Interstate/State Route Concurrencies

[Hoss6884]

I couldn't find that this topic has already been covered on the forum (apologies if it has been).

Interstate 77 and WV Route 2 are concurrent from Silverton to Parkersburg (about 34 miles).  I'm imagining that it is rather rare to have a concurrency that long with a state route.  Are there any other examples in the country like this?

[The Nature Boy]

How long (legally) is that I-95/Rt. 128 concurrency in the Boston area? That might be a contender.

[Mapmikey]

The winner will be I-86 and NY 17 at hundreds of miles.

Mapmikey

[Big John]

I assume you skip Georgia where every Interstate has a hidden State Route concurrency?

[ajlynch91]

I-290, I-88, I-172, and I-74 all are concurrent with IL-110.

[jp the roadgeek]

CT doesn't have a single instance (unless you believe CONNDOT, who put up CT 6 signs instead of US 6 in Farmington and West Hartford

[Mapmikey]

I assume you skip Georgia where every Interstate has a hidden State Route concurrency?

When fully finished I-86/NY 17 would be longer than the longest Georgia interstate (I-75) but still shorter than I-75 in Florida which also has secret state routes on its interstates.  But to be fair Georgia at least used to put the 4xx number in small numbers at the bottom of the interstate route mile markers...

Mapmikey

[Zeffy]

I can't think of a single instance in New Jersey, unless you want to count the Turnpike's hidden designation, which I'm pretty sure doesn't count.

[sandwalk]

Twice:

Ohio State Route 2 is concurrent with I-90 for about 17 miles in the western suburbs of Cleveland.  Then just east of downtown, Route 2 connects back up with I-90 for another 10 miles through the east side.

[kurumi]

CT doesn't have a single instance (unless you believe CONNDOT, who put up CT 6 signs instead of US 6 in Farmington and West Hartford

There is one tiny (0.52 mile) overlap, which the highway log confirms. Hint: the ratio of route numbers is 7:6.

[ajlynch91]

^I-84 and CT-72

[Kacie Jane]

I can't think of a single instance in New Jersey, unless you want to count the Turnpike's hidden designation, which I'm pretty sure doesn't count.

Which wouldn't even count if we were including hidden designations. The Turnpike is only 700 where it's not 95.

But you're forgetting the northernmost mile of I-287, concurrent with NJ 17.

[PHLBOS]

How long (legally) is that I-95/Rt. 128 concurrency in the Boston area? That might be a contender.

Just over 37 miles from Canton (Exit 12) to Peabody (Exit 45).

[roadman65]

I can't think of a single instance in New Jersey, unless you want to count the Turnpike's hidden designation, which I'm pretty sure doesn't count.

NJ 173 does near Clinton for a short stretch with I-78

[Darkchylde]

Not all of them are long, but here's a few Interstate/SR concurrencies I'm aware of.

I-510 and LA 47
I-49 and LA 28
I-49 and MO 7
I-49 and MO 52
I-470 and MO 291
I-635 and K-5
I-70 and K-4

[TheStranger]

California's state route/Interstate concurrencies:

Interstate 5
(former: Route 75 from Exit 3 in San Ysidro to Exit 5 near Imperial Beach)
(former: Route 134 from Exit 142 near Glendale to Exit 145B)
(former: Route 126 from Exit 170 in Santa Clarita to Exit 172)
Route 33 from Exit 337 north of Coalinga to Exit 349
Route 4 from Exit 471 in Stockton to Exit 472
[gap in Route 16 from Exit 518 in Sacramento to exit 541 in Woodland]
Route 99 from Exit 518 in Sacramento to Exit 525B
Route 113 from Exit 537 in Woodland to Exit 538
(former: Route 299 from Exit 678B in Redding to Exit 680)

unsigned Interstate 305
Route 99 [and gap in Route 16] from Exit 4 in Sacramento to Exit 6B
depending on FHWA definition...could also include Route 51 from Exit 6B in midtown Sacramento to Exit 7B

