Years ago, to the southwest of Atlanta's Hartsfield (today known as Hartsfield-Jackson) Airport, I-85 and I-285 were duplexed for a short stretch between the interchange where I-85 was routed to the inside of I-285 and the interchange where I-85 was routed to the outside of I-285. Later, the two intersections were combined, for lack of a better phrase, into a large "mega-interchange" (http://maps.google.com/maps?q=atlanta+ga&hl=en&ll=33.620266,-84.47422&spn=0.0223,0.038409&sll=37.0625,-95.677068&sspn=43.25835,78.662109&vpsrc=6&hnear=Atlanta,+Fulton,+Georgia&t=h&z=15) in which the duplex was eliminated and I-85 and I-285 maintain independent routings.
Two questions:
(1) What is the longest parallel, non-duplexed routing of two interstates in the interstate system (same question for freeways, too)?
(2) I referred to it as a "mega-interchange"; should the system in the link above properly be considered as one interchange or two interchanges?
Highway 401 Collectors and Highway 401 Express :)
I-295 and the New Jersey Turnpike run parallel for quite a distance between the Delaware Memorial Bridge and up to Trenton.
Quote from: PennDOTFan on January 22, 2012, 04:40:09 PM
I-295 and the New Jersey Turnpike run parallel for quite a distance between the Delaware Memorial Bridge and up to Trenton.
That's not the sort of parallel routes he's talking about though. He's talking about specifically where one freeway is sort of "inside" another -- the way the Garden State Parkway and US 9 are between Exits 127 and 129, or I-295 and I-76 where the latter ends and turns into NJ 42.
Or, as NE2 cheekily pointed out, similar to any local/express setup, or the NJTP's truck and car lanes... except with two different freeways involved.
Quote from: Grzrd on January 22, 2012, 04:09:08 PM
Years ago, to the southwest of Atlanta's Hartsfield (today known as Hartsfield-Jackson) Airport, I-85 and I-285 were duplexed for a short stretch between the interchange where I-85 was routed to the inside of I-285 and the interchange where I-85 was routed to the outside of I-285. Later, the two intersections were combined, for lack of a better phrase, into . . . a large "mega-interchange" in which the duplex was eliminated and I-85 and I-285 maintain independent routings.
Two questions:
(1) What is the longest parallel, non-duplexed routing of two interstates in the interstate system (same question for freeways, too)?
(2) I referred to it as a "mega-interchange"; should the system in the link above properly be considered as one interchange or two interchanges?
Isn't there a similar situation with I-90 and I-790 in Utica, NY? A little different in that I-790 ends in the interchange while I-85 & I-285 intersect and continue, but I-90 is "inside" of I-790 for some distance.
Had they built the I-271/I-480 duplex the way they could have, using what to this day is a wide median with ghost grading for lanes like the express lanes to the north on 271 (with overpasses that are there designed and built to accommodate those lanes too), 480 could have come and go on the outer lanes while 271 would have continued along on the inner lanes. (Instead, 2 lanes of each merge to form 3, and then the 3 split a couple miles later to 2+2--so staying on a route doesn't involve changing lanes but the roadways do combine. Close but not quite....)
I-80 and NJ 17 in Hasbrouck Heights, NJ where the interstate is inside NJ 17.
US 92 and I-4 near Tampa where US 92 is outside of I-4 at the interchange with US 301.
US 22 and Garden State Parkway in Union, NJ.
FL 15 and FL 408 in Orlando where FL 15 is the two service roads from Mills Avenue to Crystal Lake Drive.
FL 426 and I-4 in Downtown Orlando for one block from Robinson to Washington Streets.
CT 15 parallels I-91 in Meriden (south of I-691) and in Hartford (south of the Charter Oak Bridge). Meriden has I-91 inside the CT 15 lanes, and Hartford has each freeway side by side.
Something like that occurs with I-73 and I-85 on the Greensboro Urban Loop.
What about US 301 at I-95 North of Richmond, VA where US 301 is outside of I-95 through the interchange?
Quote from: Kacie Jane on January 22, 2012, 04:58:40 PM
Quote from: PennDOTFan on January 22, 2012, 04:40:09 PM
I-295 and the New Jersey Turnpike run parallel for quite a distance between the Delaware Memorial Bridge and up to Trenton.
