important.

[kkt]

In the continuous 48 states,

Most:  another vote for I-95 and I-80

Least:  Idaho I-86, I-99

[TEG24601]

Most Vital - I would say...


N/S - I-5, I-35, I-95
E/W - I-90, I-80, I-40, I-10


Least Vital -


N/S - I-99, I-97, I-43, I-17, I-19, I-27
E/W - I-82(W), I-86 (W), I-88(C), I-96, I-72(C)

[Kacie Jane]

Least important: I'll note the thread doesn't specifically rule out 3DIs, so IL I-180 ("E/W") and MT I-315 ("N/S")

Problem is, I-180 in Illinois is signed north-south, not east-west.

315 isn't signed, but is more east-west than it is north-south, so maybe he could get away with just switching them.

(Although the three routes that are signed the length of 315 are all north-south.... Although two of them are north-south and one is south-north....)

And Montana 200 is east-west.

Oops... missed that one somehow... Just so I'm clear, since now I've confused myself...

If you're going compass east on I-315, you're going:
North on BL-15
South on US 89
South on MT 3
East on MT 200?

In addition to forgetting 200, I think I had one of those switched in my head, but since I didn't specify in my post, it didn't show...

[tribar]

Most Important East-West I-80, I-90, I-10
Most Important North-South I-5, I-95

Least Important East-West I-2 (Seriously, what purpose does this serve)
Least Important North-South I-180 (ILL)

[mrsman]

As far as the least vital:  I-180 in Wyoming.  It doesn't even meet basic criteria.

If we limit the discussion to 2 dis, I'd vote for I-97

If we limit the discussion to 2 dis that are more than 100 miles:  I-27

But I don't think it is fair to have any one highway being the most vital.  FDR had proposed a system of toll superhighways and even then he understood that to cover the breadth of the county, you need at least 3 N-S and 3 E-W.

With that, I'd say the most vital corridors are:

I-90/94/80 combo: Seattle - Billings - Minneapolis - Chicago - Cleveland - NYC
I-80/70 combo:  SF- Salt Lake - Denver - St Louis - Columbus - Pittsburgh - DC
I-10/20 combo: LA-Phoenix-Dallas-Atlanta-Savannah

Modified I-95:  Boston- NYC-DC-Raleigh-Charlotte-Jacksonville-Miami
I-55
I-5

[noelbotevera]

I would say that most of the interstates out west are more important than ones back east. Much of the west has thrived since they were constructed -- if they suddenly disappeared tomorrow, lots of cities would be very unreasonably disconnected.

Above all, I think I-5 is most vital. It is the only interstate connecting Mexico with Canada, and has very few bypasses, to the point that if it were not there (and neither was US-99), I have literally no idea how I'd get to Portland, much less California.

Least vital...hmm. Not sure there is one. Most interstate highways connect important places (if they didn't, they probably wouldn't have gotten the designation to begin with [though that is certainly debatable, though it's a debate I'd prefer to not discuss]).

Portland would be US 101 to US 26/US 30. At least you can get to California - the only city that would have a lack of a north-south route is Sacramento, but you can take I-80 to US 101. If you want a way into the Central Valley, you can use US 101 to CA 33 to CA 58 to CA 99.