The yin-yang interchange?

[Billy F 1988]

Rob Morosi - "The SPUI design is much safer, because of longer exit ramps with increased storage that eliminate the backup on the freeway. And when you exit I-94 to Telegraph, with the SPUI design, the decision of which direction you want is made on the ramp, at a slower speed. Before, that decision was made on mainline I-94 itself.”



Way to prevent backups onto the freeway...

That looks ridiculous. Cut the yin-yang interchanges completely, especially this kind and just make some sort of interchange that will allow for a better flow of inbound and outbound traffic. Case in point would be this very interchange itself. SPUI's won't necessarily help with this problem.

Montana does not have the yin-yang interchanges and for one damn good reason, too. Imagine if I-90 and I-15 had this. What a mess that'd be. Or let's say US 12 and 93 in Lolo had this. Yeah. Not quite the smartest road engineering in my opinion.

[Kacie Jane]

Montana does not have the yin-yang interchanges and for one damn good reason, too. Imagine if I-90 and I-15 had this. What a mess that'd be. Or let's say US 12 and 93 in Lolo had this. Yeah. Not quite the smartest road engineering in my opinion.

Huge flaw in your logic.  I-90/I-15 are two separate three-way interchanges.  This yin-yang is a four-way interchange.  If you tried to apply the yin-yang on either side of Butte, it would really just resolve back into a trumpet -- although it may look more like this thing in New York with the trumpet part in the median.

And US 12/93 in Lolo?  That's a signalized intersection with a two-lane road.  And ignoring the McDonald's on the other side, also a three-way.

The real reason Montana doesn't have any yin-yang double trumpets or whatever you want to call them?  They don't have the traffic counts to warrant hyper-engineered designs.

[Billy F 1988]

Montana does not have the yin-yang interchanges and for one damn good reason, too. Imagine if I-90 and I-15 had this. What a mess that'd be. Or let's say US 12 and 93 in Lolo had this. Yeah. Not quite the smartest road engineering in my opinion.

Huge flaw in your logic.  I-90/I-15 are two separate three-way interchanges.  This yin-yang is a four-way interchange.  If you tried to apply the yin-yang on either side of Butte, it would really just resolve back into a trumpet -- although it may look more like this thing in New York with the trumpet part in the median.

And US 12/93 in Lolo?  That's a signalized intersection with a two-lane road.  And ignoring the McDonald's on the other side, also a three-way.

The real reason Montana doesn't have any yin-yang double trumpets or whatever you want to call them?  They don't have the traffic counts to warrant hyper-engineered designs.

Flaw logic, yes, but I'm just pointing out why MT doesn't have them anyway. That in itself, plus, in you mentioning the traffic count, that's essentially a good thing because most of the interchanges on Interstates 15, 90 and 94 are diamonds, inverted wing or folded diamonds, and the crossover like those in Butte at the 15/90 and Billings at the 90/94 interchange. The yin-yang interchange wouldn't fit anyway.

[InterstateNG]

You'll pardon my presumption, but I quetion how familiar you are with the area surrounding the interchange.

You'll agree with me that a SPUI was a bad design for this interchange.

Nope, sorry.

If you look at the photograph, there's no traffic south of I-94 on southbound Telegraph.  I sincerely doubt it is due to an accident at a cross street, or on Telegraph for that matter.

My educated guess, just a guess, as someone who frequently drove through that area and can't recall a backup on like that, was that a bunch of traffic was using 94 W to 24 S to avoid some sort of perpetual construction on I-75 downriver instead of heading all the way out to 275, given the date of the imagery.

Most of the other historical imagery on Google Earth shows a minimal backup.  And here's Bing's contribution:  http://binged.it/136cGab

[tradephoric]

I'm sure you'll pardon your educated guess, but the backup in the aerial was due to WB I-94 to NB Telegraph being barricaded off (possibly rehab work) forcing all WB traffic exiting the freeway to turn left.

It appears that the traffic signal timing wasn't adjusted to adapt to the changing traffic volumes during the rehab work leading to backups on the off-ramp.  The argument can be made that the timing should have been adjusted and this backup never would have occurred.  While I do agree, government agencies aren't going to be able to react to every possible scenario that might pop up, as efficient as they may be.  What happens when the signal is stuck in flash and there's a jackknifed semi on one of the off-ramps?  I like designs that are able to manage on their own when the proverbial SHTF.  Unfortunately the SPUI doesn't manage so well when something gets thrown at it.

As an alternative freeway-to-arterial interchange, consider the Folded Interchange. 

With the Folded Interchange, all traffic exiting the freeway makes a right-hand turn onto the arterial.  Off-ramp traffic is permitted to make a right-turn-on-red reducing the potential for backups onto the freeway.  The potential for gaps in traffic along the arterial is increased by the fact that arterial left-turners entering the freeway are rerouted before the off-ramp intersection, reducing the total traffic volumes traveling through the off-ramp intersection.  Also, by rerouting the left-turners it increases the amount of storage space available reducing the likelihood of left-turners backing up into the arterial thru lanes.  Finally, the traffic signals along the Folded Interchange only stop one-direction of travel along the arterial making perfect progression possible regardless of signal spacing. 

This interchange wouldn't have been the most practical choice for I-94 & US-24 as it would have required Telegraph to be widened quite extensively leading to a longer bridge span.   In terms of efficiency, however, it's probably the most efficient freeway-to-arterial interchange that has yet to be built.

