Parclo/SPUI hybrid

[tradephoric]

The interchange of I-94 & Sheyenne Street is being constructed in West Fargo.  It's a mix between a Parclo and a SPUI.  Are there other examples of interchanges like this?

[jeffandnicole]

This is why design decisions shouldn't be made after last call is announced at the bar.

[tradephoric]

This is an interesting Parclo A4 interchange at I-95 & Okeechobee Rd in Florida.  It's designed with distributor lanes so that traffic entering the freeway along the arterial doesn't have to drive through any traffic signals.  Would a Parclo A4 SPUI interchange accomplish the same operational benefits as the current configuration?


https://www.google.com/maps/@27.4159481,-80.3883966,586m/data=!3m1!1e3

[tradephoric]

This is why design decisions shouldn't be made after last call is announced at the bar.

LOL the best decisions in life are made after last call (said nobody ever).

[Roadsguy]

This is an interesting Parclo A4 interchange at I-95 & Okeechobee Rd in Florida.  It's designed with distributor lanes so that traffic entering the freeway along the arterial doesn't have to drive through any traffic signals.  Would a Parclo A4 SPUI interchange accomplish the same operational benefits as the current configuration?


https://www.google.com/maps/@27.4159481,-80.3883966,586m/data=!3m1!1e3

Otherwise known as a six-ramp SPUPClo.

[jeffandnicole]

What roadsguy drew was what I was thinking would be better.

The original design isn't bad...but it seems to needlessly add a signal phase on the local roadway.

[kurumi]

^ At first I thought, "no, that's wrong, that's not I-95 at Okeechobee Boulevard" but I was wrong -- after all, FL 70 != FL 704

[jakeroot]

This is an interesting Parclo A4 interchange at I-95 & Okeechobee Rd in Florida.  It's designed with distributor lanes so that traffic entering the freeway along the arterial doesn't have to drive through any traffic signals.  Would a Parclo A4 SPUI interchange accomplish the same operational benefits as the current configuration?

https://i.imgur.com/OmEGEDO.jpg
https://www.google.com/maps/@27.4159481,-80.3883966,586m/data=!3m1!1e3

I don't see anything wrong with the A4 with bypass lanes, assuming the pedestrian crossover points are well designed. Which they seem to be. If there were any pedestrian crossings over the main road, I think it would be better to keep the loop ramp access protected by the off-ramp signals.

As for the Spupclo, seems like you could easily modify any Parclo with enough central ROW into one, without having to modify the ramp design.

[kalvado]

The biggest point of SPUI, as far as I understand, is the ability to have two left turns running sisimultaneously.  Not really the case here, as there are no two separated left turns to being with. Moreover, if ramps converging at the point are spread further out, pattern wouldn't really change. So the only feature of SPUI I see here is wide expensive overpass....

[froggie]

Regarding the interchange in the OP, a few things to point out:

- The existing interchange is a 5-ramp parclo.  The extra loop is for WB 94 to SB Sheyenne St, but is not free-flow....it's tied into the WB ramp signal.

- Ramp traffic heavily favors movements to/from the east.  This, plus the presence of the Sheyenne River in the northeast quadrant and generally having adequate ROW already for the plan is why they went with the planned design instead of an A4.

- Currently, traffic on Sheyenne St has two traffic signals at the interchange.  The planned design has a single signal for southbound Sheyenne traffic only.  That signal will basically be a 3-phase signal.

[tradephoric]

The biggest point of SPUI, as far as I understand, is the ability to have two left turns running sisimultaneously.  Not really the case here, as there are no two separated left turns to being with. Moreover, if ramps converging at the point are spread further out, pattern wouldn't really change. So the only feature of SPUI I see here is wide expensive overpass....

Referencing the picture with the proposed red/yellow ramps... there are two left turns exiting the freeway that would run simultaneously.    The advantage of the single point Parclo is that left turning traffic exiting the freeway would not be conflicting with arterial traffic entering the freeway.  The existing I-95 & Okeechobee interchange does allow arterial traffic to enter the freeway without having to pass through any traffic signals, but that's only because the arterial was designed with distributor lanes (which is definitely not a typical Parclo A4 design).

[tradephoric]

If you have a single-point Parclo B4 interchange, the arterial traffic turning left onto the freeway would closely resemble a super-street design.  With a single-point Parclo B4 there is no longer the added benefit of contraflow left turn lanes along the arterial like seen in the SYNCHRO model below:

https://www.youtube.com/watch?v=ZZZOBPyHuCM


I do love the Parclo B4 interchange because it essentially turns the arterial into a super-street capable of perfect signal progression.  This is easy to visualize if you imagine a single-point Parclo B4.  The biggest disadvantage of a super-street is that side-street traffic can't continue straight through the intersection.  Of course this isn't a problem at an interchange since freeway traffic can be easily diverted so that all off-ramp traffic has a simple right hand turn onto the arterial. 

[johndoe]

Some more discussion and a video are available in this thread: https://www.aaroads.com/forum/index.php?topic=19105

[formulanone]

^ At first I thought, "no, that's wrong, that's not I-95 at Okeechobee Boulevard" but I was wrong -- after all, FL 70 != FL 704

I think "Okeechobee Trafficway" is the only road moniker missing from southern Florida. 

[sparker]

This is why design decisions shouldn't be made after last call is announced at the bar.

That was pretty much my speculation a couple of years back regarding the selection of the I-87 designation in NC/VA (an open bar at the Des Moines SCOURN meeting that spring)! 

[kphoger]

Some more discussion and a video are available in this thread: https://www.aaroads.com/forum/index.php?topic=19105

Mods:  I suggest a thread merge.