I was playing around with Google Maps a bit, and I noticed that just outside Castaic, California, I-5 crosses over itself for a few miles. Looking around some more, I found that I-8 also crosses over itself just outside Yuma, Arizona.
I-5 crossing itself (Image from Google Maps)
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi61.tinypic.com%2F29fynvp.png&hash=9dcb04b4f8d34ca955fe7e56473168828f71319d)
I-8 crossing itself (Image from Google Maps)
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi61.tinypic.com%2F290tx8z.png&hash=123b5731829346af01e664fe45b4a12488b0d5b7)
I had a few questions about this phenomenon.
First, are there any other crossovers like this? I would imagine most would be in mountainous areas, but I couldn't be sure.
Second, why did the engineers who designed these highways decide to have them cross like this? What purpose does it serve?
And finally, is there anything in the MUTCD about crossovers? I noticed that there are no exits from either I-5 or I-8 when they are crossed, but I don't know if that's just a coincidence.
The only one I think I have driven is on I-85 in North Carolina, between US 64 and Thomasville.
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2FLOZX7pLl.png&hash=c7ef822434b2b4c74c40907adce62307b5949e79) (http://imgur.com/LOZX7pL)
I 95 used to cross over itself at the eastern junction of the Baltimore beltway, but it no longer does so after the huge reconstruction project.
Autoroute 20 approaching Montreal from the southwest. I'm posting via iPad and don't know of a way to get a map link on here, so I'll edit this later unless someone else posts a link in the meantime.
Edited to add: Map link here– https://www.google.com/maps/@45.4584879,-73.6116237,15z . The satellite view is kind of grainy and you have to zoom in fairly close to see the crossover, so I've linked the map instead.
The I-85 segment shown above has a rest area, with a Vietnam Veterans memorial, in the median partway through the segment. I've heard it theorized that the crossover exists in part to allow for right-side exits from both directions. I have no idea whether that is accurate.
North Carolina also has I-77/US 21 in Charlotte through the interchange with I-85. Presumably this was to make the footprint of the interchange smaller.
https://goo.gl/maps/b3SPN
Also, I-70 does this within tunnels at MM 125 in Glenwood Canyon
https://goo.gl/maps/6Snq7
Mapmikey
There's the 495 Helix at the Lincoln Tunnel.
Quote from: jp the roadgeek on July 10, 2014, 08:00:54 AM
I 95 used to cross over itself at the eastern junction of the Baltimore beltway, but it no longer does so after the huge reconstruction project.
AFAIK, I 695 still crosses over itself in that interchange. The construction of the HOT lanes is supposed to straighten that out, but that has not happened yet.
The I-65 and I-20/59 interchange in Birmingham shows each lane of travel crosses over (and back) at the other side of the "knot".
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fmaps.google.com%2Fmaps%2Fapi%2Fstaticmap%3Fcenter%3D33.5215%2C-86.826%26amp%3Bsize%3D640x640%26amp%3Bzoom%3D16%26amp%3Bmaptype%3Dhybrid%26amp%3Bsensor%3Dfalse&hash=e28f0b470e1777f0e6738f6c229ab7590e3e7081)
Does it count if one is the old route that carries truck traffic?
US 1/9 in NJ crosses over old US 1/9 (Truck 1/9 now) on the pulaski skyway.
Quote from: jeffandnicole on July 10, 2014, 08:14:07 AM
There's the 495 Helix at the Lincoln Tunnel.
if this counts, then so does the I-95 cloverleaf in Canton, MA.
It occurs to me that an honorable mention might go to the Lotus Bridge connecting China and Macau. Mainland China drives on the right while Macau drives on the left. The bridge is designed to shift traffic to the proper side of the road by having the carriageways crossing each other in a looping configuration on the Chinese side. I'm not sure it's fair to call this a "highway" in the sense the original post uses it, however, which is why I suggested an "honorable mention":
https://www.google.com/maps/@22.1392267,113.5483006,994m/data=!3m1!1e3
Edited to add: Here's a more "standard" carriageway cross-over on I-275 in St. Petersburg, Florida. I've driven this stretch southbound several times but never realized the carriageways cross over each other. I don't know why it's designed this way:
https://www.google.com/maps/@27.7196888,-82.6756372,17z
Newfound Gap Road in the Great Smoky Mountains National Park.
US 16A south of Mount Rushmore
Quote from: hbelkins on July 10, 2014, 12:55:56 PM
Newfound Gap Road in the Great Smoky Mountains National Park.
US 441. I-85 in North Carolina crosses itself so they only had to build one rest area.
iPhone
Quote from: formulanone on July 10, 2014, 09:32:13 AM
The I-65 and I-20/59 interchange in Birmingham shows each lane of travel crosses over (and back) at the other side of the "knot".
