text:
Talk:Isosceles trapezoid

"intersect at equal positions"
What does "intersect at equal positions" mean? — Timwi 01:32, 8 Mar 2004 (UTC)

 * A little late, but I think what is meant by this is that the two top sections of the diagonals are congruent, and the two bottom sections of the diagonals are also congruent. All four diagonal sections are not congruent, as can be seen by drawing a tall, skinny isosceles trapezoid. Loggie 01:29, 4 May 2005 (UTC)

A little long to be a stub
Are you sure this is a stub? It seems a little long to be a stub yet too short to be a full-fledged article. --Mannyram24 13:36, 6 April 2006 (UTC)

the problem of parallelograms
The article suggests that a paralleologram is not an isosceles trapezoid. Why? A parallelogram has two parallel opposing sides, and the other two sides are equal to each other. —Preceding unsigned comment added by Honghaier (talk • contribs) 17:15, 13 October 2007 (UTC)

 * In essence the idea is to distinguish between two types of quadrilaterals, namely Trapezoids and Parallelograms. If parallelograms were isosceles trapezoids, then they would have properties like diagonals of the same length, or congruent base angles. Most parallelograms do not have the diagonals of the same length, or base angles congruent unless they are rectangles. In this case, isosceles trapezoids and rectangles do have the same properties. The bottom line: when you write a property of an isosceles trapezoid you are not writing a property of a parallelogram, but a rectangle; so it makes no sense to call parallelograms isosceles trapezoids since the former do not have the same properties of the latter. —Preceding unsigned comment added by 72.178.193.150 (talk) 04:10, 12 August 2009 (UTC)

 * The distinguishing property is the line of symmetry (parallelograms in general don't have one). It remains true that some parallelograms (namely rectangles) are isosceles trapezoids (or trapeziums outside the USA), but a general parallelogram is not. The intersection of the two sets is the set of rectangles.    D b f i r s   11:45, 12 August 2009 (UTC)

 * What makes a trapezoid a trapezoid is not the line of symmetry. Look for a book of geometry and you will see that the line of symmetry is a property, not part of the definition (hence, the definition of the isosceles trapezoid is wrong in this article). What makes a trapezoid such is the fact there are two parallel sides. Some people think that parallelograms should be trapezoids because they satisfy that part of the definition, and sometimes (for some purposes) they both have similar properties (e.g. they are both convex quadrilaterals), but the distinction is necessary when you want to prove properties like base congruent angles, etc. However, what should be clear is that there is no general agreement about if parallelograms are trapezoids. The main point is why would you want parallelograms to be trapezoids. This has to do with theory (e.g. properties that they have). I still fail to see what is the advantage of making parallelograms trapezoids, when parallelograms do not have base congruent angles, so it is a bit of a contradiction (to put it lightly) to prove a theorem like "isosceles trapezoids have congruent base angles" and then say "well, parallelograms are isosceles trapezoids, but unless they are rectangles they do not satisfy the above property about angles". It is better to make a clear distinction and say "trapezoids have only to parallel sides", and this avoids all the problems that you could have with exceptions to some of the properties that trapezoids have but parallelograms do not. —Preceding unsigned comment added by 72.178.193.150 (talk) 03:21, 15 August 2009 (UTC)

 * You seem to be presenting two conflicting views. The definition in the article is designed specifically to preclude the admission of the general parallelogram from the set of isosceles trapezoids (trapeziums), but to include the rectangle.  Why do you think that this definition is wrong?    D b f i r s   08:28, 24 August 2009 (UTC)

There are two schools about what a trapezoid is. It all depends on your needs. From the perspective of a mathematician (as opposed to a lay person), the need is dictated by the theory, not personal preferences, or tradition. In fact, theories have changed a lot through the years. Calculus did not have the form it has until the end of the 19th century, so you can imagine how long it took to put it in the terms that it exists today. Even up to this day, there has not been a traditional book on Calculus that has been studied for centuries, so all corrections that have had to be made to the theory have prevailed over the original attempts.

In constrast, Geometry has had a main book that has determined the tradition over centuries. That tradition was changed at the end of the 19th century and beginning of the 20th century when Hilbert et al. rewrote the theory in Geometry. The new theory in Geometry is written to include the old theory, in other words, all the current knowledge of geometry includes Euclid's books.

The problem that one has with trapezoids is if there are only two parallel sides, or should there be two pairs of parallel sides. Again, think about needs and theory. What are your needs? If you are trying to classify shapes (as in different shapes look essentially different), or if you are trying to write formulas for lengths, areas, etc. and these formulas look too different between quadrilaterals with only two parallel sides, than with parallelograms, and if the former type of quadrilaterals appear too much in your theory, then it is natural to give them a name that distinguish them from the other type of quadrilaterals.

What this all means is that you must judge your need before you create a definition. I can define many things, but only those that are relevant are the ones to be considered. Consider the following chain of definitions and theorems

Definition: A trapezoid is a quadrilateral that has only one pair of parallel sides. The non parallel sides of a trapezoid are called legs.

Definition: A parallelogram is a quadrilateral that has both pair of opposite sides parallel.

Definition: An isosceles trapezoid is a trapezoid, whose legs have the same length.

It is clear from this definition that parallelograms are not isosceles trapezoids.

Ok, now that definitions have been laid out, we can prove theorems. Here are some theorems

Theorem: in an isosceles trapezoid, the diagonals have the same length.

If parallelograms were to be considered isosceles trapezoids, that theorem would be false. In some place in the proof of that theorem one needs to use that isosceles trapezoids are not parallelograms. I will leave that to you to figure out where that is done.

One could reply back and say, wait, Rectangles do satisfy that, they are parallelograms and satisfy that, so why can't I call rectangles "isosceles trapezoids". Again, the point is the need. Do we need to include rectangles in the theory of isosceles trapezoids? Are rectangles trapezoids? not according to the definition given above.

Ok, so let me look at the flip side. Assume that we give the following definition

Definition: a trapezoid is a quadrilateral that has at least two parallel sides.

In that definition, a parallelogram is a trapezoid. Now you want to define isosceles trapezoid, so how do you that? Well, you want to preserve the theorem that in an isosceles trapezoid the diagonals have the same length. You realize that you can not do this by using the length of the other sides, since in most parallelograms, the diagonals have different lengths, so you are forced to make a different type of distinction between quadrilaterals, and that is that they have a specific line of symmetry. What has been done from the perspective of theory, is that you need to create a number of definitions to explain what symmetry means. This includes the idea of perpendicularity, so you need new definitions and criteria in order to distinguish an isosceles trapezoid from within the class of trapezoids. It takes a bigger effort to define an isosceles trapezoid according to this theory, than is necessary. I showed before that it is not necessary. All you need is the concept of parallelism, not of perpendicularity or symmetry.