[pianocello]

That looks kinda like a stretched-out version of the six-ramp spupclo

[InterstateNG]

So the SPUI is a poor choice because of some hypothetical that would mess up any interchange type.  Got it.

And with that, I'm through debating with our resident one-note parclo fetishist.

[tradephoric]

See, I knew he'd come around and agree that the SPUI was a poor choice!

[vtk]

Can anyone design an interchange based on this?





Tradephoric, this "folded" interchange looks nice, but it's not a universal solution.  Many cities don't follow a mile-grid pattern, so they don't really have any good signal progression to mess up.  Also, check out this Parclo B4 which has the same "signals stop only one direction of traffic" property which you so highly proclaim: US 52 and US 63 on Google Maps; it's almost like a mirror image of your folded interchange, actually.  And I think you missed the point of InterstateNG's last post.

[tradephoric]

Tradephoric, this "folded" interchange looks nice, but it's not a universal solution. 

It's not universal at all considering none have been built.

Many cities don't follow a mile-grid pattern, so they don't really have any good signal progression to mess up.

Any potential for improved signal progression along an arterial is beneficial regardless of what grid-pattern is present.  The more traffic signals that stop only direction of travel along an arterial, the more likely good progression can be achieved. 

Also, check out this Parclo B4 which has the same "signals stop only one direction of traffic" property which you so highly proclaim: US 52 and US 63 on Google Maps; it's almost like a mirror image of your folded interchange, actually.

That's a Parclo A4 with looped windmill ramps.  I like the design but my concern is under low visibility conditions or snow covered roads, the driver turning left from the off-ramp might get a green light and assume they are allowed to cut over to the right-most lane of the arterial.

And I think you missed the point of InterstateNG's last post.

Someone waiting to turn left at a red light is delayed until they get a green regardless of how many gaps in traffic there are... even at 4 AM you got to wait for the green light or just hope there isn't a cop around.  Someone waiting to turn right who is permitted to turn right-on-red is only delayed until an available gap in traffic is present.  This is a real simple concept that InterstateNG apparently doesn't understand.  The Folded interchange could handle these hypothetical scenarios better than the SPUI since all traffic coming off the freeway in a Folded Interchange design can turn right during gaps reducing the likelihood of backups onto the freeway (keeps the off-ramp traffic clearing).

[Revive 755]

Tradephoric, this "folded" interchange looks nice, but it's not a universal solution.  Many cities don't follow a mile-grid pattern, so they don't really have any good signal progression to mess up.  Also, check out this Parclo B4 which has the same "signals stop only one direction of traffic" property which you so highly proclaim: US 52 and US 63 on Google Maps; it's almost like a mirror image of your folded interchange, actually.  And I think you missed the point of InterstateNG's last post.

So in addition to having drivers try to merge while not violating the downstream signal or rear ending an already stopped vehicle, there's the joy of having vehicles merging on both the left and right sides at the same time (which works really well on NB US 41 at the IL 120/IL 43 interchange) [/sarcasm]  Might work if the traffic volumes there are low enough, but it might need a redesign if the volumes increase.

There is a half version of that design for I-355 at Army Trail Road in Illinois:
https://maps.google.com/maps?q=Addison,+IL&hl=en&ll=41.931624,-88.031012&spn=0.003372,0.008256&sll=41.932973,-88.037294&sspn=0.003372,0.008256&oq=add&t=k&hnear=Addison,+DuPage,+Illinois&z=18

[national highway 1]

Here's a similar interchange in Singapore:
http://goo.gl/maps/WSoaJ

[US12]

You'll pardon my presumption, but I quetion how familiar you are with the area surrounding the interchange.

You'll agree with me that a SPUI was a bad design for this interchange.

Sorry, but I don't.

Considering the main goal of narrowing the I-94 ROW to normal freeway grade and that we are dealing with an arterial, not a freeway...the SPUI design works perfectly for me. How do you know the backup isn't due to an accident on the cross street???  Plus, temporarily lengthing the left turn traffic cycle for the oncoming exit ramp traffic (or, simply the use of a traffic cop) resolves that  backup easily.

If you look at the photograph, there's no traffic south of I-94 on southbound Telegraph.  I sincerely doubt it is due to an accident at a cross street, or on Telegraph for that matter. 

If you look  on Google maps and zoom in the I 94 West to US 24 North ramp is closed due to construction. You can make out the arrow board and construction barrels.

[haljackey]

I based this design for a junction in SimCity 4. Have a look.



Click for full size too!
http://www.majhost.com/gallery/Haljackey/Interchange/drawing-3fixed.png

[kphoger]

This is functionally quite similar to this one near Culiacán, Sinaloa, but not quite the same.

[tradephoric]

I agree that the left entrance/exit ramps are less than ideal in this design.  Likely, this alone will prevent this type of interchange from gaining popularity. 

Then again... when driving along 501 in the Myrtle Beach interchange or along Telegraph in the Detroit interchange, all exiting and entering points are made from the right lane.   I agree it's less than ideal to have a trucker doing 60 on a freeway having to merge over to the left most lane to take an exit off the freeway, but as long as the arterial is the one that widens out to accommodate the loops ramps and not the freeway, this isn't an issue.

[kphoger]

Can anyone design an interchange based on this?

I would be curious to see what the free-floating circles would represent in a highway interchange.