Interstate 405
Route 22 from Exit 21 in Seal Beach to Exit 23   

Interstate 8
(former: Route 67 from Exit 14C in La Mesa to Exit 17B in El Cajon)

Interstate 15
Route 79 from Exit 58 in Temecula to Exit 61
Route 18 from Exit 150 in Victorville to Exit 153A

Interstate 215
Route 74 from Exit 15 in Romoland to Exit 17 in Perris
Route 60 from Exit 29 in Moreno Valley to Exit 34B in Riverside

Interstate 80
(former: Route 17 from the Macarthur Maze in Oakland north to Exit 13B in Albany)
Route 12 from Exit 39B in Cordelia to Exit 43 in Fairfield
Route 113 from Exit 66 in Dixon to exit 70 in Davis
[gap in Route 193 from Exit 116 in Newcastle to Exit 119A in Auburn]
Route 89 from Exit 185 in Truckee to Exit 188B

Interstate 280
(former: Route 17 along today's 880 in San Jose (between 280 and 101))
(former: Route 85 from Exit 11 in Cupertino to Exit 12B)
Route 35 from Exit 34 in San Mateo to Exit 41 in San Bruno
Route 1 from Exit 47 in Daly City to Exit 49B (originally planned to continue into the SF Presidio)

Interstate 680
(former: Route 17 along today's 880 between 101 in San Jose and 262 in Fremont)
Route 84 (eastbound only) from northbound Exit 21A in Sunol to Exit 21B
(former: Route 24 from Exit 46A in Walnut Creek to Exit 50 in Concord)

Interstate 880
Route 84 from Exit 19 in Fremont to Exit 21

[akotchi]

I-81/PA 309 in the Wilkes Barre area, I-78/PA 309 in the Allentown area, and I-99/PA 26 in the Bellefonte area are a few that come to mind.

[Bickendan]

OR 99 has 85 miles with I-5, and adding OR 99E, it comes to 109 miles.

CA 99 pulls 7 miles with I-5, and 1 on US 50 (Bus I-80/I-305).
CA 16 unofficially clocks 23 miles on I-5 and 1 on Bus I-80/I-305 (and 8 on CA 99 and 3 on US 50), but officially it's discontinuous between both ends of the overlap.
CA 51 (completely unsigned) is with Bus I-80 for its entire 9 miles, with less than a mile with I-305.

California most likely has a few others scattered about (CA 35 and I-280?), but the Sacramento ones are the big ones.

[PHLBOS]

Aside from the fore-mentioned I-95/MA 128, here are a few other Interstate/State route concurrencies in the Bay State:

I-93 (O'Neill Tunnel & Southeast Expressway) w/MA 3 (& US 1)

I-495 & MA 140 in Mansfield (though 140 only runs along the C/D roads)

I-195 & MA 24 in Fall River

I-91 & MA 2 in Greenfield

[TheStranger]

CA 99 pulls 7 miles with I-5, and 1 on US 50 (Bus I-80/I-305).
CA 16 unofficially clocks 23 miles on I-5 and 1 on Bus I-80/I-305 (and 8 on CA 99 and 3 on US 50), but officially it's discontinuous between both ends of the overlap.
CA 51 (completely unsigned) is with Bus I-80 for its entire 9 miles, with less than a mile with I-305.

California most likely has a few others scattered about (CA 35 and I-280?), but the Sacramento ones are the big ones.

I think the longest might actually be the rather underwhelming Route 33/I-5 concurrency north of Coalinga, at 12 miles.

[TheHighwayMan3561]

Minnesota:

I-35/MN 23 (11 miles; 180-191)

I-90/MN 43 (3 miles; 249-252)

I-94/MN 55 (4 miles; 230-234)
I-94/MN 95 (5 miles; 253-258)
I-94/MN 210 (3 miles; 54-57)

I-494/MN 5 (10 miles; 1A-11C)

[Bickendan]

CA 99 pulls 7 miles with I-5, and 1 on US 50 (Bus I-80/I-305).
CA 16 unofficially clocks 23 miles on I-5 and 1 on Bus I-80/I-305 (and 8 on CA 99 and 3 on US 50), but officially it's discontinuous between both ends of the overlap.
CA 51 (completely unsigned) is with Bus I-80 for its entire 9 miles, with less than a mile with I-305.

