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Author Topic: History of the Parclo Interchange  (Read 2731 times)

jakeroot

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History of the Parclo Interchange
« on: September 24, 2014, 04:58:10 PM »

On Wikipedia (hmm), editors have listed the parclo interchange as having been invented by the Ontario Ministry of Transportation. Now, I had no argument against that, until a few good hours of looking around historic aerials turned up numerous parclos that were built with I-5 near Seattle during the early 60s.

My question is: Did the Ontario MOT actually invent the parclo? And if so, when? I always thought it was invented in the 80s or something but that clearly isn't the case.

I know the Macdonald-Cartier freeway was completely rebuilt during the 60s and 70s with what appears to be parclos but I can't tell.

Oh, and if you forgot what a parclo interchange was:

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NE2

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Re: History of the Parclo Interchange
« Reply #1 on: September 24, 2014, 05:29:49 PM »

Ontario probably claims to have invented it, and enough other sources have sucked their dick that you'll have a hard time keeping this factoid out of the Kipe.
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Roadrunner75

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Re: History of the Parclo Interchange
« Reply #2 on: September 24, 2014, 08:44:19 PM »

There were partial cloverleaf interchanges in NJ in the 1950s at least.  The section of I-295 in Gloucester County with the tight almost RIRO interchanges are from the 50s ("B2" type).  The section of 295 in Camden County has some "A4" types from the early 60s - probably designed in the 50s as well. 
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NE2

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Re: History of the Parclo Interchange
« Reply #3 on: September 24, 2014, 09:08:52 PM »

There were partial cloverleaf interchanges in NJ in the 1950s at least.  The section of I-295 in Gloucester County with the tight almost RIRO interchanges are from the 50s ("B2" type).
These are folded diamonds rather than typical parclos. The Merritt Parkway had these in the late 1930s.

The Henry Hudson Parkway at 79th Street is a rather typical 6-ramp parclo from 1937, though with both loops to the east. The Belt Parkway at Cropsey Avenue is another 6-ramp with a bridge date of 1941.
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tradephoric

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Re: History of the Parclo Interchange
« Reply #4 on: September 24, 2014, 10:02:58 PM »

Does an interchange like this exists anywhere?  It's a hybrid of a Parclo/DDI.


http://www.ite.org/meetings/2009TC/Session%2015_%20Keith%20Riniker.pdf
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NE2

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Re: History of the Parclo Interchange
« Reply #5 on: September 24, 2014, 11:27:07 PM »

Does an interchange like this exists anywhere?  It's a hybrid of a Parclo/DDI.

http://www.ite.org/meetings/2009TC/Session%2015_%20Keith%20Riniker.pdf
Since opposing directions don't cross each other, it's more like a parclo/SPUI hybrid. Or a spupclo. This is exactly like putting two trumpets next to each other with the appropriate through connections. It wouldn't surprise me if there's one somewhere; I've seen a few diamonds half-SPUIed in this fashion.

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cbeach40

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Re: History of the Parclo Interchange
« Reply #6 on: September 25, 2014, 12:49:37 PM »

There are so many things wrong with that Wikipedia article. Such as:
- it was not developed to replace cloverleaf interchanges, there were many years where we built both types, before giving up on 8-ramp cloverleaf interchanges around 1963
- "where full grade separation is not required" - full grade separation is required on all freeway crossings, it's kind of what makes them freeways
- the Ministry of Transportation didn't even exist under that name until 1987
- Parclo A designation means the loop is upstream of the crossroad, Parclo B means the loop is downstream of the crossroad. Not sure if this is so much an error or just a clusterfuck of language here
- There's only an A4 Parclo or A2 Parclo (or B), odd numbers are not used. Each side is referred to individually.

Yeah, I'm pretty doubtful there was anything special about its "invention" or if MTO's predecessors were even behind it. It's just a modified cloverleaf.
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jakeroot

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Re: History of the Parclo Interchange
« Reply #7 on: September 25, 2014, 01:45:08 PM »

Yeah, I'm pretty doubtful there was anything special about its "invention" or if MTO's predecessors were even behind it. It's just a modified cloverleaf.

I've always thought the same thing...I didn't really know you could "invent" a modification of the cloverleaf. The parclo is just a move of the ramps. It would seem that there are a pre-specified number of configurations and we are just slowly "discovering" them.
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cl94

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Re: History of the Parclo Interchange
« Reply #8 on: September 25, 2014, 11:14:03 PM »

I don't think there's any real way to determine who "developed" the parclo because it is, by definition, an interchange with at least 1 loop ramp that isn't a trumpet or some variation thereof. If you're talking about an A4 or B4, you might be able to date that to somewhere, but there have been parclos as long as there have been cloverleafs. Quite a few of the New York parkways have them and they were built long before the 1960s. Exit 2 on the Jackie Robinson is an A2, for example.
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