parclo names

[NE2]

Is there a logical system to the names like "parclo A4" and "parclo B2"? Can all designs be unambiguously represented?

[tradephoric]

The letters represent what type of loop ramps are being used:
Parclo A = circular loop ramps enter the freeway
Parclo B = circular loop ramps exit the freeway
Parclo AB = one direction of the freeway has an entering-loop ramp, the other direction has an exiting-loop ramp

The number represent how many quadrants of the interchange have on-ramps and/or off-ramps of some kind or another.

As an example, here is a Parclo B3 interchange:



Here are the main types of variations (don't know why 2 on-ramps are being shown on the SW quadrant of the Parclo A4):

[roadfro]

Another question would be where does this terminology come from?

[Big John]

Another question would be where does this terminology come from?

PARCLO = PARtial CLOverleaf.

A and B are directions compared to the major roadway.  I had not seen the AB term before as I have seen and worked with it being called a Parclo C

[vtk]

The terminology comes from Ontario, which claims to have invented the parclo.

[johndoe]

I always assumed
A=loop gore on main route (A)head of the bridge
B=loop gore on main route (B)eyond the bridge

so the AB versions have at least one ahead and one beyond

[vtk]

The A has loops entering the freeway; the B has loops exiting the freeway.  Where the gore point is relative to the bridge is just a minor geometric variiation resulting from the design standards employed and the angle between roadways.

[johndoe]

The A has loops entering the freeway; the B has loops exiting the freeway.  Where the gore point is relative to the bridge is just a minor geometric variiation resulting from the design standards employed and the angle between roadways.

I just find it easier to remember that way, and it's true about 95% of the time    Maybe it'd be more correct to say the loop itself is ahead/behind the arterial.

[vtk]

Maybe it'd be more correct to say the loop itself is ahead/behind the arterial.

Yes, that would be a more accurate way to put into words what you apparently meant from the start.  Though I think ahead/behind has some potential pitfalls as a mnemonic; if you're standing on the freeway under/over the crossroad, the A parclo has the loop behind you, while the B parclo has the loop ahead of you, and that's backwards.  (It's a silly question of orientation reference: is it my 'ahead', or the interchange's 'ahead', assuming it's facing me?  The latter, if the mnemonic is to work.)  Or it could be corrupted to after/before, which would also be backwards unless you're talking about the position of the bridge relative to the loop.

[haljackey]

Parclo A4. 4 Entrance ramps, 2 exit ramps.



Parclo B4. 2 Entrance ramps, 4 exit ramps.

[NE2]

The letters represent what type of loop ramps are being used:
Parclo A = circular loop ramps enter the freeway
Parclo B = circular loop ramps exit the freeway
Parclo AB = one direction of the freeway has an entering-loop ramp, the other direction has an exiting-loop ramp

So what if there are three loops?

[kphoger]

The letters represent what type of loop ramps are being used:
Parclo A = circular loop ramps enter the freeway
Parclo B = circular loop ramps exit the freeway
Parclo AB = one direction of the freeway has an entering-loop ramp, the other direction has an exiting-loop ramp

So what if there are three loops?

I assume such an interchange would have loop ramps both exiting and entering the freeway, therefore it would be Type AB.  The number refers to how many quadrants there are ramps in.  So I would assume it'd be an AB-4.

[NE2]

So what if there are three loops?

I assume such an interchange would have loop ramps both exiting and entering the freeway, therefore it would be Type AB.  The number refers to how many quadrants there are ramps in.  So I would assume it'd be an AB-4.

Making this naming system ambiguous.

[kphoger]

OK.  Let's name it Marcilene Sullivan.

[hbelkins]

So what if there are three loops?

http://goo.gl/maps/BKRhA

[NE2]

So what if there are three loops?

http://goo.gl/maps/BKRhA

OK...

[vtk]

I don't think the Ontario typology includes designs with weaving on the freeway.

And so what if the type names are possibly ambiguous? Did anyone say they were unambiguous?  If you want an unambiguous categorization scheme of all possible parclo interchanges, come up with one yourself.  Or, actually, I have one; maybe I should post it...

[Alps]

In order to be unambiguous, you'd have to add some stuff. I'm thinking you need to be able to number quadrants. It turns into notation like a chess move, but perhaps more complex.