California most likely has a few others scattered about (CA 35 and I-280?), but the Sacramento ones are the big ones.

I think the longest might actually be the rather underwhelming Route 33/I-5 concurrency north of Coalinga, at 12 miles.

That... sounds about right.

How about the US 101/CA 1 pairings?

[TheStranger]

CA 99 pulls 7 miles with I-5, and 1 on US 50 (Bus I-80/I-305).
CA 16 unofficially clocks 23 miles on I-5 and 1 on Bus I-80/I-305 (and 8 on CA 99 and 3 on US 50), but officially it's discontinuous between both ends of the overlap.
CA 51 (completely unsigned) is with Bus I-80 for its entire 9 miles, with less than a mile with I-305.

California most likely has a few others scattered about (CA 35 and I-280?), but the Sacramento ones are the big ones.

I think the longest might actually be the rather underwhelming Route 33/I-5 concurrency north of Coalinga, at 12 miles.

That... sounds about right.

How about the US 101/CA 1 pairings?

The segment of US 101/Route 1 from Hobson County Park west of Ventura (at US 101 Exit 78) to Gaviota (at US 101 Exit 132) might be the longest single concurrency in the state, 52.5 miles long.

Prior to 1981 (when Route 1 was given a standalone routing to Hobson County Park), the concurrency went even further east/south to Oxnard at US 101 Exit 62B, for a total of 68.9 miles.

Total length the two routes run together:

1. Oxnard to Ventura (Exit 72) - 10 miles
2. the aforementioned 52.5 mile Hobson County Park to Gaviota segment, 52.5 miles
3. Exit 191B in Pismo Beach to Exit 203A in San Luis Obispo, 12 miles
4. San Francisco Presidio at Exit 438 to Exit 445B in Sausalito, 5.8 miles

80.3 miles concurrent, previously 96.7 miles.

[WillWeaverRVA]

Virginia has a few of these. I-64 has a lengthy concurrency with VA 33, and shorter ones with VA 134 and VA 168. I-264 has a brief multiplex with VA 337, and I-66 has concurrencies with VA 55 and VA 234.

[sbeaver44]

I-81/PA 309 in the Wilkes Barre area, I-78/PA 309 in the Allentown area, and I-99/PA 26 in the Bellefonte area are a few that come to mind.

The I-99/US 220/PA 26 one is interesting...an Interstate/US Route/State Route concurrency.  I-90/US 14/SD 79 listed below also meets that test, as does I-86/US 219/NY 17 (with the 86/17 mentioned previously)

Adding more PA to this:
-I-80/PA 66 near Clarion

More New York:
-I-81/NY 17 in Binghamton
-I-84/NY 52 near Newburgh
-I-88/NY 7 near Binghamton
-I-87/NY 7 near Albany (North 87 only)
-I-790/NY 5-8-12 in Utica
-I-88/NY 28 in Oneonta
-I-190/NY 324 over the South Grand Island Bridge
-I-278/NY 440 in Staten Island
-NOT NY 15 - Officially begins in Wayland despite signage that NY seems to keep putting up  (Why doesn't NY just make NY 415 into NY 15?)
-Does NY 878/I-878 count? 

Maryland and Delaware don't seem to have anything.

South Dakota I-90:
-With SD 34 from Exits 23-30 (Sturgis)
-With SD 79 from Exits 30-61 (Sturgis-Rapid City) (The way this has changed over time confuses me)
-With SD 73 from Exits 143-150 (Kadoka)
-With SD 63 from Exits 163-170 (Belvidere)
-With SD 50 from Exits 265-272 (Chamberlain)
-With SD 45 from Exits 284-289 (Kimball)
-With SD 37 from Exits 330-332 (Mitchell)
-NOT SD 47 - Runs Parallel