This should make the first theory preferable over the second.

The only advantage that I have ever seen of using the second definition is that with the second definition you can have the following theorem

Theorem: All trapezoids are convex quadrilaterals.

In the first theory, you have to prove separate theorems for trapezoids and parallelograms. I do not consider that to be a big disadvantage (or one could prove the theorem that "if a quadrilateral has two parallel sides, then it is convex", which includes the trapezoid (in the first sense) and the parallelogram.

I hope this makes sense. —Preceding unsigned comment added by 72.178.193.150 (talk) 15:51, 30 August 2009 (UTC)

 * Yes, it makes perfect sense. It's just that all of the mathematicians I've ever met use inclusive definitions (your second definition) for quadrilaterals.    D b f i r s   11:27, 23 May 2010 (UTC)

 * I don't understand this assertion: In that definition, a parallelogram is a trapezoid. Now you want to define isosceles trapezoid, so how do you that? Well, you want to preserve the theorem that in an isosceles trapezoid the diagonals have the same length. You realize that you can not do this by using the length of the other sides, since in most parallelograms, the diagonals have different lengths.... [emphasis added]
 * A parallelogram with unequal diagonals (i.e. a parallelogram other than a rectangle) is not an isosceles trapezoid, so what's the problem? —Tamfang (talk) 18:42, 24 May 2010 (UTC)

Paragraph moved from article
I've moved the following paragraph from the article: ''An isosceles trapezoid is also a quadrilateral such that the diagonals divide each other into segments of different length that are congruent among each other. In the picture above, this means that if $$AE = DE$$, $$BE = CE$$ and $$AE\not=CE$$, then the quadrilateral is an isosceles trapezoid.'' Whilst I understand what the anon editor was trying to say, I have two issues:
 * 1) the phrase congruent among each other is vague, and so is not good mathematics. The property is also menioned earlier in the article.
 * 2) The condition $$AE\not=CE$$, is not necessary according to our definition.

What does anyone else think?  D b f i r s   08:22, 24 August 2009 (UTC)

 * Well, if you do not like a phrase, improve it; do not remove it. More to the point, the condition $$AE\not= CE$$ is given because trapezoids are not parallelograms. If $$AE = CE$$ (and $$BE = DE$$), then the quadrilateral is a parallelogram, not a trapezoid. This brings me to the main point. The definition of isosceles trapezoid in this article is not the correct one. That definition is a property. More specifically, we can agree to study quadrilaterals that have a line of symmetry as stated in this article, but those are different type of quadrilaterals, not isosceles trapezoids. In other words, if you want to use such definition, do not use it to define isosceles trapezoids. To give a complete answer, an isosceles trapezoid is a trapezoid (as in "a quadrilateral that has only two parallel sides) where the non parallel sides have the same length. We can talk more about it, if you like. —Preceding unsigned comment added by 72.178.193.150 (talk) 14:55, 30 August 2009 (UTC)

 * It is considered improper, on talk pages, to edit the comments of others to reverse the meaning.  D b f i r s   08:26, 31 August 2009 (UTC)

 * I've done as you suggest (with the help of Tamfang).   D b f i r s   08:28, 31 August 2009 (UTC)

 * If AE=CE (and other defining conditions are met) it's a rectangle, which is an isosceles trapezoid and a parallelogram. —Tamfang (talk) 15:50, 30 August 2009 (UTC)

 * See my response above as to why to make isosceles trapezoids not be parallelograms. —Preceding unsigned comment added by 72.178.193.150 (talk) 15:53, 30 August 2009 (UTC)

 * Um, obviously we don't want to define trapezoids as parallelograms, but you haven't stated a reason to define trapezoids in such a way as to exclude rectangles. —Tamfang (talk) 16:33, 30 August 2009 (UTC)

 * Our article on quadrilaterals specifically shows rectangles as a subset of isosceles trapeziums (trapezoids in the USA). I see no reason to exclude rectangles as a subset since rectangles inherit all properties of the isosceles trapezoid.  The current Wikipedia definition of the isosceles trapezoid seems to have been carefully constructed (five years ago) to precisely match the article on quadrilaterals.    D b f i r s   08:08, 31 August 2009 (UTC)
 * The main idea is that trapezoid is the quadrilateral that you obtain when you divide a triangle in two by a parallel line to one of the sides (one is a similar triangle to the original triangle, the other a quadrilateral which is a trapezoid). Point is, the trapezoid was not supposed to be a parallelogram. Parallelograms, instead have a different idea behind them. There is no such thing as a trapezoid that is a parallelogram (or viceversa). Of course, you can define things to your convenience so that rectangles be trapezoids, but what have you gained from it? The theory has not been improved, has been made more confusing. Particularly, for those poor souls that do not really understand what is really going. It seems that I can't win just because you refuse to hear. I wish you had a better reason than what you are giving. Really. I really wished I could learn something other than sometimes you loose because the person in power does not listen. To summarize, the definition is wrong. It leads to more problems than it solves. I am sorry you were not better advised at the time the definition was written. Enough.72.178.193.150 (talk) 02:09, 5 October 2009 (UTC)

 * I see a difference between "If you do this you get a trapezoid" and "A trapezoid is what you get if (and only if) you do this". The definition of a geometrical figure ought to be its properties, not its construction (there's more than one way to construct anything). — Please note that a rectangle can be made from a degenerate isosceles triangle with a vertex at infinity.  —Tamfang (talk) 15:16, 19 October 2009 (UTC)

 * The inclusive definition given in the article (and in the quadrilateral article) is the one that is standard in the UK, but I think American mathematicians avoid the exclusive definition for their trapezoids (our trapeziums). It is probably not important enough to argue about.    D b f i r s   11:27, 23 May 2010 (UTC)

rectangles
I'd support a careful discussion in the trapezoid section about rectangles. As it stands we should acknowledge that rectangles are in a gray area (without decreeing the correct answer). For that matter a triangle might be considered a trapezoid with one side of length zero although I doubt there would be much suport for that.--Gentlemath (talk) 21:15, 7 December 2009 (UTC)

 * Unless all sources agree on "the correct answer" we should not provide one ourselves, rather we should describe both sides of any disagreement that might exist. See WP:NPOV and WP:OR. —David Eppstein (talk) 00:24, 8 December 2009 (UTC)

So you agree with me, thanks! Or maybe not. The article appears reverted although I don't see it in the history. In fact when I look at the article text itself it says:
 * An isosceles trapezoid (isosceles trapezium in British English) is a quadrilateral with a line of symmetry bisecting one pair of opposite sides,
 * making it automatically a trapezoid. Two opposite sides (bases) are parallel, the two other sides (legs) are of equal length.

but when I consider editing it it says:
 * An  isosceles trapezoid (isosceles trapezium in British English) is a quadrilateral with a line of symmetry bisecting one pair of opposite sides,
 * making it automatically a trapezoid. Many sources, but not all, would qualify all this with the exception: "excluding rectangles."

