Diverging Diamond Interchanges

[Great Lakes Roads]

Cool map GLR, thanks for making!  How'd you do this?!  Seems tough with so many different sources!  Here's another pretty good one: https://go.ncsu.edu/intersects-interchanges

I'd suggest adding the 'REAL' first DDI: Thurbers Ave @ I-95 in Providence, RI.

And once you've mastered the DDI list, feel free to do 'others that are somewhat weird' (SPUI, displaced left, CFI, unique u-turns) 

Some news sources, DOT websites, knowledge, different threads for international ones... trust me, it was a LOT of work!

[1995hoo]

I see the next FL 23 First Coast Expressway expansion is building one for a new local road being added at Green Cove Springs north of SR 16 west of the city.

Neither road at the exchange were there prior to the construction and this one is one that will be built from scratch.

Gee, you don't say:

You've got a few of the under-construction DDIs on FL-23, the First Coast Expressway. It appears there's another one under construction with a road that apparently doesn't yet exist. You can see the telltale outline of a DDI on the bottom part of this satellite image. I don't know how you'd describe this on the map index, though.

[Chris]

Belgium is constructing its second DDI at the N4 / N25 intersection near Louvain-la-Neuve.



This is its location, it was a roundabout until now: https://www.google.com/maps?ll=50.65878,4.63532&z=16&t=h

[pderocco]

Belgium is constructing its second DDI at the N4 / N25 intersection near Louvain-la-Neuve.



This is its location, it was a roundabout until now: https://www.google.com/maps?ll=50.65878,4.63532&z=16&t=h

Why is it so fat? That looks way more expensive than it needs to be.

But hey, it's only their second try.

[mgk920]

Belgium is constructing its second DDI at the N4 / N25 intersection near Louvain-la-Neuve.



This is its location, it was a roundabout until now: https://www.google.com/maps?ll=50.65878,4.63532&z=16&t=h

Why is it so fat? That looks way more expensive than it needs to be.

But hey, it's only their second try.

It was a BIG roundabout before the Belgian highway people started to convert it to a DDI, reusing as much of the former interchange as possible to save €€€€.

Mike

[freebrickproductions]

Belgium is constructing its second DDI at the N4 / N25 intersection near Louvain-la-Neuve.



This is its location, it was a roundabout until now: https://www.google.com/maps?ll=50.65878,4.63532&z=16&t=h

Why is it so fat? That looks way more expensive than it needs to be.

But hey, it's only their second try.

It was a BIG roundabout before the Belgian highway people started to convert it to a DDI, reusing as much of the former interchange as possible to save €€€€.

Mike

It looks like the roundabout was at-grade though?

[jakeroot]

The layout on the north-northeast corner of the interchange was confusing me. Luckily I found a YouTube video showing the final layout. The northeast leg includes some kind of loading area ("places"?) that the off-ramp wraps around. That's why there's also this ramp seemingly going the wrong direction, as well as a U-turn slip lane in the nearby corner (relative to the above photo):

[kphoger]

The northeast leg includes some kind of loading area ("places"?) that the off-ramp wraps around.

I bet that's a large rideshare lot.  Compare the road sign icon they used in the video with the standard road sign for that.

[Chris]

Yes, it's a carpool parking.

Initially, governments truly believed that carpooling would reduce traffic on major highways, though they have a capacity that's the equivalent of like 1 minute of freeway traffic passing by.

Nowadays it's built to cater to a need, these carpool lots tend to be fairly well used. Not as much for carpooling into a city, but more often by workers who commute to a job site.

Wallonia built a carpool lane on the shoulder of E25 to the Luxemburg border that's seen virtually no usage, it's considered a huge flop.

Here are some more photos of that DDI:

[wanderer2575]

Unusual (at least I think so) traffic control at the new I-69/BL I-94/M-96 DDI in Marshall, MI.  Ramp traffic turning west has a signal and No Turn on Red, while ramp traffic turning east has only a stop sign.  Might that be because each ramp has only one lane turning east?

Southbound exit ramp:


Northbound exit ramp:

[jakeroot]

Unusual (at least I think so) traffic control at the new I-69/BL I-94/M-96 DDI in Marshall, MI.  Ramp traffic turning west has a signal and No Turn on Red, while ramp traffic turning east has only a stop sign.  Might that be because each ramp has only one lane turning east?

Southbound exit ramp:


Northbound exit ramp:

Unsignalized double or triple turns are pretty rare. There's some examples around Phoenix (like here), and South Africa (here)...but overall they're not common. I've actually never seen a triple turn that wasn't signalized somehow.

But single-lane movements are very often stop or yield control. Some states, like here in WA, apparently have a policy to signalize all DDI movements with no-turn-on-red signs. Other states don't have that rule, though.

In terms of your example, I am not surprised to see the signalized two lane and three lane turns, but the stop-controlled turns are certainly less common. They could have been yields, though, especially being curb to curb turns.

[kphoger]

Unsignalized double or triple turns are pretty rare.

Not sure if this is the sort you're looking for, but Wichita used to have an example here, before they redid it:

https://maps.app.goo.gl/nxdcBT81K28fEvBd6

Honestly, it worked better the old way.

[ET21]

Another DDI for northern Illinois, this one at I-39 and Harrison Ave in Rockford (part of the I-39 upgrade). Opened up a few months ago
https://www.google.com/maps/@42.2398656,-88.9647468,17.49z/data=!5m1!1e1?entry=ttu&g_ep=EgoyMDI2MDQxNC4wIKXMDSoASAFQAw%3D%3D

[kphoger]

Another DDI for northern Illinois, this one at I-39 and Harrison Ave in Rockford (part of the I-39 upgrade). Opened up a few months ago
https://www.google.com/maps/@42.2398656,-88.9647468,17.49z/data=!5m1!1e1?entry=ttu&g_ep=EgoyMDI2MDQxNC4wIKXMDSoASAFQAw%3D%3D

Let's just slap those yellow [TOLL] banners wherever the heck they'll fit!  https://maps.app.goo.gl/gfcQ3MB1WCt8ADuU6