[roadfro]

Another question would be where does this terminology come from?

PARCLO = PARtial CLOverleaf.

A and B are directions compared to the major roadway.  I had not seen the AB term before as I have seen and worked with it being called a Parclo C

Well I get the "parclo" part, it's the letters and numbers I am curious. As in, is there some "official" document somewhere that gives the definitive explanation of a B4 versus A2 or whatever. Cause NE2 is right, it seems ambiguous without a precise definition of terms.

[empirestate]

This is just my own thinking, but I find there's a distinction to be made between a partial cloverleaf and a folded diamond. In other words, no such thing as a parclo 2, unless it's an incomplete interchange.

I'd argue that a cloverleaf loop serves to eliminate a left-turn movement somewhere, and a true cloverleaf loop always has a partner ramp that isn't a loop (though it may be missing in certain instances). Of course, a full cloverleaf, where we get the name, has 8 ramps, no left turns, with 4 loops and 4 corresponding non-loop ramps.

A partial cloverleaf, then, has less than 8 ramps but, by definition, at least 5, unless there are missing movements. And it has at least one theoretical pair, consisting of one loop and one non-loop, even if the non-loop member of the pair is missing.

A folded diamond, on the other hand, just moves one or more of the straight ramps across the road so that it makes a horseshoe or loop shape. You still have an intersection with the cross road, rather than a taper as you would with a cloverleaf loop. The function of the loop is different: instead of eliminating a turn movement, they often exist simply because of some obstruction in what would be their usual quadrant. I assume there may also be advantages to having a T-intersection instead of a four-way in some applications.

So by my logic, this is a folded diamond, not a parclo: http://goo.gl/maps/O0FXJ
This is a parclo, an A4: http://goo.gl/maps/4AtTI

I can't think of a hybrid parclo/folded diamond, but it would be interesting to find. EDIT: Mere minutes later, I found one, though the hybridity is a couple of levels deep: http://goo.gl/maps/a56Sz

Maybe it'd be more correct to say the loop itself is ahead/behind the arterial.

Yes, that would be a more accurate way to put into words what you apparently meant from the start.  Though I think ahead/behind has some potential pitfalls as a mnemonic...

For the mnemonic, I'd say this:
A = entering (loop ramp enters the freeway)
B = exiting (loop ramp exits the freeway)
Both "A" and "B", and "entering" and "exiting" are in the same alphabetical order. Though I suppose really, they should have chosen N and X instead of A and B!

[Kacie Jane]

This is just my own thinking, but I find there's a distinction to be made between a partial cloverleaf and a folded diamond. In other words, no such thing as a parclo 2, unless it's an incomplete interchange.

Not just your own.  I definitely agree with everything you're saying.

So by my logic, this is a folded diamond, not a parclo: http://goo.gl/maps/O0FXJ
This is a parclo, an A4: http://goo.gl/maps/4AtTI

I can't think of a hybrid parclo/folded diamond, but it would be interesting to find. EDIT: Mere minutes later, I found one, though the hybridity is a couple of levels deep: http://goo.gl/maps/4AtTI

But I would assume you didn't mean to link to the same map twice?

[empirestate]

I can't think of a hybrid parclo/folded diamond, but it would be interesting to find. EDIT: Mere minutes later, I found one, though the hybridity is a couple of levels deep: http://goo.gl/maps/4AtTI

But I would assume you didn't mean to link to the same map twice?

Whoops, fixed that!
http://goo.gl/maps/a56Sz

[johndoe]

Maybe it'd be more correct to say the loop itself is ahead/behind the arterial.

Yes, that would be a more accurate way to put into words what you apparently meant from the start.  Though I think ahead/behind has some potential pitfalls as a mnemonic; if you're standing on the freeway under/over the crossroad, the A parclo has the loop behind you, while the B parclo has the loop ahead of you, and that's backwards.  (It's a silly question of orientation reference: is it my 'ahead', or the interchange's 'ahead', assuming it's facing me?  The latter, if the mnemonic is to work.)  Or it could be corrupted to after/before, which would also be backwards unless you're talking about the position of the bridge relative to the loop.

Yeesh...getting technical here are we?  I mean a person driving on that freeway will see the loop ahead or beyond the crossroad.