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fmaps.google.com%2Fmaps%2Fapi%2Fstaticmap%3Fcenter%3D33.5215%2C-86.826%26amp%3Bsize%3D640x640%26amp%3Bzoom%3D16%26amp%3Bmaptype%3Dhybrid%26amp%3Bsensor%3Dfalse&hash=e28f0b470e1777f0e6738f6c229ab7590e3e7081)
The I-196/US 131 interchange in Grand Rapids is exactly like this, except only US 131 crosses over itself.
Quote from: dfilpus on July 10, 2014, 01:07:18 PM
US 16A south of Mount Rushmore
similarly, old US-99 in Oregon, very near the CA state line.
Quote from: agentsteel53 on July 10, 2014, 10:38:28 AM
Quote from: jeffandnicole on July 10, 2014, 08:14:07 AM
There's the 495 Helix at the Lincoln Tunnel.
if this counts, then so does the I-95 cloverleaf in Canton, MA.
If that counts then so does every single interstate that switches highways at cloverleafs and several that enter a turnpike at an interchange.
Quote from: CtrlAltDel on July 10, 2014, 04:37:05 AM
Second, why did the engineers who designed these highways decide to have them cross like this? What purpose does it serve?
Hazarding a guess here: the grade/right-of-way for a former railroad or a previously-built highway was only wide enough to support one Interstate-grade carriageway, and could not be made wider, so the easiest way to construct the opposite direction's carriageway was to "thread" it around the existing one using a new right-of-way. (Do I win?)
Quote from: hubcity on July 10, 2014, 02:17:21 PM
Hazarding a guess here: the grade/right-of-way for a former railroad or a previously-built highway was only wide enough to support one Interstate-grade carriageway, and could not be made wider, so the easiest way to construct the opposite direction's carriageway was to "thread" it around the existing one using a new right-of-way. (Do I win?)
I-5 is indeed the case. the northbound lanes were the original Five Mile Grade, and the southbound lanes were added where they could be.
I am not sure about I-8, since historially US-80 followed the railroad west of Wellton, multiplexing with US-95 to enter Yuma. there may have been a two-lane alignment across Telegraph Pass, though.
Quote from: hubcity on July 10, 2014, 02:17:21 PM
Hazarding a guess here: the grade/right-of-way for a former railroad or a previously-built highway was only wide enough to support one Interstate-grade carriageway, and could not be made wider, so the easiest way to construct the opposite direction's carriageway was to "thread" it around the existing one using a new right-of-way. (Do I win?)
The right of way issue you describe can be a reason. As for the crossover issue, especially in mountainous terrain, the likely reason is that the second roadway had to be constructed in less favorable terrain grade-wise. The second road was likely steeper or curvier, and engineers probably thought to swap them so as to not have trucks going down a steeper/curvier downhill grade. By casual observation of the pic above, this might be the case with the I-8 example.
Seeing Cody's pictures of his trip to NYC reminds me of another example: US 33 in Ravenswood, WV.
I-275 crosses over itself at the north end of the Sunshine Skyway Bridge in St. Petersburg, FL. Also the FL 112 freeway entering MIA crosses itself adjacent to LeJune Road.
I-76 in Youngstown, OH at I-80. Both directions cross over themselves at least once. Eastbound crosses over itself twice more in the double trumpet.
I-70 in Breezewood, PA (good time to mention that I hate that interchange (if you can call it that)).
If we're counting trumpets, then I-90 east of Albany, NY at Exit B1 and I-76 next to the King of Prussia Mall.
Quote from: getemngo on July 10, 2014, 01:13:59 PM
Quote from: formulanone on July 10, 2014, 09:32:13 AM
The I-65 and I-20/59 interchange in Birmingham shows each lane of travel crosses over (and back) at the other side of the "knot".
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fmaps.google.com%2Fmaps%2Fapi%2Fstaticmap%3Fcenter%3D33.5215%2C-86.826%26amp%3Bsize%3D640x640%26amp%3Bzoom%3D16%26amp%3Bmaptype%3Dhybrid%26amp%3Bsensor%3Dfalse&hash=e28f0b470e1777f0e6738f6c229ab7590e3e7081)
The I-196/US 131 interchange in Grand Rapids is exactly like this, except only US 131 crosses over itself.
The I-77/I-85 interchange in Charlotte, NC also does this.
Quote from: Mapmikey on July 10, 2014, 08:07:22 AM
Also, I-70 does this within tunnels at MM 125 in Glenwood Canyon
https://goo.gl/maps/6Snq7
Mapmikey
As a local who travels thru Glenwood Canyon frequently, the Hanging Lake Tunnels run side by side and
do not cross over each other.
