Longest highways without a single concurrency

[Bruce]

Curious to know what highways (either within a single state or spanning multiple) qualify.

For Washington, the winner is US 101, which clocks in at 366 miles and does not share an inch of asphalt with another route (though with one-way streets it technically might).

[Flint1979]

For a Michigan state highway it's M-57.
For US highways it's US-24.
For Interstate highways it's I-696.

[NWI_Irish96]

For Indiana:

Overall it's I-64 at 123 miles
For US highways, all of them except for the 0.64 miles of US 131 have concurrencies.
For state highways, the longest I can find is the northern segment of IN 63 at 63 miles.

[JayhawkCO]

Colorado
Interstate: I-225 - 12 Miles (the only one)
U.S. Highway: US350 - 72 miles
State Highway: CO149 - 118 miles

Wyoming
Interstate: None
U.S. Highway: None
State Highway: WYO28 - 96 miles

[SectorZ]

Massachusetts I believe would be I-90. MA 28 and US 20 are the only things longer and they have concurrencies with tons of things.

New Hampshire (and I had to look this up to confirm) is NH 175, just over 25 miles by itself. NH 110 is just behind it a half mile shorter.

[oscar]

In Alaska, AK 2 has no concurrencies (except with unsigned Interstates) for its entire ~445-mile length. Ditto AK 11, for its entire 416-mile length, except with no paper-Interstate concurrencies.

In the Northwest Territories, NT 1 has no concurrencies for its entire ~430-mile length (including two ferry crossings).

[hotdogPi]

Are double concurrencies allowed?

[Max Rockatansky]

Fairly certain it's CA 96 for California at 147 miles.

[bassoon1986]

Louisiana:

Interstate: I-12, 86 miles
US Route: none. US 65 is probably closest, just 2 small concurrencies
State Route: will take some research. There's lots of concurrencies


iPhone

[JayhawkCO]

Louisiana:

Interstate: I-12, 86 miles
US Route: none. US 65 is probably closest, just 2 small concurrencies
State Route: will take some research. There's lots of concurrencies


iPhone

Not to steal your thunder, but looks like LA77 at 49.2 miles.

[bassoon1986]

Louisiana:

Interstate: I-12, 86 miles
US Route: none. US 65 is probably closest, just 2 small concurrencies
State Route: will take some research. There's lots of concurrencies


iPhone

Not to steal your thunder, but looks like LA77 at 49.2 miles.

Nice! I really thought there might be one that broke 50 miles but like I said, Louisiana has lots of concurrencies. Even if it's just from a lot of zig-zag intersections where the other route crosses for a few blocks.


iPhone

[bassoon1986]

Louisiana:

Interstate: I-12, 86 miles
US Route: none. US 65 is probably closest, just 2 small concurrencies
State Route: will take some research. There's lots of concurrencies


iPhone

Not to steal your thunder, but looks like LA77 at 49.2 miles.

Nice! I really thought there might be one that broke 50 miles but like I said, Louisiana has lots of concurrencies. Even if it's just from a lot of zig-zag intersections where the other route crosses for a few blocks.


iPhone

LA 23 might count at 74 miles. Depends on if you call it a concurrency with Bus US 90. It stays on the frontage roads.


iPhone

[JayhawkCO]

Louisiana:

Interstate: I-12, 86 miles
US Route: none. US 65 is probably closest, just 2 small concurrencies
State Route: will take some research. There's lots of concurrencies


iPhone

Not to steal your thunder, but looks like LA77 at 49.2 miles.

Nice! I really thought there might be one that broke 50 miles but like I said, Louisiana has lots of concurrencies. Even if it's just from a lot of zig-zag intersections where the other route crosses for a few blocks.


iPhone

LA 23 might count at 74 miles. Depends on if you call it a concurrency with Bus US 90. It stays on the frontage roads.


iPhone

I looked at that briefly but just went by the Wikipedia article saying it was concurrent.  I didn't investigate too thoroughly.

