Talk:Stack interchange

Five-level stacks
"Five-level stacks may have the same configuration as four-level stacks, except that service roads may constitute the fifth level, often being placed at or below grade."

This claim needs a citation and I have noted it as such. I think that some potentially 5-level stacks, such as the Tom Moreland Interchange in Atlanta (this is the one I had in mind), might not meet this criterion depending on the positioning of the service road. Of course, I could be wrong about this, but a referenced source should settle the matter. :) toll_booth 20:00, 3 February 2007 (UTC)

Geographic Areas Featured
Why are these specific areas mentioned? Ontario? Argentina? Great Britian? Seems kind of arbitrary to me. --151.197.169.119 03:41, 2 March 2007 (UTC)


 * At the moment, there aren't many examples; but should it turn into a slipper slope of amassed locations, then I'd be fine with axing them all unless notable for a specific reason. --Thisisbossi 04:48, 2 March 2007 (UTC)


 * If these places are the pioneers of these interchange forms, isn't that a good reason to keep them in the article even after others are built?


 * Is clovestack a typo or a real name?


 * Wanderer57 21:10, 1 November 2007 (UTC)


 * I changed the spelling. Wanderer57 (talk) 22:13, 27 November 2007 (UTC)

Dual-carriageway
I think an explanation of the term "dual-carriageway" would be helpful. I think it is a British term, not understood in North America. (Don't know if it is used elsewhere.) Wanderer57 (talk) 01:14, 20 January 2008 (UTC)

Cloverstack
The entry for "M62 Motorway" states that Junction 10 (with M6) is a cloverstack junction, but this is not mentioned in the list of such junctions for this entry. —Preceding unsigned comment added by 81.102.73.190 (talk) 21:23, 28 February 2008 (UTC)

Proposals for a major rewrite
This article has some issues which I think should be addressed through a substantial revision. In the interests of giving people maximum opportunity to give input or express objections, I'm summarizing them here. For simplicity in the descriptions below, terms like "left-turning" etc. assume traffic circulates on the right:
 * 1) "Stack" is a road enthusiast's term. I have never seen it in official documentation, although officially sanctioned terms (e.g., turban) do exist for certain types of multilevel freeway interchange.  Among road enthusiasts, "stack" also has two distinct meanings, which aren't adequately differentiated in the article.  The narrower meaning refers to an interchange having four or more levels in which all the left-turning movements are served by semidirectional direct connectors which do not cross in plan and are therefore arranged in a Maltese cross configuration.  (Some stacks of this kind are irregular, though--cf. the Wetzlarer Kreuz in Germany or the M4/M25 interchange at Iver near Heathrow Airport.)  The broader meaning refers to interchanges of two or more levels where some movements are not served by simple link or loop ramps, and therefore can include turbans, fully-directional interchanges, "cloverstacks" ("cloverstack" itself being a road enthusiast's term), etc.  In professional circles, a Maltese cross stack is often referred to as a "fully directional interchange with semidirectional direct connectors," "fully directional" meaning that all left-turning movements are served by direct connectors and "semidirectional" meaning that the direct connectors leave and join on the right-hand side of each freeway.  But technically this description can also fit turban interchanges, which are occasionally built as less expensive alternatives to Maltese cross stacks because they have less structural content, but cannot accommodate as much traffic at a given level of service because their connectors have tighter radii.
 * 2) It should be made clearer that a Maltese-cross interchange can be described as a "four-level stack" even if the geometry is such that only three levels cross in plan at any one point.
 * 3) Stacks with included service roads and managed lanes can still fit in the basic Maltese cross configuration. Also, I would contend that service roads should not be counted as part of the freeway since they themselves do not normally have full control of access (though in the case of the IH 10/BW 8 stack near Houston, the frontage roads are also grade-separated).  Therefore, I think the distinction among four-, five-, and six-level stacks should be minimized in favor of language explaining that these all fit into the basic Maltese cross pattern.
 * 4) There should be expanded and more specific discussion of the economic and other logistical variables which influence choice of an interchange type, with more reference to real-world examples. There is now free (public?) access to articles in Proceedings of the Institution of Civil Engineers which explain the rationales for choosing Maltese cross stacks at Almondsbury and Iver in the UK, and there is also a design study for the I-10/Loop 303 interchange in Arizona which compares the costs and benefits of two types of Maltese cross stack and a turban.  It is even possible nowadays to find online the construction plans for both the original Four Level interchange (US 101/California SR 110) and the I-10/I-405 interchange in Los Angeles; these two interchanges show contrasting philosophies of stack construction.  The online knowledge base has moved on considerably since Kurumi's interchange dictionary, and this article should reflect those developments.
 * 5) Since the Maltese cross is the "Queen of Interchanges" and there are relatively few examples worldwide (almost certainly fewer than 100, with a majority in the USA), it would be worthwhile to attempt a complete list of them all, with Google Maps/Wikimapia links to each plus possibly a link to a Google Earth *.kml file with location placemarks. (I am still working on a complete list, but so far I know for sure that there are Maltese cross stacks in the USA, Canada, Australia, China, Britain, Spain, Germany, and Venezuela.)
 * 6) I have not been able to confirm the claim, made in the article, that stacks exist in Buenos Aires. The only stacks I see there (in Google Earth) are variants of the turban or directional interchange.  These qualify as stacks under the loose definition, but not as Maltese crosses.  Argatlam (talk) 14:12, 8 April 2008 (UTC)
 * I have a book about driving from the 1960s that describes what we might call a stack interchange as an "all-directional interchange" (I believe that's the term, I'll get the book out and check it this weekend). Perhaps we should move the article to something like that. The article as it stands really needs more references, too. (Welcome to Wikipedia, by the way.) —Scott5114↗ [EXACT CHANGE ONLY] 16:13, 8 April 2008 (UTC)

