Concurrencies commonly called by both numbers

[fillup420]

For example: US 15 and US 501 run together for about 100 miles through NC. Many towns along the route refer to it as "15/501".

[amroad17]

I-71/75 in Northern Kentucky (71/75).  Also US 20/NY 5 in the Finger Lakes region of New York (20 and 5).

[jp the roadgeek]

US 1 & US 9 in NJ is called (The) 1 & 9 (NJDOT even puts the numbers on the same shield). 
CT 8 and CT 25 through Bridgeport is often called "The 8/25 connector"
US 202 and US 206 in NJ is referred to as Route 202/206.
In Providence, the US 6/RI 10 concurrency is called "The 6/10 freeway")

[briantroutman]

US 11-15 through the Central Susquehanna Valley is frequently called "eleven-fifteen"  by locals. I've also heard many people say "22-322"  in reference to the road through the Juniata Valley.

Rarely, I've heard "seventy-seventy-six"  in reference to the overlap between Breezewood and New Stanton, but "the Turnpike"  is far more common.

I know that the US 22-30 concurrency (along with I-376) is typically referred to as "Parkway East"  or "Parkway West"  depending on which side of Fort Pitt you're on, but what about the freeway that breaks off at Robinson toward Steubenville? Does anyone call that "twenty-two-thirty" ?

[epzik8]

I would say Maryland Route 2-4 through Calvert County, since they're both separate significant corridors north of Sunderland.

Conversely, U.S. 50/301 from Bowie to Queenstown (also secret I-595 from Bowie to somewhere in Annapolis) is usually just referred to as Route 50 since that's the route associated with the drive to Ocean City.

[machias]

In the Finger Lakes I'm pretty sure they called it "5 & 20", even though it's rightfully signed "20 & 5" (US 20 and NY 5).

[1995hoo]

When I was a kid, US-29 and US-211 ran together through Northern Virginia and it was common to hear people refer to "29/211," but since 211 was truncated to Warrenton that habit fell by the wayside years ago.

[jeffandnicole]

Sometimes they'll use 13 & 40 together in Delaware.

[dgolub]

NY 106/NY 107 on Long Island is generally called by both numbers.

[PHLBOS]

In MA, 4 & 225 (where they're concurrent) are called by both numbers.

[SP Cook]

Although it has not been US 21 for over three decades, and has not really bypassed town for longer than that, most oldtimers still call a road in Beckley WV "the 19-21 Bypass".

[MNHighwayMan]

I-35/80 in the Des Moines area is often referred to as "80/35." There's even a music festival that goes by that name.

[pianocello]

I-35/80 in the Des Moines area is often referred to as "80/35." There's even a music festival that goes by that name.

Correct me if I'm wrong, but I think the outer bypass of Des Moines is referred to as "65/5", despite the concurrency itself being only a mile or two.

Also, there's I-80/94 in Northwest Indiana

[hbelkins]

The most obvious example is in St. Louis. 64/40.

[DTComposer]

In Southern California, traffic reports commonly refer to the 57/60 and the 60/215.

Usually California doesn't do multiplexed routes, so the 60/215 is officially just I-215 (the definition of CA-60 has a break). However, the definitions of CA-60 and CA-57 don't have breaks, so they are technically multiplexed (although the bridge log and postmile services both list this segment as CA-60).

[MNHighwayMan]

I-35/80 in the Des Moines area is often referred to as "80/35." There's even a music festival that goes by that name.

Correct me if I'm wrong, but I think the outer bypass of Des Moines is referred to as "65/5", despite the concurrency itself being only a mile or two.

I personally have not ever heard that one. Usually I hear it just simply referred to as "the bypass" or the number of the section relevant to the conversation.

[JJBers]

US 5/CT 15 is sometimes used, but its mostly called Route 15.

[fillup420]

I-40/85 through central NC is referred to as such

[Brandon]

I-35/80 in the Des Moines area is often referred to as "80/35." There's even a music festival that goes by that name.

Correct me if I'm wrong, but I think the outer bypass of Des Moines is referred to as "65/5", despite the concurrency itself being only a mile or two.

Also, there's I-80/94 in Northwest Indiana

Yes, and there's 80/90 as well.  Both also have names that get used 80/94 is "The Borman", and 80/90 is the "Indiana Toll Road" and "Ohio Turnpike".  However, on Chicago radio, 80/94 is usually called that, and 80/90 is "The Toll Road" or "Indiana Toll Road".

[TheHighwayMan3561]

The I-94/694 concurrency in the northwest part of the Twin Cities is referred to as 94/694 by many. This is not the case for I-494/MN 5, however.

[Eth]

I-75/85 through downtown Atlanta. Also "19/41" for the US routes from Atlanta down to Griffin.

[lepidopteran]

In Idaho Springs, Colorado, there's the "6 & 40 Motel", named for the respective US routes.  Not sure if that's what the road was referred to, though.  Nowadays, both routes appear to be part of I-70 at that point.
https://commons.wikimedia.org/wiki/File:6%2640_Motel_sign,_Idaho_Springs.jpg

In upstate New York, US-44 and State Route 55 run concurrently for a ways west of Poughkeepsie.  Once or twice I heard that called 44-55.

Between Culpeper and Gainesville, VA, US-15 and US-29 run concurrently.  Anyone know if this is ever called 15-29?

Someone else mentioned I-80 and I-90 in Indiana.  They are also concurrent for about 2/3 of their run through Ohio.  However, I've only ever heard that called the Ohio Turnpike.

A very long time ago (over 35 years), I read a newspaper article that I think was about a trend, at the time, of people posting public apologies for road-rage behaviors (!).  The example was given was out of Chicago, where a woman wrote that she was really sorry about what she did on "80-90-94" the other day.  Was there ever a time when all 3 routes were on the same highway?  Note that it was not a Chicago newspaper where I read this.

[corco]

US 20/26 through Boise is typically referred to as such when it is not referred to by the local street name.

[Takumi]

I've heard the 1/301 overlap between Richmond and Petersburg called by each number, but rarely if ever both.

[ilpt4u]

The most obvious example is in St. Louis. 64/40.

I would dispute that -- at least my time spent in STL, many Locals simply refer to it still as 40