Half-Parclo A4, Half Roundabout Interchange

[jakeroot]

So I whipped up this in Illustrator today, after a design I accidentally drew while waiting for my Physics professor to come to class.



Does anyone know if something like this A) exists, or B) is even feasible? I love Parclo A4/B4s and dumbell interchanges so I combined them into one.

One issue I see is that traffic might back up into the roundabout from the signal of the slip lane coming off the freeway. Any others?

Also, if this is the wrong section for this type post, please redirect me to its proper place. As you can tell by my total posts, I'm fairly new to AARoads.

[tradephoric]

Not really sure if any of these are exactly what you are looking for, but these should be of some interest:

https://maps.google.com/?ll=41.696412,-70.384512&spn=0.004518,0.006899&t=h&z=17
https://maps.google.com/?ll=35.11020,-85.22898&z=17&t=h
https://maps.google.com/?ll=42.95102,-88.108721&spn=0.008858,0.013797&t=h&z=16
https://maps.google.com/?ll=46.563036,-120.472126&spn=0.00416,0.006899&t=h&z=17
https://maps.google.com/?ll=39.223926,-76.807373&spn=0.004688,0.006899&t=h&z=17
https://maps.google.com/?ll=42.50545,-83.75794&z=17&t=h
https://maps.google.com/?ll=39.144973,-76.901003&spn=0.004693,0.006899&t=h&z=17
https://maps.google.com/?ll=39.32366,-77.35724&z=17&t=h

This one is a bit peculiar that i found interesting:
https://maps.google.com/?ll=41.94658,-74.027102&spn=0.009001,0.013797&t=h&z=16

[cpzilliacus]

Not the same, but here is as close as I could get (and admittedly not that close) in terms of something that's been built, Md. 5 (Leonardtown Road) at Md. 235 (Prince Frederick Road) in Hughesville, Charles County.

[cpzilliacus]

There's also this in a suburb of Helsinki, Finland at the junction of Highways 170 and  103.  Highway 170 would probably be classified as an expressway in the U.S.  Most of Highway 103 would be considered a freeway, it's also Ring III, the outermost of three circumferential highways in the region.

And this this along Highway 101, Ring I, functional class expressway.

[english si]

tradephoric's I-43 one is almost functionally identical - the only 5 ramp one posted, just that there are two roundabouts, rather than half a dog bone and some lights.

https://maps.google.com/?ll=42.95102,-88.108721&spn=0.008858,0.013797&t=h&z=16

Most of the others are merely (sometimes quasi-) 4-ramp parclos with roundabouts, rather than lights. Some weren't even that (eg trumpet ending on roundabout).

[Brandon]

tradephoric's I-43 one is almost functionally identical - the only 5 ramp one posted, just that there are two roundabouts, rather than half a dog bone and some lights.

https://maps.google.com/?ll=42.95102,-88.108721&spn=0.008858,0.013797&t=h&z=16

Most of the others are merely (sometimes quasi-) 4-ramp parclos with roundabouts, rather than lights. Some weren't even that (eg trumpet ending on roundabout).

The loop ramp on that I-43 one could be removed with no ill effects on the interchange or being able to get on the freeway.  Instead, the roundabout would work more like a Michigan Left for that movement.

[tradephoric]

A bit off topic, but that northern most roundabout in the I-43 example is one of the few 3-laned roundabout in the USA.  I only know of about a dozen roundabouts that are at least partially 3-lanes. 

[tradephoric]

Getting farther off topic, how bout a roundabout in the middle of a freeway median?

https://maps.google.com/?ll=39.100263,-76.768824&spn=0.003372,0.004823&t=h&z=18

[tradephoric]

Trying to get back on topic... this is actually pretty close to the OP picture but the roundabout only services on-ramp traffic (and is offset to the south of the main road).

https://maps.google.com/?ll=38.348034,-90.395336&spn=0.006815,0.009645&t=h&z=17

[tradephoric]

Here's a great  parclo/roundabout example from Washington State:

https://maps.google.com/?ll=46.238218,-119.242752&spn=0.008371,0.013797&t=h&z=16

[cpzilliacus]

Found this on the Sabre-Roads (UK) Web site from Italy (the discussion thread there was about temporary signage), but the roundabouts involved could be relevant to this thread.

[jakeroot]

Well I am absolutely ecstatic by the amount of responses I got to my inquiry. So far as aesthetics are concerned, this is my favorite type of interchange, so I was really excited to see this:

Here's a great  parclo/roundabout example from Washington State:

https://maps.google.com/?ll=46.238218,-119.242752&spn=0.008371,0.013797&t=h&z=16

Functionally, this junction is identical to what my initial post described. More exciting, I only live about a 5 hours drive away from this junction (western to eastern Washington). Someday I'm going to have to check it out. I was in the Tri-Cities (Richland, Pasco, Kennewick) just a few months ago; if only I knew about this junction, I would have checked it out. Also for the ramp coming from SR 240 West towards Columbia Park Trail, why is it that WSDOT feels the need to not install a slip lane? They rarely install them anymore.

Found this on the Sabre-Roads (UK) Web site from Italy (the discussion thread there was about temporary signage), but the roundabouts involved could be relevant to this thread.

Was it the original junction or the new junction that might be relevant? Both are pretty cool but not really to my liking. I can't say I love BIG rotary's. Unless they are signed really well.

[cpzilliacus]

Found this on the Sabre-Roads (UK) Web site from Italy (the discussion thread there was about temporary signage), but the roundabouts involved could be relevant to this thread.

Was it the original junction or the new junction that might be relevant? Both are pretty cool but not really to my liking. I can't say I love BIG rotary's. Unless they are signed really well.

I don't know.  I have never been at that location, but after I saw it discussed on Sabre-Roads (though the subject there was temporary signs), I thought it could be relevant to this thread.