Interstates and US routes w/o a duplex within a state

[golden eagle]

In Mississippi, I-10, I-110 and US 90 along the Gulf Coast are not duplexed with any other highways. In the northern part, US 72 and 78 are by their lonesome, though 78 will become I-22 in the very near future.

[hotdogPi]

I-91 in Vermont.

Plus many short ones (most 3dis that are 10 miles or shorter would qualify).

[GaryV]

In Michigan:

I-475 and I-675
US-45 and US-8

[roadman65]

In Florida I-4 does not at all duplex with any routes.

Also I-75, I-175, I-375, I-295, I-595, and I-110.

[froggie]

I-91 in Vermont.

Technically has TRUCK US 2 and TRUCK VT 9.

[NE2]

In Florida I-4 does not at all duplex with any routes.

Unless you count US 17-92 Truck. But truck routes usually live on a different plane.

[hbelkins]

Kentucky has four interstates without concurrencies.

I-24, I-264 (since US 60 was taken off the Watterson Expressway many years ago), I-275 and I-471.

I-64 enters the state with US 150. I-65 has a brief concurrency with KY 61 in Louisville in at least one direction. I-71 and I-75 have a concurrency. I-265 is also co-signed with KY 841.

Every US route has a concurrency, with the possible exception of US 79. It may have a short concurrency with a state route, but to confirm would require an inspection of Kentucky county route maps.

[NE2]

Every US route has a concurrency, with the possible exception of US 79. It may have a short concurrency with a state route, but to confirm would require an inspection of Kentucky county route maps.

KY 1151: http://en.wikipedia.org/wiki/U.S._Route_79_in_Kentucky#Major_intersections

[hotdogPi]

Is US 160 cheating?

[corco]

I-90, I-184, and US 195 are the only ones in Idaho.

Montana has none. Wyoming has US 212 and that's it.

[golden eagle]

I-85, 165 and 10 in Alabama made the cut. I-65 almost made it, but it has a short concurrency with US 82 in the Montgomery area.

[PHLBOS]

PA (off the top of my head)

I-95 (forgot about the short segment that duplexes w/US 322)
I-176
I-276
I-283
I-476
I-579

MA

I-84 (though it was once co-signed w/MA 15 many years back)
I-90
I-190
I-290
I-295
I-391
I-395

[Zeffy]

New Jersey:

I-195
I-287
I-76

US 322?

[PHLBOS]

US 322?

Nope, the eastern leg of it's duplexed (unnecessarily IMHO) with US 40.

[Ian]

I-195 in Saco/OOB is the only interstate in Maine without any duplexes if you don't count the Falmouth Spur (hidden I-495). All other US and interstates in the state have at least one duplex somewhere along their routes.

[bassoon1986]

Louisiana has:
I-12
I-110
I-210
I-220
I-610

All US routes are duplexed at some point. US 65 comes the closest. Only one short duplex with LA 128, and that looks like it could have been a realignment from meeting US 65 in the middle of a curve

[roadman65]

I-85, 165 and 10 in Alabama made the cut. I-65 almost made it, but it has a short concurrency with US 82 in the Montgomery area.

Also US 31 in two places.  One north of Birmingham and the other at the AL/TN State Line.

[froggie]

I-85, 165 and 10 in Alabama made the cut.

I-85 and US 80 are concurrent between Exit 11 and Exit 16.  Google Maps is in error here.

US 29 and US 280 also have concurrencies with I-85 in the Auburn/Opelika area.

Unless I'm missing something, I-459 is another Alabama route that lacks concurrencies.

[NE2]

I-165 overlaps US 90 and US 98 Truck.

[jwolfer]

In Florida I-4 does not at all duplex with any routes.

Also I-75, I-175, I-375, I-295, I-595, and I-110.

All Florida interstates are duplexed with the unsigned SR numbers. US 17 and SR228 triplex with I-10 and I-95 in downtown Jax.  And as far as I have read here US 1 and 90 triplex with I-95 in downtown Jacksonville

Although the only place you ever see secret SR number on interstates is the construction info signs

[jdb1234]

I-85 and US 80 are concurrent between Exit 11 and Exit 16.  Google Maps is in error here.

If I remember correctly, I-85 and US 80 are concurrent between Exit 6 and Exit 16. 

I-85, 165 and 10 in Alabama made the cut. I-65 almost made it, but it has a short concurrency with US 82 in the Montgomery area.

Also US 31 in two places.  One north of Birmingham and the other at the AL/TN State Line.

And AL 69 between Exits 299 and 304.

And US 80 between Exit 167 and 168.

[US81]

Texas loves to decommission and I may have missed something, but I don't find any US routes in Texas that don't duplex at some point. Regarding Interstates, I think I-610, I-635 and (arguably) I-345 may qualify.

[akotchi]

PA (off the top of my head)

I-95
I-176
I-276
I-283
I-476

I-95 has a short duplex with U.S. 322 between Exits 3 and 4.

[bulldog1979]

In Michigan:

I-475 and I-675
US-45 and US-8

Unless I missed something, I-375 and I-696 also lack concurrencies. Also, I don't think US 24 has a concurrency in Michigan at the present time.

[GaryV]

In Michigan:

I-475 and I-675
US-45 and US-8

Unless I missed something, I-375 and I-696 also lack concurrencies. Also, I don't think US 24 has a concurrency in Michigan at the present time.

Correct, I missed those.