Unusual Stacked Interchanges in Brisbane, Australia

[Peter Freeman]

It's only really the NW quadrant that has much space beyond what's required for the left turn. And the river is why that space is there. So I doubt there were plans for anything beyond the central flyover plus left turns.

Agreed, though that NW quadrant and even the SE quadrant could perhaps just accomodate a 270 degree loop - see the size of the loops at nearby N2J12 cloverleaf.

Indeed, if you look at the next junction along, which also seems to be futureproofed for a stackamond, one left turn takes up a vast amount of space: https://www.google.co.uk/maps/@-33.9607 ... a=!3m1!1e3

I hadn't noticed that one (N2J15).

There's yet another futureproofed stackamond in CT which seems to be in the Kliprivier Dr format with C/D lanes for the next junction:
https://www.google.co.uk/maps/@-33.8857 ... a=!3m1!1e3

Yes, interesting. In fact even the first one that I posted on, N2J14, has that potential, to the north and to the south, to conflate 3 adjacent junctions. Like Kliprivier Drive, though not exactly 'C/Ds'. Rather Texas-ish ... ?

Looking at all four examples now, I think there was, and is, no vision for free-flowing right turns.

I'm rather fascinated that these all exist in Suid Afrika. So, not as rare and unusual as I thought. SA, like me, must rate them highly, though only one of the four is currently a true stackamond.

Are there more?

[jackal]

It's only really the NW quadrant that has much space beyond what's required for the left turn. And the river is why that space is there. So I doubt there were plans for anything beyond the central flyover plus left turns.

Agreed, though that NW quadrant and even the SE quadrant could perhaps just accomodate a 270 degree loop - see the size of the loops at nearby N2J12 cloverleaf.

Indeed, if you look at the next junction along, which also seems to be futureproofed for a stackamond, one left turn takes up a vast amount of space: https://www.google.co.uk/maps/@-33.9607 ... a=!3m1!1e3

I hadn't noticed that one (N2J15).

There's yet another futureproofed stackamond in CT which seems to be in the Kliprivier Dr format with C/D lanes for the next junction:
https://www.google.co.uk/maps/@-33.8857 ... a=!3m1!1e3

Yes, interesting. In fact even the first one that I posted on, N2J14, has that potential, to the north and to the south, to conflate 3 adjacent junctions. Like Kliprivier Drive, though not exactly 'C/Ds'. Rather Texas-ish ... ?

Looking at all four examples now, I think there was, and is, no vision for free-flowing right turns.

I'm rather fascinated that these all exist in Suid Afrika. So, not as rare and unusual as I thought. SA, like me, must rate them highly, though only one of the four is currently a true stackamond.

Are there more?

A couple more in the Western Cape on the N1: https://www.google.co.uk/maps/@-33.8887 ... 354564,15z
https://www.google.co.uk/maps/@-33.8744 ... 648941,15z

And one in the Eastern Cape: https://www.google.co.uk/maps/@-33.9141 ... a=!3m1!1e3

So we're up to 7 in SA, mostly in the CT area.

It seems laying out a junction "for but not with" a stackamond was considered a good option where a future capacity increase may be needed. And as these are suburban sites, space may also have been a consideration, cloverleafs and 6RPs being fairly common alternatives in SA.

[Peter Freeman]

A couple more in the Western Cape on the N1:
https://www.google.co.uk/maps/@-33.8887 ... 354564,15z
https://www.google.co.uk/maps/@-33.8744 ... 648941,15z

These are of personal interest to me, as they are close (2.5km and 4km respectively) to my home in the late 1970's. The first is just a few hundred metres from where I dropped my daughter off at school each day. I don't remember them having this form in 1977. If they did, it didn't strike me as notable at the time.

The Bellville Park one is quite extended N-S, and it looks unsuitable for a flyover addition: there are many buildings between the R302 carriageways.

So we're up to 7 in SA, mostly in the CT area.

That's one actual stackamond, and six potentials (2-level G.S.squareabouts).

In AU, my count is three-
One stackamond (Gateway Motorway / Old Cleveland Road)
One potential (Sunshine Motorway / Maroochydore Road)
Another potential, but the squareabout is hybrid (Bruce Highway / Maroochydore Road).

[Peter Freeman]

Here's a short animation that shows the squareabout at Bruce Highway / Maroochydore Road north of Brisbane. Its strange shape arises from it being a recent conversion from a standard roundabout, and the wish to minimise new structures and disruption. It involved one straight bridge build, followed by one curved bridge demolition. It looks like a roundabout hybrid, but I think it would feel square, with the attendant advantage (in my view) of clear and easy navigation. Conversion to a stackamond is obviously not intended.
https://www.youtube.com/watch?v=YxNvjF0L5gc