AARoads Forum

National Boards => General Highway Talk => Topic started by: tradephoric on July 01, 2019, 11:45:19 AM

Title: Half-roundabout interchange?
Post by: tradephoric on July 01, 2019, 11:45:19 AM
Does any interchange like this exist?  I like it as it only has 2 conflict points in the entire interchange and traffic along the main arterial doesn't have to yield/stop.


Here is the original interchange i used as a template for this design...
https://www.google.com/maps/@27.416,-80.3884882,661m/data=!3m1!1e3
Title: Re: Half-roundabout interchange?
Post by: 1 on July 01, 2019, 11:47:34 AM
So you're requiring drivers to change lanes twice in 50 feet?
Title: Re: Half-roundabout interchange?
Post by: tradephoric on July 01, 2019, 02:15:21 PM
^I'm not 100% certain what you are referring to.  I guess you don't like it though.
Title: Re: Half-roundabout interchange?
Post by: kalvado on July 01, 2019, 03:05:46 PM
So you're requiring drivers to change lanes twice in 50 feet?
Just entering into further away lane. And yes, this is the concept of "modern roundabout".
Title: Re: Half-roundabout interchange?
Post by: kphoger on July 01, 2019, 04:39:33 PM
Yeah, I'm not seeing the double lane change either.
Title: Re: Half-roundabout interchange?
Post by: tradephoric on July 02, 2019, 07:48:12 AM
So you're requiring drivers to change lanes twice in 50 feet?

I cleaned up the model a little and this might fix the problem you were seeing.  So does any interchange like this exist?

Title: Re: Half-roundabout interchange?
Post by: MNHighwayMan on July 02, 2019, 08:55:58 AM
So does any interchange like this exist?

Nah. They're worried about half-tornadoes.
Title: Re: Half-roundabout interchange?
Post by: Road Hog on July 02, 2019, 09:18:35 AM
I would like to see a full freeway roundabout. The diameter would have to be a mile or more to maintain speed, so it could be only built in a rural setting.
Title: Re: Half-roundabout interchange?
Post by: kalvado on July 02, 2019, 10:56:11 AM
I would like to see a full freeway roundabout. The diameter would have to be a mile or more to maintain speed, so it could be only built in a rural setting.
I would expect sight distance to be a bigger concern. Vehicle entering roundabout have to be prepared to stop and yield to traffic already in the circle, which means observing traffic from pretty far away at highway speeds.
We do have roundabout here  on what is essentially a divided highway, though.
https://www.google.com/maps/@42.6452421,-73.8529353,378m/data=!3m1!1e3
 
Title: Re: Half-roundabout interchange?
Post by: tradephoric on July 02, 2019, 01:05:00 PM
I've been critical of multi-lane roundabouts but the movements in this roundabout are so simplified that i don't think the crash rate would be too high.  The only conflicts are off-ramp traffic and thru traffic along the arterial.  Also, all traffic entering the freeway doesn't have to transverse a roundabout or get stuck at a red light which is pretty nice.



Title: Re: Half-roundabout interchange?
Post by: jeffandnicole on July 02, 2019, 01:16:13 PM
It looks like it has some of the basic functions of the old 29/95 interchange North of Trenton, NJ.  NJ 29 swerved over and back to allow turns from the opposing direction onto and off of the highway.

It was a disaster because motorists weren't always sure which way to look, and is being replaced with true roundabouts.
Title: Re: Half-roundabout interchange?
Post by: tradephoric on July 02, 2019, 01:38:37 PM
^That NJ interchange (pre-roundabout version) is a total mess though.  I really don't think it's comparable to the model i posted.  Describing exactly what's happening in that NJ interchange requires a PHD in clusterf#$@ism!

(https://i.imgur.com/MqQCEAq.jpg)
https://www.google.com/maps/@40.2602883,-74.8450233,401m/data=!3m1!1e3

Title: Re: Half-roundabout interchange?
Post by: tradephoric on July 03, 2019, 12:44:38 PM
Here is another variation of this interchange.  The overlaid interchange pictured is US51 & I-74 south of Bloomington, Illinois.  I included a slip ramp at one of the off-ramp exits.