Anyway, is the intention something like: An isosceles trapezoid is a (convex) quadrilateral with exactly one line of symmetry, that line  bisecting a pair of opposite sides? The way it was written one day ago seemed to include rectangles, which are the one class of parallelograms which some would admit as trapezoids. I didn't take a stand one way or another, merely said: some would say 'but not rectangles'. I'll look for a source with the minority opinion. For now I think I will open an edit and then save without doing anything just to see what happens.--Gentlemath (talk) 03:12, 8 December 2009 (UTC)

OK,now the text does include my change. The book The classification of quadrilaterals: a study of definition By Zalman Usiskin, Jennifer Griffin, David Witonsky, Edwin Willmore is viewable on google books. A summary at http://www.mathcurriculumcenter.org/QuadSummary.pdf shows that it discusses the question are rectangles isosceles trapezoids. Some sources (such as the influential text by Moise in foundations of geometry) use an inclusive definition which considers every parallelogram as a trapezoid. More conservatively one could observe that if convex quadrilateral ABCD has sides AB and DC parallel and sides AD and BC congruent then either r angles A and B are congruent (isosceles trapezoid) or else angles A and C are congruent (arbitrary rectangle). The former case can also be characterized as the one in which the figure can be inscribed in a circle. But in the special case of a rectangle both apply. Ultimately it is a matter of convention. In the case it is not clear which convention is to be preferred. --Gentlemath (talk) 03:43, 8 December 2009 (UTC)

 * For what it's worth, my own preference is to be inclusive. It keeps the definitions simpler that way. But I agree that we should let the literature rather than our own preferences guide us here. —David Eppstein (talk) 04:04, 8 December 2009 (UTC)

 * I agree that the inclusion of rectangles is just a matter of convention (and the wording of the definition), but I was under the impression that the vast majority of sources and almost all mathematicians used inclusive definitions. Is this not the case?    D b f i r s   08:13, 9 December 2009 (UTC)
 * I don't actually know. My suspicion is that the distribution of answers would be different if you asked research mathematicians vs if you asked the writers of high school geometry textbooks. —David Eppstein (talk) 08:12, 10 December 2009 (UTC)

One could allow 3 conventions 1) a parallelogram is never a trapezoid 2) rectangles are trapezoids but not other paralleograms are 3) all parallelograms are trapezoids I am fairly sure that almost every current US textbook uses convention 1). So that should maybe be noted to avoid confusing students (hence I would revert the latest change). I personally think 2) makes sense since the main theorem becomes (parallel bases + equal base angles)<=>(parallel bases + equal legs)<=>isosceles trapezoid. Also then every quadrilateral in the trapezoid rule is a trapezoid! Since b-a=0 in this case, some of the formulas (with (b-a)^2 in a denominator) need a fix (cancel out the (b-a)^2 from the numerator). (gentlemath at a public computer) —Preceding unsigned comment added by 131.91.228.172 (talk) 23:08, 9 December 2009 (UTC)

Those (b-a)^2 formulas are in the trapezoid article. —Preceding unsigned comment added by 131.91.228.172 (talk) 23:11, 9 December 2009 (UTC)

 * I think 3) is common in the UK (as at the end of our article on quadrilaterals), but I agree that we need to report differing definitions. I'm surprised that US textbooks use  option 1) - is this just so that they don't have to make an exception to a formula?    D b f i r s   08:08, 10 December 2009 (UTC)

 * I see it differently than what is presented here. The overall set would be Trapezoids (having a pair of opposite sides parallel) to separate it from the remaining quadrilaterals. Then that set is divided into two disjoint sets, Parallelograms and Non-parallelogram Trapezoids (traditional trapezoids). The Non-parallelogram Trapezoid set has the proper subset Isosceles Trapezoid. A rectangle would not be an Isosceles Trapezoid maintaining the oblique nature of "isosceles". However, if you prefer a crossover, it would be no different than saying a square is a kite. Regarding your question on the definition, the answer is most likely inertia. Not enough agreement for texts to change (speculation). I have no idea regarding the situation for advanced geometry texts. JackOL31 (talk) 23:43, 12 December 2009 (UTC)

 * That's an interesting alternative veiwpoint that I hadn't thought of. I suppose that the trapezoid (or trapezium in the UK) is just not important enough to be consistently defined.    D b f i r s   00:19, 13 December 2009 (UTC)

I really regret not being able to participate in this conversation when it originally happened! :) I have recently been doing a lot of research on the trapezoid definition struggle. Of course, like most other mathematicians, I think the inclusive definition is the "right" one, and that the obvious fix for defining an isosceles trapezoid is to use "base angles congruent." The fact that it's not equivalent to "legs congruent" does not seem like a major loss. Rschwieb (talk) 16:19, 21 November 2012 (UTC)

Bad definition
In Euclidean geometry, an isosceles trapezoid (isosceles trapezium in British English) is a trapezoid where the legs have equal length.

Under this definition, a non-rectangular parallelogram would be an isosceles trapezoid. Georgia guy (talk) 18:38, 18 March 2013 (UTC)

 * Yes, see the comment above. It's OK if you define "legs" as non-parallel sides, but then the set of rectangles would not be a subset of the isosceles trapezoids.  The recent change by David Eppstein sorts out the problem.    D b f i r s   22:50, 18 March 2013 (UTC)

Parallelograms again
I gather from the previous discussions on this talk page that isosceles trapezoids must be defined to exclude non-rectangular parallelograms. Currently this article's lead says

 * In Euclidean geometry, an isosceles trapezoid (isosceles trapezium in British English) is a convex quadrilateral with a line of symmetry bisecting one pair of opposite sides.

Not sure, but it seems that this permits parallelograms. The article Symmetry (geometry) says

 * Under an isometric transformation, a geometric object is said to be symmetric if, after transformation, the object is indistinguishable from the object before the transformation, i.e., if the transformed object is congruent to the original.[5]

Doesn't either of the (bimedian) lines bisecting two opposite sides of a parallelogram cut it into congruent pieces? Then the parallelogram is symmetric, and each bimedian is a line of symmetry, so the article's current definition includes parallelograms.

