Parclo A4/B4 Interchanges outside of North America

[jakeroot]

I was looking at Helsinki's ring roads when I discovered something rather peculiar: a Parclo A4 interchange! Granted, it isn't very pretty, but it got me wondering if the Parclo A4/B4 interchange design is used outside of North America. I've spent much of my free time surveying other countries' roads, and other than this rather ugly variation near London, England, and a number near Johannesburg, they seem to be relatively absent.

Anyone know of locations using this design outside of North America?

Some interchanges seem to be used much more often in some locals. North America has the Parclo A4/B4 or diamond, the UK has the roundabout, Germany has the cloverleaf, and Japan has the trumpet with a tollbooth on one end, and so on. Not sure that has relevance to this topic, but it's something to think about.

[sammi]

In the Philippines, I know of a few. (Note, the exit numbers are not labeled on Google Maps.)

Tabang Spur Road exit 27 in Guiguinto, Bulacan. Aerial view
North Luzon Expy exit 38 in the same town. Aerial view
South Luzon Expy exit 9 in Pasay City, Metro Manila. Aerial view. It's under the directional T.

A few other parclos exist, but they're neither A4 nor B4 so they're not going here.

Because every expressway in the Philippines is tolled, the trumpet interchange is preferred for the newer ones, for cheaper construction of toll facilities and such. The 60s-era NLEX and SLEX used more different types of interchanges, whereas the newer SCTEX and TPLEX use pretty much only trumpets.

[jakeroot]

Because every expressway in the Philippines is tolled, the trumpet interchange is preferred for the newer ones

If I was the Phillipines, I would have always used the trumpet interchange to begin with! Then again, electronic EZ-Pass systems work waaaaaaaayyy better.

[jakeroot]

Wow, ancient thread.

Found a new example from Australia. North of Brisbane, along the Bruce Hwy @ Boundary Road.



Note the very nicely designed loops and off-ramps (nothing too unusual ... very normal looking A4) and the very nice pedestrian overpass.

[CtrlAltDel]

Wow, ancient thread.

True, but, in combination with your Australian picture, it gives me the perfect occasion to say that I think the A and B labels in parclo interchanges should be reversed, with A representing loop ramps "after" and B "before" the arterial road.

[jakeroot]

Wow, ancient thread.

True, but, in combination with your Australian picture, it gives me the perfect occasion to say that I think the A and B labels in parclo interchanges should be reversed, with A representing loop ramps "after" and B "before" the arterial road.

And I'm here to say that I absolutely agree with your assessment. I've never quite understood why A was "A" and B was "B", given the "after" and "before" explanation.

[kphoger]

At the risk of stating the obvious, 'A' comes before 'B' in the alphabet.

[CtrlAltDel]

At the risk of stating the obvious, 'A' comes before 'B' in the alphabet.

True. At the risk of stating the obvious, though, no one disputes that.

Or less snarkily, why is the order of the alphabet relevant to the current discussion? It's not like there's an interchang-ical order that it should match.

[kphoger]

If the 'BEFORE' one should be 'B' and the 'AFTER' one 'A', though...  Maybe, instead, the first one (the one encountered 'before') should be the first letter of the alphabet and the next one (the one encountered 'after') should be the next letter of the alphabet.

[CtrlAltDel]

If the 'BEFORE' one should be 'B' and the 'AFTER' one 'A', though...  Maybe, instead, the first one (the one encountered 'before') should be the first letter of the alphabet and the next one (the one encountered 'after') should be the next letter of the alphabet.

So, in essence, you're saying that there is in fact an "interchang-ical" order?

[kphoger]

Weren't you saying that by bringing up 'before' and 'after'?  That sounds like an interchang-ical order to me.

[CtrlAltDel]

Weren't you saying that by bringing up 'before' and 'after'?  That sounds like an interchang-ical order to me.