Title: Re: Half-roundabout interchange?
Post by: sprjus4 on July 03, 2019, 12:48:21 PM
Part of the issue with the whole idea is it seems fine on paper and watching traffic flow, but test it in reality. There's ought to be so much confusion with it.

https://www.google.com/maps/@36.8748352,-76.2122365,894m/data=!3m1!1e3!5m1!1e1

They put this CFI (continuous flow intersection) in here in Norfolk, VA, and there's been a lot of confusion with it, despite signage. Most people just aren't used to that type of intersection.

And to make matters worse, another intersection in Virginia Beach, VA under construction is creating a hybrid of a RCI (reduced conflict intersection), and CFI at a major intersections.

I can't wait to see the amount of confusion and wrecks that occur there when it's completed. These innovative designs may help traffic flow, but consider driver expectations as well. The VA Beach intersection goes too far IMO.
Title: Re: Half-roundabout interchange?
Post by: tradephoric on July 03, 2019, 01:31:47 PM
^Are you referring to the Indian River and Kempsville Road intersection they are planning?  That intersection may be a bit overkill.  Metro Detroit has a couple hundred Michigan left intersections but not one CFI.  The MUT functions just fine without the need to add an extra layer of CFI complexity.

(http://i478.photobucket.com/albums/rr144/tradephoric/Transportation%20Pictures/Random/1ab308237b311920_landing.jpg)
Title: Re: Half-roundabout interchange?
Post by: sprjus4 on July 03, 2019, 01:44:22 PM
^Are you referring to the Indian River and Kempsville Road intersection they are planning?  That intersection may be a bit overkill.  Metro Detroit has a couple hundred Michigan left intersections but not one CFI.  The MUT functions just fine without the need to add an extra layer of CFI complexity.
Yes.

But it's not being planned, construction started last year. I think it's planned to open next year.

https://www.vbgov.com/government/departments/public-works/roadways/Pages/indian-rvr-kemps-intersection.aspx

https://www.vbgov.com/government/departments/public-works/roadways/Documents/Kempsville%20IR%20Intersection/kemps-ir-intersect-display.pdf

My biggest concern is that none of the left turn are double lefts, only single lefts. There's currently double lefts, and it's a mistake to remove them.

The best alternative IMO was the grade-separated interchange. Yes, it costs more now, though in the long run, it would've been the best. The Indian River / Ferrell Pkwy corridor east of this is limited-access and part freeway, so it would've been a nice extension.
Title: Re: Half-roundabout interchange?
Post by: skluth on July 04, 2019, 01:59:55 PM
^^^^^^^^^^^^^^^^^^^^^^^^^

CFI's aren't that bad to use. They look strange, like DDI's.  This CFI in suburban St Louis (https://www.google.com/maps/@38.5041241,-90.4570266,426m/data=!3m1!1e3!5m1!1e1) works just fine. I've literally used it dozens of times as it was the best way to get to the AMC theater and Friar Tucks from MO 30 when I lived in Oakville. I never noticed any usage problems, although I've heard people complain because people like to complain. Most of the complaints were the "I don't like it/get off my lawn" variety with no specific complaint.
Title: Re: Half-roundabout interchange?
Post by: sprjus4 on July 04, 2019, 02:25:09 PM
^^^^^^^^^^^^^^^^^^^^^^^^^

CFI's aren't that bad to use. They look strange, like DDI's.  This CFI in suburban St Louis (https://www.google.com/maps/@38.5041241,-90.4570266,426m/data=!3m1!1e3!5m1!1e1) works just fine. I've literally used it dozens of times as it was the best way to get to the AMC theater and Friar Tucks from MO 30 when I lived in Oakville. I never noticed any usage problems, although I've heard people complain because people like to complain. Most of the complaints were the "I don't like it/get off my lawn" variety with no specific complaint.
They can be confusing for the average motorist, though it generally is fine. The one being constructed in Virginia Beach is a CFI and RCI combined, which looks very strange but supposedly works. Iíll have to try it out when it opens.
Title: Re: Half-roundabout interchange?
Post by: tradephoric on July 18, 2019, 08:00:08 AM
I made a model that modifies a planned Calgary interchange.  Not saying it would be better or worse.. just different.


(https://www.calgary.ca/Transportation/TI/PublishingImages/Road-projects/14-St-NW-Stoney-Trail-Interchange-design-2048px.jpg)