Maybe this could be fixed by changing "line of symmetry" in our definition to "line of reflectional symmetry"? Loraof (talk) 17:34, 9 April 2016 (UTC)
 * A parallelogram that is neither a rectangle nor a rhombus has no lines of symmetry. A line of symmetry (in 2 dimensions) means reflection symmetry. Rotational symmetry is defined by a point, not a line, unless we're dealing with 3-dimensional figures. Georgia guy (talk) 17:43, 9 April 2016 (UTC)

 * Right, our redirect Line of symmetry reflects (ahem) what you say. Loraof (talk) 21:59, 9 April 2016 (UTC)

By the way, the definition of a symmetry transformation quoted above is wrong. The transformed object needs to be equal to the original, not just congruent to it. —David Eppstein (talk) 23:43, 9 April 2016 (UTC)

 * What's the difference between "equal to" and "congruent to"? Loraof (talk) 19:32, 11 April 2016 (UTC)

 * Congruence is precisely defined in Mathematics (see Congruence (geometry), though I expect you already know the definition). "Equal to" is not clearly defined for shapes because one needs to specify which properties are equal.  I've removed the misleading "equal to" in the article, and also the misleading reference to congruence.    D b f i r s   20:58, 11 April 2016 (UTC)

Citation 2 (Referenced under "Special Cases") is inappropriate.
The reference in question excludes rectangles only in that it uses the exclusive definition of trapezoid - rectangles are being excluded because the text does not consider them trapezoids at all (much less isosceles trapezoids). Since Trapezoid defaults to the inclusive definition, I'd assume we'd want to maintain that here. If we want to note that an exclusive definition of isosceles trapezoid excludes rectangles, then we should say that explicitly. It is unclear if that was the intended meaning here, or if this also refers to other definitions that exclude rectangles for whatever reason (in which case, we need citations of those).66.211.251.59 (talk) 19:35, 7 July 2022 (UTC)

title: Talk:Isosceles trapezoid


text:
CityLink

CityLink is a network of tollways in Melbourne, Victoria, Australia, linking the Tullamarine, West Gate and Monash Freeways and incorporating Bolte Bridge, Burnley Tunnel and other works. In 1996, Transurban was awarded the contract to augment two existing freeways and construct two new toll roads – labelled the Western and Southern Links – directly linking a number of existing freeways to provide a continuous, high-capacity road route to, and around, the central business district. CityLink uses a free-flow tolling electronic toll collection system, called e-TAG. CityLink is currently maintained by Lendlease Services.

History
The first mention of a southern and western inner city bypass was in the 1969 Melbourne Transportation Plan. The plan advocated for reservations and set aside sinking funds for the new inner city freeway system. It was one of the few freeways connecting to the inner city (along with the Eastern Freeway to Clifton Hill) which was not later abandoned.

The proposal to build CityLink was first announced in May 1992 and received the State Government's formal approval in mid-1994. The contract was awarded in 1995 to a consortium of Australia's Transfield Holdings and Japan's Obayashi Corporation, named Transurban Consortium. Transurban was formed in March 1996 to operate CityLink when completed. The total value of the project was estimated in 1996 at about $1.8 billion, and the concession to operate the road was initially due to expire in 2034. This concession has since been extended, and is now due to expire in 2045.

CityLink was built by the Transfield Obayashi joint venture under contract to Transurban between 1996 and 2000. The design and construction of the Western Link was subcontracted to Baulderstone Hornibrook, and the supply of the electronic tolling system was subcontracted to Translink Systems, a company jointly owned by Transfield Holdings and Transroute of France. The ongoing operation and maintenance of City Link was subcontracted by Transurban to Translink Operations, also jointly owned by Transfield and Transroute, which would manager the performance of CityLink assets. In May 1999, the operations were reorganised, with Transurban taking over the customer service operations from Translink Operations, who would retain responsibility for management of the tolling system, roadside assistance and maintenance.

The CityLink project was eight times larger than any other road project in Melbourne of that time. Toll plazas for manual tolling were deemed impractical, and delays associated with plaza operations would have decreased the advantages of using the new road. The decision to use only electronic toll collection was made in 1992; at a time when there was little practical experience of such systems. The first of the sections opened to traffic in 15 August 1999, with tolling commencing on 3 January 2000 before final completion occurred on 28 December 2000 with tolling commencing the same year.

When CityLink opened in 1999, the Southern Link was signed as M1 and the Western Link was signed as Metropolitan Route 43. Metropolitan Route 43 previously terminated at the Tullamarine Freeway/Calder Freeway interchange but it was extended along CityLink to end in Port Melbourne. Whilst National Route 79 officially remained part of the Western Link from the opening until 2013 (as the previous Tullamarine Freeway carried this designation from Calder Freeway to Flemington Road), CityLink signage did not show any National Route 79 signage and was exclusively signed as Metropolitan Route 43. With Victoria's conversion to the newer alphanumeric system in the late 1990s, Metropolitan Route 43 slowly began transition to M2 and was finally replaced with M2 in 2018. Despite this, a number of Metropolitan Route 43 shields remain visible to this day.

The passing of the Road Management Act 2004 granted the responsibility of overall management and development of Victoria's major arterial roads to VicRoads. CityLink is a privately-owned and operated tollway, but in June 2004, VicRoads became responsible for managing the CityLink concession contract and the state's assets (such as physical infrastructure including roads, bridges, tunnels and the tolling system operated by CityLink, due to be transferred to the state at the end of the concession period) under that contract, in an effort to improve the integration of CityLink with the rest of the road network. Later in 2004, it re-declared the Tullamarine Freeway to terminate at Mount Alexander Road (sign-posted as Bulla Road) in Strathmore, south of Essendon Airport: CityLink's Western Link officially begins east of this interchange in Strathmore, and ends with its interchange with West Gate Freeway in Port Melbourne. At the same time, VicRoads also re-declared the West Gate Freeway to terminate at Princes Highway East (today Kings Way) in Southbank, and the Monash Freeway to commence in Kooyong: CityLink's Southern Link officially runs between these two points at Southbank and Kooyong.

Existing roads
Previously, the city centre was served by three separate freeways:
 * The South Eastern Freeway (today the Monash Freeway), which had begun approximately 2 km south-east of the city, and connects Melbourne to the outlying rural Gippsland area;
 * The Tullamarine Freeway, which had begun approximately 5 km north-west of the city, and links Melbourne to Melbourne Airport, and also joins the Calder Freeway, which links Melbourne to Bendigo;
 * The West Gate Freeway which began in Southbank in the city's south, crossed the Yarra River over the West Gate Bridge and joined to both the Princes Freeway (linking to Geelong) and the Western Ring Road in Laverton North.