Well, no. The positioning of elements within an interchange is different from the ordering of different interchanges among one another. The first is a distinctive element of the interchange's design, which cannot be changed without making it into a different kind of interchange, while the other is more or less arbitrary list, the order of which can readily be changed with no real effect. It is the second of these that is an interchang-ical order, which like alphabetical order, is not concerned with how the individual letters are formed, but with how different letters are organized sequentially.

And so, getting back to my main point, it seems clearly better to use distinctive elements of the interchange to name them, as opposed to what is an essentially random labeling. I mean, as it stands a mnemonic used to distinguish A4 and B4 parclos is "ahead" and "beyond," which would work well enough if "after" and "before," at least to me, didn't come to mind that much more readily.

[jakeroot]

This is my thought on how parclo's should be named or numbered:

A6: loop After, six ramps
B6: loop Before, six ramps.

The "4" comes into play, I believe, because four quadrants of the interchange are being used, with other terms like "A3" used to describe parclos with ramps in only three quadrants. Seems to me that the number could just be a representation of the total number of ramps (ideally generalized, if there is some collector/distributor lanes at play).

I would agree that "after" and "before" are the most logical representations of the lettering. "Parclo" is lackadaisical enough that I really don't think A and B need to necessarily represent numerical ordering. That seems needlessly technical.

[kphoger]

This is my thought on how parclo's should be named or numbered:

A6: loop After, six ramps
B6: loop Before, six ramps.

The "4" comes into play, I believe, because four quadrants of the interchange are being used, with other terms like "A3" used to describe parclos with ramps in only three quadrants. Seems to me that the number could just be a representation of the total number of ramps.

Both systems have their problems.

For example, using your thought method, the interchanges below would both be ParClo A4.

[johndoe]

I've heard "people in the know" use the "ahead and beyond" that CtrlAltDelete mentioned, but in my head the easiest way to remember is that you're either accelerating to the freeway or braking off the freeway.

On the other hand, other "people in the know" just say "parclo" and don't worry about the letter or number.  So if that makes you feel better...as a roadgeek you're ahead of many professionals =)

[jakeroot]

This is my thought on how parclo's should be named or numbered:

A6: loop After, six ramps
B6: loop Before, six ramps.

The "4" comes into play, I believe, because four quadrants of the interchange are being used, with other terms like "A3" used to describe parclos with ramps in only three quadrants. Seems to me that the number could just be a representation of the total number of ramps.

Both systems have their problems.

For example, using your thought method, the interchanges below would both be ParClo A4.

I see, good point!

I've heard "people in the know" use the "ahead and beyond" that CtrlAltDelete mentioned, but in my head the easiest way to remember is that you're either accelerating to the freeway or braking off the freeway.

On the other hand, other "people in the know" just say "parclo" and don't worry about the letter or number.  So if that makes you feel better...as a roadgeek you're ahead of many professionals =)

Are the terms "A4" and "B4" even used professionally?

[johndoe]

Are the terms "A4" and "B4" even used professionally?

I'm sure every consultant / DOT / region has their own terminology but it's very rare for me to hear it.  I think mostly you'd hear something like "here are the estimated costs for the SPUI vs parclo".

[jakeroot]

Are the terms "A4" and "B4" even used professionally?

I'm sure every consultant / DOT / region has their own terminology but it's very rare for me to hear it.  I think mostly you'd hear something like "here are the estimated costs for the SPUI vs parclo".

I see. Roadgeeks being roadgeeks, coming up with our own terms. Gotta wonder who first coined those terms to begin with, since they're all over Wikipedia and this site (althoug, granted, "parclo" is probably more common than being super specific).

[SeriesE]

Here's an A4 in Taiwan: https://www.google.com/maps/@24.9094053,121.1648755,16.93z

[tradephoric]

Choose a Parclo B4 before a Parclo A4.

[kphoger]

B4 before

I see what you did there.

[jakeroot]

Parclo A4 in Japan:

https://www.google.com/maps/@35.1211478,138.8809525,622m/data=!3m1!1e3

Visually looks like a B4, but is in Japan so RHD.