"Century" Multiplexes - Interstate and US Routes that add up to 100

[westerninterloper]

On a recent drive from Ohio to South Carolina, I began noticing how multiplexed Interstate and US highway routes often have complementary numbers that usually add up to between 90-110, but sometimes settle right on 100.

For example:
In NC, I-77 and US 21 = 98
In NC, I-85 and US 15 are multiplexed near Raleigh = 100
In KY, I-75 and US 25 share a bridge south of Lexington = 100

In OH, I-76 and US 224= 300
OH, I-475 + US 23 = 498

These are just a few of many. Do you know any multiplexed "century" routes?

[Bruce]

A long time ago: US 10 and I-90.

BC 99 and BC 1 (TCH) in North Vancouver.

WA has a lot of missing 2dis (from 41 onwards), so it's really hard to find century multiplexes. Adding up to 1,000 could be possible.

[Darkchylde]

I-20 and US 80, along with I-10 and US 90.

[Charles2]

Alabama and Mississippi: I-22 and US 78

[roadman65]

I-69 and US 31 once the NAFTA interstate gets signed along the I-465 Beltway.

[nexus73]

We need an I(minus)-1 on the Oregon Coast to go with US 101...LOL!  I guess we'll build it offshore.

Rick

[kj3400]

I-97 and BUS MD 3. Took me some head scratching to come up with that one.

[peterj920]

Wisconsin: I-39/U.S. 10/U.S. 51 in the Stevens Point Area for a triplex that equals 100

[national highway 1]

Alabama and Mississippi: I-22 and US 78

I-78 and US 22 in Pennsylvania.
Also a former multiplex- I-35 and US 65 in Minnesota between St Paul and Albert Lea.

[Rothman]

I-91 and US 5...almost.

[theline]

I-69 and US 31 once the NAFTA interstate gets signed along the I-465 Beltway.

Of course that's cherry picking just 2 routes from a multi-multiplex. I wonder what the maximum "total" is (will be) for any stretch of 465. INDOT piggybacks a lot of highways on the outer belt. I'm betting it's in the 700 or 800 range. Maybe I'll get time later to figure it out.

[Mapmikey]

I-85 and US 15

Honorable mention: I-40 Bus and US 60

Former: I-75 and US 25

Then there's I-70 and US 30 in Breezewood

Mike

[SD Mapman]

I-29 and US 71.

[spooky]

I-26 and US 74 in western North Carolina.

[NWI_Irish96]

US 6 and I-94 in IN/IL.  I believe that 6 is the lowest numbered US Route to have a "century multiplex"

[noelbotevera]

US 6 and I-94 in IN/IL.  I believe that 6 is the lowest numbered US Route to have a "century multiplex"

Yep.

[Kacie Jane]

WA has a lot of missing 2dis (from 41 onwards), so it's really hard to find century multiplexes. Adding up to 1,000 could be possible.

Nope.  You actually run into the same problem.  Lots of numbers in the lower half of each hundred, not so many in the upper half.  And when you do have more "upper half" numbers in the 100s and 200s, you have very few corresponding numbers in the 700s and 800s.

I think the only current pair that adds up to 1,000 is 401 and 599.  Which are pretty far from each other geographically.

Historically, there was an SR 294 outside Spokane until the 70s, but that's even further from SR 706.  Also, for a couple of years in the 60s, you could have paired 169/831 and 167/833.  But those were still separated by 100+ miles.

Back on topic, there are actually more existing century pairs than "millenium" pairs in Washington, but again no multiplexes.  SR 18/I-82, SR 10/I-90, SR 8/SR 92, SR 4/SR 96, and SR 3/US 97.  10/90 is obviously the closest, but SR 10 ends just short of I-90 on each side, so they don't even intersect, much less intersect.

ETA: I forgot to account for numbers ≤100 when looking for "millenium" pairs.  SR 900/SR 100 and SR 903/US 97 exist, as well as three more historical pairs.  Still no intersections or multiplexes, but at least 903 and 97 are both in the same part of the state.

[TheHighwayMan3561]

I-35 and US 65 formerly did before 65 was eliminated north of Albert Lea, MN.

[vtk]

Then there's I-70 and US 30 in Breezewood

Mike

Technically I-70 is discontinuous, so no.

Also, the 2dI+2dUS examples are boring.

[national highway 1]

I-35 and US 65 formerly did before 65 was eliminated north of Albert Lea, MN.

Already said that.

Alabama and Mississippi: I-22 and US 78

I-78 and US 22 in Pennsylvania.
Also a former multiplex- I-35 and US 65 in Minnesota between St Paul and Albert Lea.

[rlb2024]

I-30 and US 70 near Little Rock, AR.

[ModernDayWarrior]

Missouri: I-29 and US 71, from the KC metro to St. Joseph.

[TheHighwayMan3561]

I-35 and US 65 formerly did before 65 was eliminated north of Albert Lea, MN.

Already said that.

Alabama and Mississippi: I-22 and US 78

I-78 and US 22 in Pennsylvania.
Also a former multiplex- I-35 and US 65 in Minnesota between St Paul and Albert Lea.

Don't really care. Does it really need to be pointed out that I repeat posted?

[Road Hog]

Since Interstate numbers and US numbers are sequenced in opposite directions (from north to south and east to west), it's probably not too uncommon to see multiplexes that add up anywhere you look close to 100, anyway.

[westerninterloper]

Thanks everyone - I was aware of the contrasting numbering for US and Interstate routes, and I figured a lot of  x5 and x0 routes would add up to 100 - what surprises me are the other examples, and not just in a diagonal path from NE to SW across the country.