New intersection experience

[wdfifteen]

I had to deliver a bicycle to Carmel, Indiana (northeast of Indianapolis). Getting there on the under-reconstruction I-70 was so brutal I took back roads home. It’s been at least a decade since I was up there, man have things changed. Every other intersection is a roundabout – it’s downright dizzying. And then BAMB! you’re right in the middle Amish country sharing the road with horse-drawn carriages. I came up on a traffic light and before I knew it I was in the middle of a strange, interesting intersection and I was not real confident I was going through it properly. I just went with the flow and quickly found myself on the I-69 North, like socks on a rooster. It was actually pretty smooth and quick.

I’ve read about them – “Compound Inverse Double Divergent Inverted Diamond Interchange” or something like that. When I got home, I Googled it - and what do you know, the first picture that popped up was the very intersection I experienced! I guess they are still relatively rare.

Are there any around you?



I was coming from the West (right of the picture) and turning on North onto I69 (bottom of the picture).

Now if they just replace the traffic lights with roundabouts we would never have to stop for anything.

[stevej37]

We've had a couple of them for about 7 years now. They are a lot safer because they eliminate oncoming traffic trying to make a left turn in front of you.
I heard the cost is very high to change one over.

[greglepore]

We have a few. Disorienting, but they work.

[herr_oberst]

It makes sense when you stare at it long enough. I wouldn't want that in Portland or Seattle traffic with all the idjitts trying to figure it out on the fly.

Socks on a rooster. 🤔

[trials935]

Union Center exit off I75 just north of Cincinnati is like that for at least 10 years if not longer. Works well.

[p911dad]

The traffic engineers in NCDOT are in love with them and they are popping up all over. If you hit one at night and aren't aware of how they work it could get dicey for the unaware driver.

[vash]

kinda cool.

as an engineer, we quickly discovered how challenging it is to maintain a roundabout. you cant do a lane closure in the smaller ones!! opps. we pave ours with thick concrete now to defer the need for a shut down until way after we have all retired.

[Zeke]

I don't see the advantage. Still signals. I think I've seen Also tell me how you go north on I-69 to left on Dupont.

Maybe it's too early and I need coffee.

Cloverleafs don't need signals. The do take up more real estate. Is that the point of these things? Anyway we don't need those here. Any signal can mean 2, 3 or 4 cycles to get through at rush hour.

[stevej37]

"A Diverging Diamond Interchange (DDI) is a road design that shifts traffic to the opposite side of the road, allowing vehicles to make free-flowing left turns onto highways, reducing congestion, and improving safety by cutting conflict points by nearly 50%. It operates with two-phase signals, speeding up traffic, often at a lower cost than traditional, larger interchanges."

[vash]

I think they eliminate the left turn driver to driver contact? we dont have them here..

[Gogar]

Without these kinds of projects there would be even more recent college graduates out of work and even less construction companies doing uncontested bid work and even less city, county, and state administrators hiding cash in shoe boxes.

The traffic would be the same IMO

[masraum]

Originally Posted by Zeke

I don't see the advantage. Still signals. I think I've seen Also tell me how you go north on I-69 to left on Dupont.

Maybe it's too early and I need coffee.

Cloverleafs don't need signals. The do take up more real estate. Is that the point of these things? Anyway we don't need those here. Any signal can mean 2, 3 or 4 cycles to get through at rush hour.

If I understand your question correctly, I think the red line would be the route to go from Northbound on 69 to Westbound on Dupont.




I don't trust folks in Houston to get one of these right. I feel like we have too many people that either don't have a license or just shouldn't have a license.

[masraum]

Interesting. I think these have been posted about here a few times before.

It looks like there are 7 in Texas, but none anywhere that I'm likely to end up any time soon.

https://divergingdiamond.com/loc/texas/

[stevej37]

https://forums.pelicanparts.com/off-topic-discussions/1132231-diverging-diamond-interchanges.html

Post #8 has a video on how to drive thru one.

[3rd_gear_Ted]

That street & lane layout is very common in Mexico when a bridge is involved.
Slowly the states are getting smarter.

[A930Rocket]

I think I’ve seen the DDI at Ashford Dunwoody Road and 285 in Atlanta

What happens when you are the inside blue line driver, and the outside red line driver is exiting the roundabout after you? It seems like there’s going to be an accident.

[rwest]

Originally Posted by A930Rocket

I think I’ve seen the DDI at Ashford Dunwoody Road and 285 in Atlanta

What happens when you are the inside blue line driver, and the outside red line driver is exiting the roundabout after you? It seems like there’s going to be an accident.

The red line lane user is only supposed to turn right or go straight and there would be signs posted saying that, of course that doesn’t mean they wouldn’t try!

If they do the wrong thing, the speeds are slow enough to spare lives and just mess up body work.

[masraum]

Originally Posted by A930Rocket

I think I’ve seen the DDI at Ashford Dunwoody Road and 285 in Atlanta

What happens when you are the inside blue line driver, and the outside red line driver is exiting the roundabout after you? It seems like there’s going to be an accident.

I had to go back and look at your post twice since the first sentence was about DDI and then the second bit was a roundabout.

I think in the case that you've drawn, both of the lines in the roundabout are folks that did it wrong. The red line should have been the "inside" lane and the blue person should have been in the outside lane.

[MBAtarga]

In Metro Atlanta - there are half a dozen or more rather busy intersections that have been converted in the last decade or so to the Diamond interchange. They can be confusing for someone not familiar with the revised traffic flow.

All over the Atlanta suburbs the roundabouts are showing up on road enhancements for better traffic flow. It's frustrating how some drivers don't understand the difference between the Yield sign on a roundabout and a Stop sign at a 4 way intersection. If there is not another car in sight anywhere - why in the world do they come to almost a complete stop when they reach the Yield sign?

[DonDavis]

Agree with Steve, red and blue should swap. We have plenty here and they work well.

It’s rare I notice a newbie, but when it happens it just means things really slow down. And it’s over quickly.
I like ‘em.

Here’s a DDI in Johnson City, Tennessee.