Quote from: 1995hoo on July 10, 2014, 11:22:53 AM
It occurs to me that an honorable mention might go to the Lotus Bridge connecting China and Macau. Mainland China drives on the right while Macau drives on the left. The bridge is designed to shift traffic to the proper side of the road by having the carriageways crossing each other in a looping configuration on the Chinese side. I'm not sure it's fair to call this a "highway" in the sense the original post uses it, however, which is why I suggested an "honorable mention":
https://www.google.com/maps/@22.1392267,113.5483006,994m/data=!3m1!1e3
Also in China, you have G5 expressway crossing over itself
twice in central Sichuan. G30 also does this in Northwestern Xinjiang.
About carriageway crossovers, I can think of a section Spanish A-23 currently U/C which will do so when completed on February 30th.
In Italy, the A6/E717 does it several times west of Savona. The eastbound carriageway also goes under itself in a tunnel.
What about PA 3 in Philadelphia, PA? Though not a freeway, but EB PA 3 crosses over WB PA 3 at grade so it has a one way pair but in reverse order.
MD 139 SB crosses over its NB lanes at grade to be aligned on St. Paul Street which is east of Charles Street that carries one way NB MD 139 in Baltimore.
I agree - do not trust the routing Google Maps (or any map engine) has laid out - they don't know
AZ SR 87 (Beeline Hwy) does a crossover of itself similar to I-5 and I-8.
As a matter of opinion, trumpet interchanges (especially the standard ones) should not be included in this category because they do this by design. The same should be the same for Diverging diamond interchanges, Cloverleafs, etc.
Similarly, IL 97/29 in Springfield crosses over itself to connect to a one-way pair: https://goo.gl/maps/Hl8va. The eastern end of the pair is at-grade, and the western is an overpass.
EDIT: Huh, they rerouted 29 around town since the last time I was there.
Then should we consider US 1 in DC that way? It NB alignment crosses its SB alignment just north of the 14th Street Bridge to continue on 14th St. SW while the SB US 1 is concurrent with I-395 SB as it uses the 9th Street Tunnel instead of 14th Street and avoids using Constitution Avenue like its NB counterpart does. Then also, at grade, NB crosses SB again at Constitution Avenue at 9th Street NW.
Until the late 1970s, I-84 had a short crossover near the Brass Mill in Waterbury (exit 22).
1965 aerial photo is here: http://cslib.cdmhost.com/cdm/singleitem/collection/p4005coll10/id/12303
Only source I have on the fix right now is the contract award in 1976 -- "State Awards Contract for I-84 Project", Hartford Courant, Sept. 3, 1976
EDIT: in Connecticut :-)
Not a highway, but East Sky Harbor Blvd at PHX crosses over itself for most of its length through the airport:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Fhx9t22j.png&hash=9b68e9be65aff7b1b72023a4fff820a81034913d)
Quote from: Mapmikey on July 10, 2014, 08:07:22 AM
Also, I-70 does this within tunnels at MM 125 in Glenwood Canyon
https://goo.gl/maps/6Snq7
No it doesn't. That's just poor map data approximating the eastbound tunnel as two straight lines instead of the curve it actually takes. The two tunnels don't cross.
For another former example, I-84 as originally built had a crossover at exit 22 in Waterbury, CT.
Here is a 1965 aerial photo:
(https://www.aaroads.com/forum/proxy.php?request=http%3A%2F%2Fi.imgur.com%2Fo6zSq3G.png&hash=64ae4a50a891816c09bfc7251a39752dc73cf5a4)
Same spot today: https://www.google.com/maps/@41.550052,-73.0309227,1094m/data=!3m1!1e3
Yes, those two photos are the same spot. Surroundings have changed a lot in 50 years as well, eh?
This was modified to a more normal configuration the highway was widened from 4 to 6 lanes. In doing so the left exit and entrance for eastbound traffic were eliminated.
Quote from: Duke87 on July 13, 2014, 06:57:19 PM
For another former example, I-84 as originally built had a crossover at exit 22 in Waterbury, CT.
Here is a 1965 aerial photo:
Same spot today: https://www.google.com/maps/@41.550052,-73.0309227,1094m/data=!3m1!1e3
Yes, those two photos are the same spot. Surroundings have changed a lot in 50 years as well, eh?
This was modified to a more normal configuration the highway was widened from 4 to 6 lanes. In doing so the left exit and entrance for eastbound traffic were eliminated.
Kurumi already mentioned this one. :D I don't know about you, but sometimes with these listing threads, it becomes a too long; didn't read type of thing and things up getting double posted a lot in my experience.
NY 363 in Binghamton, NY. The entrance ramp to eastbound NY 363 from NY 434 is north of westbound NY 363. They cross over about 1/4 mile east of NY 434.