CityLink saw the linking of all three of these freeways: extending both the South Eastern and Tullamarine Freeways to join the West Gate Freeway. This also subsumed an existing portion of both the South Eastern and Tullamarine Freeways into the new project: while these portions were widened and upgraded, as part of the CityLink project they were also tolled, attracting criticism from road users.

Western Link
The elevated Western Link extended the existing Tullamarine Freeway, lengthening it to terminate it five kilometres further south at the West Gate Freeway in Port Melbourne, for a total distance of 12.9 km. It included a new major bridge (the Bolte Bridge, named after former Victorian Premier Sir Henry Bolte) over the Yarra River in the Docklands district; a long elevated section over Dudley Flats and Moonee Ponds Creek and a tube-like sound barrier in Flemington where the road passes close to a number of community housing towers. A short distance to the north of the sound tube, a massive sculptural work was placed, called the Melbourne International Gateway, consisting of a giant yellow beam hanging diagonally across the road (nicknamed the "Cheesestick") and a row of smaller red beams alongside the road (the "Zipper", or "rack of lamb"). The existing portion of Tullamarine Freeway between Flemington Road and Bulla Road was subsumed into the Western Link, and was also widened, with a transit lane being added in each direction between Flemington Road and Pascoe Vale Road.

This section of Freeway was originally designated in the 1969 Melbourne Transportation Plan as part of the F14 Freeway Corridor.

Southern Link
The underground Southern Link directly connects the ends of the West Gate and Monash Freeways into one continuous through-way, for a total distance of 8.0 km. This link comprises the Burnley and Domain Tunnels which pass under the Royal Botanic Gardens and the Yarra River, each tunnel channelling traffic in different directions. The existing portion of South Eastern Freeway between Toorak Road and Batman Avenue was subsumed into the Southern Link, and was also widened.

This section of Freeway was shown in the 1969 Melbourne Transportation Plan as part of the F9 Freeway corridor as a surface-level road.

Batman Avenue
The Exhibition Street Extension – not a part of the initial project, as it had been promoted as a bypass that would keep cars out of the CBD – consisted of a new four-lane, divided road extending south from the intersection of Flinders and Exhibition Streets in the CBD and spanning the Jolimont rail yards to connect with Batman Avenue near Melbourne Park Tennis Centre. Construction was managed by VicRoads on behalf of the Department of Infrastructure and began in November 1997, for a total distance of 1.9 km completed to coincide with the opening of CityLink. The alignment of Batman Avenue, previously following the northern bank of the Yarra River north of Swan Street to terminate at Swanston Street just north of Princes Bridge, was re-routed to follow this new road; the route 70 tram, previously using this alignment, was also re-routed to run on a dedicated median behind the Melbourne Park complex and re-join the new road before it crossed the rail lines, commencing along this new route from 7 June 1999. It was officially opened as Batman Avenue on 1 November 1999; the former alignment is now a pedestrianised walking track. Costing $30 million, the access road was built as part of CityLink and therefore attracts tolls.

Project overview
The freeway had extensive upgrades between 2015 and 2018, including the addition of lanes as part of the CityLink Tulla Widening Project.

Original proposal (2014)
The original project was announced in April 2014 by then-Premier Denis Napthine as an unsolicited proposal by Transurban, with Transurban providing the bulk of the funds for the upgrade. The original design would have involved the widening of the entire Western Link of Citylink up to Bulla Road (Stage 1) and the Tullamarine Freeway from Bulla Road to Melrose Drive (Stage 2). In addition, Transurban's tolling concession was extended by a year, to 2035. Work on the original upgrade was expected to commence construction early–mid 2015, and was expected for completion by early–mid 2018. The original project was designed to complement the former East West Link project which was cancelled after Daniel Andrews won government at the State election in November 2014. This led to the original project being postponed and modified.

Final proposal (2015–2018)
In August 2015 a new proposal to widen the Citylink and Tullamarine Freeways was put into action by the recently elected Premier Daniel Andrews. The project consists of two stages which would increase the road's daily capacity as well as shorten trips between Melbourne Airport and the CBD during morning peak and afternoon peak times. The following upgrades started in October 2015 (Stage 1) and May 2016 (Stage 2). The entire project is completed by late 2018. The upgrade involves the construction of a new lane in each direction from Melbourne Airport to Power Street, upgrades to the Bell Street, Flemington Road, English Street and Mickleham Road intersections, and the creation of a dedicated lane between the Calder and Tullamarine Freeways to Bell Street, to reduce weaving. Speed limits will be lowered on parts of the freeway during construction work, and after construction, as a result of lane narrowing. The project will also install an electronic freeway management system, involving CCTV cameras, a variable speed limit, and electronic message signs.

Controversy has arisen due to the proximity of Strathmore Secondary College to the new ramp at Bell Street. The removal of a tree as part of the Flemington Road intersection upgrade also resulted in public protest.

Stage 1 (Bulla Road to Power Street)

 * Lane use management signs to manage which lanes are open
 * Variable speed limit signs above all lanes
 * Ramp signalling – stop and go traffic lights to improve traffic flow and reduce congestion as traffic enters the freeway from on-ramps
 * CCTV cameras – to monitor for incidents, help response times and minimise disruptions
 * Travel time information signs so people can plan their journey
 * Electronic message signs – to notify road users of planned changes or disruptions
 * Automatic incident detection system – to alert road managers of incidents in real time
 * Two dedicated lanes inbound to Bell Street from the Tullamarine Freeway and Calder Freeway
 * New Bell Street to Pascoe Vale Road
 * Improvements to Flemington Road/ Mount Alexander Road Freeway Interchange
 * Additional outbound lane between Moreland and Ormond Road
 * Ramp widening between Bolte Bridge and West Gate Freeway
 * One additional inbound lane between Montague Street and Ingles Street
 * One additional inbound lane between Montague Street and Power Street

Stage 2 (Melbourne Airport to Bulla Road)

 * A new structure with dedicated lanes from the Tullamarine Freeway and Mickleham Road to the M80 Ring Road inbound to ease congestion and reduce traffic weaving
 * An extra lane entering the Tullamarine Freeway city bound from Mickleham Road
 * Reconstruction and widening of the English Street overpass and all ramps to increase capacity into and out of Essendon Fields
 * Ramp signals on the city bound entry from Kings Road in Taylors Lakes to the Tulla Calder interchange to regulate the flow of traffic getting onto the Tullamarine Freeway from the Calder Freeway

Extra lanes
Part of the upgrade is adding more lanes between Melbourne Airport and the West Gate Freeway. Between the Citylink (Western Link) and the West Gate Freeway, one additional lane in each direction will be added consuming the current emergency lanes as well as lower the current speed limit from 100 km/h down to 80 km/h.