That's not the sort of parallel routes he's talking about though. He's talking about specifically where one freeway is sort of "inside" another -- the way the Garden State Parkway and US 9 are between Exits 127 and 129, or I-295 and I-76 where the latter ends and turns into NJ 42.
Or, as NE2 cheekily pointed out, similar to any local/express setup, or the NJTP's truck and car lanes... except with two different freeways involved.
*D'oh* I see now.
How about I-85 and US 74 near Kings Mountain, NC?
http://g.co/maps/sgecx
Quote from: hbelkins on January 22, 2012, 08:17:58 PM
How about I-85 and US 74 near Kings Mountain, NC?
http://g.co/maps/sgecx
Looks like a winner.
I-205 & I-84/US 30 in Portland OR.
Quote from: roadman65 on January 22, 2012, 06:42:10 PM
What about US 301 at I-95 North of Richmond, VA where US 301 is outside of I-95 through the interchange?
Close, but 301 isn't a freeway there.
Quote from: national highway 1 on January 22, 2012, 09:56:14 PM
I-205 & I-84/US 30 in Portland OR.
I thought of this, too, but the freeways are side-by-side, not one inside the other like the example in the OP.
I-355 in Illy runs parallel with a free road whose number I cannot remember for the life of me
I-35W and I-94, Minneapolis
As for the longest one: AP-7 and B-30 in Barcelona, 6.5 miles long. http://cmap.m-plex.com/hb/hwymap.php?mt=g&r=esp.b030&sys=espa&rg=all&gr=p&off=100
The carriageways of Route 8 are in between the carriageways of Route 3 for about 2km, in Hong Kong.
http://g.co/maps/9hf2a (http://g.co/maps/9hf2a)
Technically "unbuilt" but had the I-80 realignment from Foothill Farms to midtown Sacramento been completed (instead of its cancellation leading to the old I-80/US 99E/US 40 becoming Business 80 in 1982), the new alignment would have run within the lanes of what is today's I-80 from exits 93 to 95, but what was originally I-880:
http://maps.google.com/maps?q=Foothill+Farms,+CA&hl=en&ll=38.643758,-121.391716&spn=0.037206,0.055189&sll=35.246145,-81.304021&sspn=0.019452,0.027595&vpsrc=6&hnear=Foothill+Farms,+Sacramento,+California&t=h&z=14
Quote from: agentsteel53 on January 23, 2012, 01:51:24 AM
I-355 in Illy runs parallel with a free road whose number I cannot remember for the life of me
I-355 and I-88, as well as I-290 and I-294.
SR 91 and 91 Express Lanes. The latter are technically a separate freeway.
Quote from: Grzrd on January 22, 2012, 04:09:08 PM
Years ago, to the southwest of Atlanta's Hartsfield (today known as Hartsfield-Jackson) Airport, I-85 and I-285 were duplexed for a short stretch between the interchange where I-85 was routed to the inside of I-285 and the interchange where I-85 was routed to the outside of I-285. Later, the two intersections were combined, for lack of a better phrase, into a large "mega-interchange" (http://maps.google.com/maps?q=atlanta+ga&hl=en&ll=33.620266,-84.47422&spn=0.0223,0.038409&sll=37.0625,-95.677068&sspn=43.25835,78.662109&vpsrc=6&hnear=Atlanta,+Fulton,+Georgia&t=h&z=15) in which the duplex was eliminated and I-85 and I-285 maintain independent routings.
Two questions:
(1) What is the longest parallel, non-duplexed routing of two interstates in the interstate system (same question for freeways, too)?
(2) I referred to it as a "mega-interchange"; should the system in the link above properly be considered as one interchange or two interchanges?
I-95 and FL Turnpike in Southern Martin County are literally right next to one another for a few miles.
I-696 and the Lodge NW of Detroit: 1.6 miles
I-88 and I-355: 1.3 miles
In the Bronx, the Cross Bronx Expressway straddles the Bruckner Expressway for about half a mile or so where I-95 transitions from one to the other and I-278 and I-295 begin and end. I think this is considered one huge interchange, though.
NJ 124 is the frontage roads of NJ 24 for over 2 miles, although 124 isn't a freeway.