Comments re Major Rewrite
This is from the POV of having no technical knowledge of the subject.


 * The article as it stands is dense in terminology and thus somewhat difficult to read (for a layman)


 * The discussion of a proposed rewrite introduces more specialized terms. No objection to these but since this is a "general" encyclopedia it would be good if they are introduced and explained carefully (not just relying on people clicking links to find out what the terms mean - With a complex subject as this is, clicking links can send people on a wild goose chase, IMHO.)


 * The two images are a great help. More images to illustrate other points would help I think.  (I rearranged the images so they are not side-by-side, which I think made the text between them very narrow and hard to read.)


 * International differences in terminology are a complication and it might be very useful if they were given in a conversion table. Eg, I think dual carriageway is the British term for a divided highway. (Or divided highway is the Canadian term for a dual carriageway, depending how one looks at it.) Is the Australian term different? Are there other terms in use?


 * I think it would help understanding of stacks and improve readability to talk a bit about cloverleaf exchanges (and possibly simpler interchanges), which are much more familiar to most people, and also give an idea what problems of cloverleafs lead to the building of stack exchanges.

Interesting topic. Hope these notes are some use. Wanderer57 (talk) 16:29, 8 April 2008 (UTC)
 * Well, we do have an article on cloverleaf interchanges, so while we may note there are problems with the cloverleaf design that make stacks preferable in some cases, we should try and keep from being redundant with that article. —Scott5114↗ [EXACT CHANGE ONLY] 17:53, 8 April 2008 (UTC)


 * The idea was just to give a bit of context to the stack interchanges. I imagine a lot of people will never have seen one.  Cheers, Wanderer57 (talk) 20:42, 8 April 2008 (UTC)
 * Well, just about every major American city has at least one or two (even if people don't know or care about the different types of interchanges), and complex interchanges often become named landmarks in their own right (like the Fort Smith Junction). I'm not sure how common they are in other countries, though. —Scott5114↗ [EXACT CHANGE ONLY] 20:50, 8 April 2008 (UTC)
 * There are somewhat less common, but still numerous. A list would be impractical and would take up too big a part of the article. Admiral Norton (talk) 20:51, 11 April 2008 (UTC)
 * If my comments aren't useful, just ignore them. Wanderer57 (talk) 15:41, 12 April 2008 (UTC)