Tolling system
There are no toll booths along the entire length of the system, so traffic flow is not impeded.

CityLink uses a DSRC toll system called e-TAG, where an electronic transponder is mounted on the inside of vehicles' windscreens. Gantries constructed over each carriageway record registration plates and detect the e-TAGs, and deduct toll amounts automatically from the account linked electronically to each tag. Where a tag is not detected, the vehicle's registration is recorded using an automatic number plate recognition system and checked against a database. For infrequent use of the system one can buy a Daypass – by phone, online, at any Australia Post outlet or at participating service stations. A Daypass can be bought in advance or afterwards (until midnight three days later). If payment has not been made, the vehicle's registered owner will be sent a late toll invoice in the mail, and if the late toll invoice is then not paid a fine will be issued by Civic Compliance Victoria.

In 2018 CityLink tolling accounts were rebranded as Linkt, as part of parent company Transurban combining their existing retail brands.

The concession period held by Transurban is due to end in 2045, after which the ownership of the road will be transferred to the state. It was originally due to end in January 2035, but was extended as part of a deal with Transurban to build the West Gate Tunnel project.

Toll points
Multiple toll points are located along the CityLink, with each toll point charging a fixed fee. The CityLink toll points also include the toll point at the Exhibition Street extension (Batman Avenue). The total toll incurred per trip is the smaller of the trip cap or the total price of toll points passed through.

The entry and exit ramps of CityLink (excluding West Gate Freeway) have been constructed in a way that travelling on any section of CityLink will always pass through at least one toll point. The only exception is eastbound travel between Punt Road and Church Street, which does not pass through a toll point and hence does not incur any tolls.

Batman Avenue
Batman Avenue is entirely contained within the City of Melbourne local government area.

Controversies
As part of the development of CityLink, portions of existing roads were subsumed into the CityLink project: while they too were upgraded and expanded, tolling points were also added. Toll charges now apply to the former Monash Freeway between Toorak Road and Punt Road, and the former Tullamarine Freeway south of Bulla Road. Previously public roads, they did not incur tolls to use before.

Some nearby roads were altered to restrict rat runs to stop people using neighbourhood back streets as short cuts to avoid the toll. Some people have viewed this as local councils 'forcing' people to use CityLink.

CityLink account holders can, if they make multiple trips in a day, pay more to use the road than a casual user. A 24-hour Pass, for example, is charged at a flat rate, but an account holder pays per trip. Account holders who make multiple trips in a single day may pay more than a pass customer would. However, CityLink recognises this and account customers can remove their e-TAG device and buy a pass for the day: just like casual customers. However, there is a limit to the number of passes that can be bought each 12 months. This limit applies to account holders and casual users.

The contract between the government and CityLink's owner Transurban has protections for both parties. One of these is the ability for Transurban to make a claim against the state government if the state government does something that reduces the number of cars that could use CityLink. In 2001 Transurban commenced legal proceedings against the State of Victoria over the construction of Wurundjeri Way through the Melbourne Docklands. It was alleged that this 'free' road was competing with CityLink and causing it to earn less revenue. This can potentially also be applied if the capacity of other roads or rail routes parallel to CityLink are expanded, however the contract specifically excludes compensation if the metropolitan rail network is extended to Melbourne Airport.

CityLink received negative media coverage when it was wrongly claimed that CityLink account holders' credit card details were stored on Transurban's public webserver and that someone had broken into the system and stolen tens of thousands of customers details. Customer details were stolen, not by an intruder via the web, but by a former employee who had misused access to the secure IT systems.

The two CityLink tunnels have regularly featured as discussion points on talkback radio, firstly for air quality. In the early days of operation, the air quality in the tunnels appeared smoggy. CityLink worked a way around the problem by adjusting the venting system which improved quality and dispersed exhaust fumes more effectively. The second issue was regarding the use of massive quantities of fresh drinking water pumped into the system to stabilise the tunnel environs. After some time, CityLink sought and obtained approval from the State Government to build a water recycling plant which meant they could rely primarily on recycled, and not drinking, water.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: CityLink


text:
Talk:Exotic probability

Can you give cites for the topics in this article, please? Many of the terms used in it cannot be found anywhere on the Web. -- The Anome 01:34, 8 Mar 2004 (UTC)

This article appears to be somewhat suspicious. Examples:
 * Lawrence M. Krauss is not listed as a Nobel laureate, although he is a real theoretical physicist who wrote a book on the "Physics of Star Trek".
 * The term "Lebesgue Dice" does not occur anywhere in the sense intended in Google's index.
 * Nor does "Manning-McArdle Conjecture".

-- The Anome 08:16, 8 Mar 2004 (UTC)

 * It sounds weird, but as weird as many of Feynmann's inventions. I'd rather keep the article but it is really badly written... "is when...". If I have the time I may want to fix it, but do not trust me for it. In any case, things as negative probabilities, etc... have been discussed in academic circles (although I do not know about specific references, but I am not an expert). I took the notice away but put a stub one. Pfortuny 08:29, 8 Mar 2004 (UTC)

Citation for the Gowers paper, please. I'm inclined to treat this as a leg-pull until I'm convinced about that.

Charles Matthews 08:47, 8 Mar 2004 (UTC)

OK, I'm convinced this is a student prank. I say delete.

Charles Matthews 16:20, 9 Mar 2004 (UTC)

These look like real references to me:

 * http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995NYASA.755..904Y
 * http://fnalpubs.fnal.gov/library/colloq/colloqyoussef.html

Also my quantum physics is a little sketchy, but one of the references cited is "How much time does a tunneling particle spend in the border region?". I would not, on my own knowledge, rule out the idea that the answer to that question may be negative. Of course, I may be wrong. DJ Clayworth 16:39, 9 Mar 2004 (UTC) DJ Clayworth 16:36, 9 Mar 2004 (UTC)

I have trimmed this down to only material that can be corroborated from the Web. I agree, the original looked like a leg-pull with a smidgen of true material to add confusion. Unless someone can give a cite. -- Anon.