[Bickendan]

For Oregon, it'll OR 127 by technicality - the ORH system overlaps every route, US highway, or Interstate save for a few routes without corresponding highways, like 132.
Without considering ORH, interstates still fail:
5 - 99, 138, 99E, 30
82 - 395
84 - 30, 395
105 - 126
205 - 213
405 - 26, 30

US:
20 - 34, 99W, 99E, 126, 97B, 395, 26, 201
26 - 47, 405, 97, 395, 20, 201
30 - 405, 5, 84, 35, 197, 37, 7
97 - 26
101 - passes
197 - 30, 216
395 - 82, 730, 84, 30, 26, 20, 140

OR:
31 stands out as the likely winner

[7/8]

For Ontario:
400-series Highways - The 417 at 192.0 km (119.3 mi) (third longest 400-series Highway)
King's Highways - Highway 144 at 271.7 km (168.8 mi) (sixth longest King's Highway)
Secondary Highways - Highway 599 at 291.0 km (180.8 mi) (also the longest Secondary Highway)
Tertiary Highways - Highway 811 at 59.0 km (36.7 mi) (also the longest Tertiary Highway)

[Bitmapped]

In West Virginia, the longest overlap-free route is WV 26 at 41.3 miles. Concurrency-free routings are fairly rate because of the terrain (hard to arrange things on grids like in states further west) and because of WV's propensity for trying to minimize the number of state route numbers at the cost of long distance multiplexes (see WV 28 as an example).

[jp the roadgeek]

CT:
Interstate: I-91 at 58 miles
US: All have concurrencies
State: CT 58 at 18.58 miles

[clong]

For Alabama:
I-10 @ 67 miles
US45 @ 59 miles
AL75 @ 115 miles

[KCRoadFan]

For US highways it's US-24.

I'm assuming you just mean within Michigan, right? Nationally, I know that right near where I live, US 24 is concurrent with US 40 between Lawrence, KS, and KC.

[SkyPesos]

Ohio

I - 270 (also one of the very few beltways that doesn't have any concurrencies)
US - None
SR - Too lazy to check all of them. Though of the routes I know of, 63 is the only one that doesn't have any concurrencies.

[hbelkins]

For Indiana:

Overall it's I-64 at 123 miles

Ahem...

2021 Western road trip Day 14 - 103 by H.B. Elkins, on Flickr

[JayhawkCO]

Ohio

I - 270 (also one of the very few beltways that doesn't have any concurrencies)
US - None
SR - Too lazy to check all of them. Though of the routes I know of, 63 is the only one that doesn't have any concurrencies.

Looks like OH534 at 69.41 miles.

[jmacswimmer]

Taking a swing at Maryland (credit to Wikipedia for some assistance):

Interstate: I-270 at 34 miles*
US: US 113 at 38 miles
State: MD 32 at 52 miles**

*If you discount the I-95/495 concurrency (I personally don't, but IIRC the I-495 designation was restored on the eastern half of the beltway for motorist convenience and may not have ever been officially restored per FHWA), then I-95 would take the title at 109 miles.  Additional sidenote: if you limit to 2di's and count the I-95/495 overlap, then I-97 would take the title in a somewhat ironic twist

**I originally thought it would be MD 213 at 68 miles, but Wikipedia indicates a one-way/one-block unsigned overlap between MD 213 NB & MD 304 WB in downtown Centreville in Queen Anne's County.

For US highways it's US-24.

I'm assuming you just mean within Michigan, right? Nationally, I know that right near where I live, US 24 is concurrent with US 40 between Lawrence, KS, and KC.

Off the top of my head, I also recall some overlaps with US 285 & I-25 when I was out in Colorado almost a year ago.

[TheHighwayMan3561]

MN

I-: none
US: none
MN: MN 61 (149 miles)

[JayhawkCO]

New Mexico
Interstate: None
US Highway: US82 - 193 miles
State Highway: NM120 - 119 miles (also the longest state highway)

Idaho
Interstate: I-90 - 74 miles
US Highway: US195 - 0.577 miles
State Highway: ID75 - 171 miles (also the longest state highway)