Here's a hard one for ya...
the I-275/I-471 Interchange in Northern Kentucky(Google Maps). It's very clearly BASED on a four level stack, but modified such that it eliminates almost all of the actual stacking, replacing it almost entirely with simple grading. The basic layout is more or less the same, except that the inner ramps all exit from and merge into the left side of their respective highways, and that each of the two highways has a bow-out in one side to spread them apart. The net effect being that 'stacking' only occurs at four points: two three-level(ramp over highway/ramp merge over highway/ramp split) and two two-level (Highway over Highway). At all other points, all eight ramps and both highways are on the ground. Heavily graded/excavated ground, but ground. It also reduces six of the ramps to being both short and fairly direct. Only the 275->471 ramps end up being long.

So how do you classify this...thing? It's clearly based on some of the idea and flow-paths behind a stack, but was deliberately designed to avoid the actual stack(presumably to save money on all the bridges). It's also HUGE, spreading the highways that much really eats up the real estate, so it's larger than a real stacked interchange would be. Granted, that part of Northern Kentucky was fairly sparsely populated at the time they built it; the real estate very well could've been cheaper than all the bridges would've been. This seems especially likely given that the 275/I-75 interchange a few miles down the road (Google Maps) actually IS a plain vanilla four level stack. They again use as much grading as possible, but right smack dab in the middle, ramps, highway, highway, ramps.

Something to ponder. -Graptor 208.102.243.30 (talk) 08:02, 18 August 2009 (UTC)

Flyover =? on-ramp =? overpass ??
Please define this term in words or label a picture with the term and arrows showing the extent of the object. 'flyover' is not a term used in California, for example, so its use is confusing. --Ancheta Wis   (talk  &#124; contribs) 01:04, 2 November 2012 (UTC)


 * Agree, the targets of onramp and offramp have been modified within the WP:SOURCES by ignoring exitent facts like map material. For Flyovers, I recommend you refer the DOTs publication and to lookup in the map of Singapore also, to see what a flyover is. While focussing on the center of WP:SOURCES, the article's content had more information before, click "view history", but some sources has been rated from primary to unaccetable. The result: old mainstream publications only are in the article. Expensive books or never knowledge and exiting facts are faded out. I recomend to see the articles history, but give the old information a critical review. --Hans Haase (talk) 09:41, 4 June 2014 (UTC)

refs
http://www.ite.org/membersonly/itejournal/pdf/JKA85A24.pdf --Hans Haase (talk) 09:25, 4 June 2014 (UTC)

Not menioned
What about the Turcot Interchange, which is not mentioned. Peter Horn User talk 15:48, 30 November 2015 (UTC)
 * The Wetzlarer Kreuz might be noteworthy as the only fully built stack interchange in Germany. --84.162.197.121 (talk) 00:13, 28 February 2016 (UTC)

Inclusion of three level cloverleaf interchanges
Three level partial cloverleaf interchanges are not stack interchanges and information about them in Alberta is not necessary here; this message serves as notice to prior to a request being made at WP:AN3. -- Ace*YYC 01:45, 17 January 2021 (UTC)


 * Stated that these Alberta examples are close to but not enough to be considered full stack interchanges. Similar reason why the Highway 401-403-410 interchange is mentioned as well as it would have been a full stack had there been a semi-directional ramp instead of the NE quadrant loop ramp.
 * As per above, we can also mention why the Turcot Interchange is not a proper stack interchange although frequently described as one. FobTown (talk) 16:36, 17 January 2021 (UTC)
 * They're just not needed here. Frankly, the problem with these articles is that they always have too many examples. Everyone assumes we need to create some sort of index to every interchange or intersection of a specific type, when all we need is a few illustrative examples to give a reader an idea of what a stack interchange looks like. Beyond that, it's just filler that no one will read.  Imzadi 1979  →   18:22, 17 January 2021 (UTC)
 * Concur with AceYYC and Imazadi1979. No need to pad this article with laundry lists of interchanges that are not true stacks. --Coolcaesar (talk) 06:35, 18 January 2021 (UTC)