 * I think the article as it is is a good starting point. Someone knowing about Feynman's ideas might add something more (ideas of which I only have a scent). Pfortuny 20:31, 9 Mar 2004 (UTC)

 * Delete. Feynman was a Bayesian, as you would expect for a physicist. My recollection from Feynman, is his sentence "Probability is best defined by betting". The red flag is the minor tag from the originator of this article, clearly a student prank. dmn's bogus Weisstein URL is a clear indication of a prank. Ancheta Wis 07:24, 18 Mar 2004 (UTC)

I heard Youssef give a paper at a scientific conference in Santa Fe several years back examining complex probabilites and the theory was treated seriously though not all agreed with the suggestion. I suggest keeping it. Tony Vignaux 07:33, 2004 Mar 18 (UTC)

An older version of this article was re-added to the end of the article; this has already failed to meet the criteria for being included here, as it was prima facie dubious, searches for terms in it came up with nothing, and no cites were given to support the assertions given. Deleted. -- Karada 10:54, 28 May 2004 (UTC)

Just for the record, it's an anonymous ip that changed it back to the nonsense version, and I added the non-nonsense version to the top while going through the ip's questionable edits. Hadn't seen that the ip was actually just reverting to a fake older version (calling it a spelling mistake), or I'd just have reverted completely. Κσυπ Cyp    11:00, 28 May 2004 (UTC)

title: Talk:Exotic probability


text:
Talk:Common Broom

 * The following discussion is an archived debate of the . Please do not modify it. Subsequent comments should be made in a new section on the talk page. No further edits should be made to this section.

move to scientific name - MPF 11:59, 25 May 2006 (UTC)

The spelling "scotch broom", sometimes seen, is to be avoided, as it is offensive to the people of Scotland. (The preceding unsigned comment left by MPF (talk | contribs) on 18:35, 7 March 2004)

 * Be that as it may, it is by this name that it is commonly known on the west coast of the United States, without any discernable intent to offend the Scottish. (The preceding unsigned comment left by 65.182.242.36 (talk | contribs) on 21:42, 17 May 2004)

 * I concur with 65.182.242.36. Common naming conventions dictate that the page be located at the name of the most common name.  A google search reveals:
 * "Common Broom" Cytisus: 574 hits (included the "Cytisus" search term to avoid hits for the household cleaning brooms...)
 * "European Broom" Cytisus: 129 hits
 * "Scots Broom" Cytisus: 323 hits
 * "Irish Broom" Cytisus: 599 hits
 * "English Broom" Cytisus: 716 hits
 * "Scotch Broom" Cytisus: 52,700 hits
 * I would suggest this article be moved to Scotch Broom. If anyone else is watching this article, I would appreciate support or oppose motions in regards to the move.  If no motions appear in either favor, I will simply move the article in a week.  -Rkitko 06:27, 13 May 2006 (UTC)

 * Since no one has replied, I have moved the article to its new home per common naming conventions. I will continue to keep this page on my watchlist so if anyone wishes to add comments later to this discussion, I will reply if new information can bring to light why this article shouldn't be located at this name.  I have also fixed all of the redirects and double redirects to point directly to this article.  --Rkitko 21:30, 18 May 2006 (UTC)

 * Absolutely disagree. This is US imperialism at its worst. - MPF 22:14, 18 May 2006 (UTC)

 * I won't move it back immediately because I don't want to get into a revert war, but please explain your rationale more carefully using Wikipedia policy. Instead of accusing me of unfairly representing US interests, please review WP:NC(CN).  I see no mention of imperialism.  I'm also unfamiliar with the policy that states offensive article titles (to some) are to be avoided (personally, I think words have no meaning.  Intent to offend behind a word is what has greater meaning.  And of course no offense is meant here.  I digress).  From what I've read, the common name of this species is Scotch Broom.  If you can provide a source that notes that simply "Broom" is the most common name of all, then I will have to re-examine my position.  But for now, you can't simply change article names based on an unsourced opinion that it offends someone.  Have you gone and moved Scotch whisky yet?  Instead of reverting immediately, I would have liked the opportunity to respond in this manner before such a decision was made, just as I allowed ample time for anyone watching this page to respond.  Thanks.  --Rkitko 22:56, 18 May 2006 (UTC)

 * Because the species is a British native, and that name is never used for it in Britain, only in the US, where the species is not native. Wikipedia naming rules state that the name in use varies between areas, the name used should be that used in the area to which the topic is relevant; i.e., the British name. US re-naming of our plants (and then telling us to use the US-version) is what I mean by imperialism. The US has no authority to decide on the names of plants which are not theirs.
 * "If you can provide a source that notes that simply "Broom" is the most common name of all" - look at any UK flora, such as Stace, or Clapham, Tutin & Warburg, or Blamey & Grey-Wilson, or McClintock. Or, online,, , , , etc, etc. - MPF 23:17, 18 May 2006 (UTC)

 * Thanks for the links. I hadn't detected any of these in my google search.  Very difficult to search for something like this that has such a common name with other meanings.
 * "the name used should be that used in the area to which the topic is relevant"... How does one decide where the topic is more relevant? Does it have any great significance in its native range?  Is it more "relevant" in its invasive range?  Where is it more economically relevant?  I think these things should definitely be addressed in the article itself.  And if you're suggesting that original names of things should be the article titles ("The US has no authority to decide on the names of plants which are not theirs.") then why not revert all articles dealing with locations or things that have native names (we call it Mount Everest...  the local populations don't)?  Please explain why you think the native range of this plant is more relevant than its invasive range.  How else can we determine what the most common name is?  Is there some other means by which we can examine this debate? --Rkitko 00:19, 19 May 2006 (UTC)

 * MPF, I know you oppose the move to Scotch Broom and though I disagree with your reasoning, I'd come the conclusion that it wouldn't be the best name for the article. The requested move noted above and discussed below is not specifically to move the article to Scotch Broom--that's why I used , which encourages voting on other options.  And from what you wrote below, I would actually support moving the article to Cytisus scoparius.  I justify that move from the following (I know it's specifically for fauna, but no real discussion has occurred for the Plants Wikiproject): Naming conventions (fauna).  "If there is no common name, or if the only common name would be taken by a higher-ranked group, or if the only common name is needed for another article or a disambiguation page, use the scientific name."  Because the true common name for this plant, as you suggest, is really just "Broom" it doesn't belong here at Common Broom but really at its scientific name and also listed on the Broom (disambiguation) (the genus is there, but this species should also be listed).  Your thoughts?  -Rkitko 02:56, 24 May 2006 (UTC)
 * Cytisus scoparius works for me, with redirects from all the common names. BTW, Scotch Broom is the most common name in New Zealand, nobody means any offence by it. Onco_p53 03:35, 24 May 2006 (UTC)

I'll be happy with scientific name titling too, and can move it (on the assumption that this satisfies everyone; I'll wait till tomorrow in case anyone else wants to comment first). - MPF 18:30, 24 May 2006 (UTC)