Quote from: Upside down frog in a triangle on January 23, 2012, 08:12:10 PM
NJ 124 is the frontage roads of NJ 24 for over 2 miles, although 124 isn't a freeway.
Along those same lines, S.R. 84 forms the frontage roads for I-595 in South Florida, for about 10 or so miles (?). S.R. 84 is not a freeway in this case, either.
Dulles Toll Road (VA 267) and Dulles Access Road (unsigned VA 90004). The latter is entirely within the former for 10 miles.
Quote from: agentsteel53 on January 23, 2012, 01:51:24 AM
I-355 in Illy runs parallel with a free road whose number I cannot remember for the life of me
As Brandon noted - it's not a free road - it's I-88 Toll.
Going N-S, IL 53 runs parallel to I-355 for a good distance - but I don't think that counts here.
I-45 and I-10 downtown Houston
And in addition to IH 45 and IH 10, also Us 59 and TX 288 heading south of downtown form a parallel routing that is a good 16 lanes across. 59 forms the outer lanes and 288 is on the inside, with the northbound side of 288 basically forming the ramps to IH 45 from BOTH highways
The first half mile or so of I-71 is inside I-64 in Louisville.
A bit of the Central Florida Greenway straddles I-4 near Orlando.
There are outer roadways on I-270 and OH 161 in northeastern Columbus that could be considered a continuous (unnumbered) freeway, with never less than 2 lanes each direction.
The brand new "crosstown commons" interchange between i-35w & mn-62 south of Minneapolis employs this tactic.
How about FL 618 in Tampa, Florida with its reversable express lanes in the median of the main freeway? Its not only like I-395 in Virginia, but elevated and a totally seperate highway as its endpoints are different from FL 618's terminuses. The express Freeway goes from local streets in Brandon to Downtown Tampa with slip ramps between the main freeway and it. You MUST have SUNPASS to use it during its lane operations as it has NO TOLLBOOTHS on it at all. Nonetheless, they use the same alignement for miles.
Quote from: hbelkins on January 28, 2012, 02:41:17 PM
I have come to detest the terms "duplex" and "multiplex"
Quote from: NE2 on January 28, 2012, 03:36:22 PM
Quote from: xonhulu on January 28, 2012, 03:18:15 PM
"Overlap" is also better than "multiplex," but I dunno, somehow it doesn't seem like the most appropriate term to me. "Concurrency" still works best for me. However, if state DOT's prefer overlap, I'd rather use the term that's most official.
Depends on the DOT. Some do use concurrency. Personally I find that a bit stilted, but that's just me.
(above quotes from ""Exit" on Two 2di Duplex" thread)
I agree with NE2, xonhulu and HB that using an official term is preferable. I used the "d-word" in the title of this thread and the above-quoted thread because I have seen it used at roadgeek sites over the years; like HB, I've never really liked the term, either - just tried to speak the local language.
This thread has established that there are multiple instances of two independent routes converging to the point where one route has its carriageways inside of the carriageways of the other route, with each route maintaining independent signage and mileage markers. Is there a specific official (DOT, engineering, whatever) term for this type of alignment? Until one is uncovered, is the phrase "parallel routing overlap" adequate? Lends itself to a good acronym: "PRO" :hmm:
Quote from: vtk on January 28, 2012, 02:21:06 AM
There are outer roadways on I-270 and OH 161 in northeastern Columbus that could be considered a continuous (unnumbered) freeway, with never less than 2 lanes each direction.
No different than the "double freeway" ODOT built for I-270 between US 40/Main St and I-70 on the east side.
Quote from: Hot Rod Hootenanny on January 28, 2012, 09:47:48 PM
Quote from: vtk on January 28, 2012, 02:21:06 AM
There are outer roadways on I-270 and OH 161 in northeastern Columbus that could be considered a continuous (unnumbered) freeway, with never less than 2 lanes each direction.
No different than the "double freeway" ODOT built for I-270 between US 40/Main St and I-70 on the east side.
You missed the scope of my example.
One continuous unnumbered freeway from south of Easton Way to Little Turtle Way. It has I-270 in its median for a few miles, and OH 161 in its median for another mile or so. Arguably, it's not just the local lanes of either numbered highway.