Requested move
Google search reveals that "Common Broom" is not the most common name for this plant. Because of difficulties determining how common "Broom" is for the plants name in a google search, I proposed a move to "Scotch Broom", a term that is well-known. However, "Scotch Broom" is used mostly in its invasive range, while in its native range it's known as simply "Broom," leading to a conflict. Either way, "Common Broom" is not the most common name, which is why options and opinions are encouraged for this requested move. Rkitko 05:40, 21 May 2006 (UTC)

Survey

 * Add *Support or *Oppose followed by an optional one-sentence explanation, then sign your opinion with  ~

 * Very Strong Oppose - the suggested name is considered offensive within the species' native range, and is not used there at all. The Wiki page naming guidelines, and common courtesy, state that preference should be given to names used in the area most relevant to the subject, which is its native area. - MPF 01:57, 24 May 2006 (UTC)

Discussion

 * Add any additional comments

 * Disagree with the contention above as to the commonest name. A google search for Cytisus scoparius gives 257,000 hits, while a search for Cytisus scoparius -scotch gives 202,000 hits, i.e., 80% of references to the species do not use the term 'scotch'. - MPF 01:57, 24 May 2006 (UTC)
 * Move to Cytisus scoparius. Redirect Scotch broom and Common broom to it.--Curtis Clark 04:05, 24 May 2006 (UTC)

 * The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made in a new section on this talk page. No further edits should be made to this section.

title: Talk:Common Broom


text:
Mac OS 8

Mac OS 8 is the eighth major release of the classic Mac OS operating system for Macintosh computers, released by Apple Computer on July 26, 1997. It includes the largest overhaul of the classic Mac OS experience since the release of System 7, approximately six years before. It places a greater emphasis on color than prior versions. Released over a series of updates, Mac OS 8 represents an incremental integration of many of the technologies which had been developed from 1988 to 1996 for Apple's overly ambitious OS named Copland. Mac OS 8 helped modernize the Mac OS while Apple developed its next-generation operating system, Mac OS X (renamed in 2012 to OS X and then in 2016 to macOS).

Mac OS 8 is one of Apple's most commercially successful software releases, selling over 1.2 million copies in the first two weeks. As it came at a difficult time in Apple's history, many pirate groups refused to traffic in the new OS, encouraging people to buy it instead.

Mac OS 8.0 introduces the most visible changes in the lineup, including the Platinum interface and a native PowerPC multithreaded Finder. Mac OS 8.1 introduces a new, more efficient file system named HFS Plus. Mac OS 8.5 is the first version of the Mac OS to require a PowerPC processor. It features PowerPC native versions of QuickDraw, AppleScript, and the Sherlock search utility. Its successor, Mac OS 9, was released on October 23, 1999.

Copland
Starting in 1988, Apple's next-generation operating system, which it originally envisioned to be "System 8" was codenamed Copland. It was announced in March 1994 alongside the introduction of the first PowerPC Macs. Apple intended Copland as a fully modern system, including native PowerPC code, intelligent agents, a microkernel, a customizable interface named Appearance Manager, a hardware abstraction layer, and a relational database integrated into the Finder. Copland was to be followed by Gershwin, which promised memory protection spaces and full preemptive multitasking. The system was intended to be a full rewrite of the Mac OS, and Apple hoped to beat Microsoft Windows 95 to market with a development cycle of only one year.

The Copland development was hampered by many missed deadlines. The release date was first pushed back to the end of 1995, then to mid-1996, late 1996, and finally to the end of 1997. With a dedicated team of 500 software engineers and an annual budget of $250 million, Apple executives began to grow impatient with the project continually falling behind schedule. In August 1996, Apple chief technology officer Ellen Hancock froze development of Copland and Apple began a search for an operating system developed outside the company. This ultimately led to Apple buying NeXT and developing Rhapsody which would eventually evolve into Mac OS X in 2001 (now named macOS).

At the Worldwide Developers Conference in January 1997, Apple chief executive officer (CEO) Gil Amelio announced that, rather than release Copland as one monolithic release, Copland features would be phased into the Mac OS following a six-month release cycle. These updates began with Mac OS 7.6, released during WWDC. Mac OS 8.0, released six months later, continued to integrate Copland technologies into the Mac OS.

Mac OS 8.0
Developed with the codename "Tempo", Mac OS 8.0 was announced on July 22, 1997, and released on July 26. The early beta releases of the product which were circulated to developers and Apple internal audiences, were branded as Mac OS 7.7, superseding the then-current release, Mac OS 7.6. The software was renamed Mac OS 8 before final release.

Major changes in this version included the Platinum theme, a Finder which was PowerPC-native and multithreaded, and greater customization of the user interface.

Other features introduced in Mac OS 8.0 include the following:

 * Customization of system fonts and increased use of the user-set accent color.
 * Pop-up context menus, accessed via ctrl-click with a one-button mouse.
 * Pop-up (or tabbed) windows in the Finder.
 * Spring-loaded folders.
 * Live scrolling.
 * WindowShade widget in window titlebars.
 * Multithreaded Finder — file copy operations run in a separate thread and don't block the Finder UI.
 * Redesigned color picker.
 * Desktop Pictures control panel, allowing photographs to be set as the desktop background; not only tiled patterns.
 * Simple Finder, an option which reduces Finder menus to basic operations, to avoid overwhelming new users.
 * Relocation of the 'Help' menu from an icon at the right end of the menu bar to a standard textual menu positioned after the application's menus.
 * A faster Apple Guide, featuring HTML help pages.
 * Native support of Apple Filing Protocol over IP.
 * Performance improvements to virtual memory, AppleScript execution and system startup times.
 * Faster desktop rebuilding.

Mac OS 8.1
Released on January 19, 1998, Mac OS 8.1 was the last version of the Mac OS to run on Macs with Motorola 68000 series processors. It addressed performance and reliability improvements. It introduced a new file system named HFS+, also named Mac OS Extended, which supported large file sizes and made more efficient use of larger hard drives via using a smaller block size. To upgrade, users must reformat the hard drive, which deletes the entire contents of the drive. Some third-party utilities later appeared that preserved the user's data while upgrading to HFS+. The 68040 systems do not support booting from HFS+ disks; the boot drive must be HFS.

Mac OS 8.1 was the first system to have a Universal Disk Format (UDF) driver, allowing for DVD support on the Mac for the first time. It also shipped with the new Java runtime (JDK 1.1.3).

Mac OS 8.1 also included an enhanced version of PC Exchange, allowing Macintosh users to see the long file names (up to 255 characters) on files that were created on PCs running Microsoft Windows, and supporting FAT32.

Mac OS 8.1 is the earliest version of the Mac OS that can run Carbon applications. Carbon support requires a PowerPC processor and installation of the CarbonLib software from Apple's website; it is not a standard component of Mac OS 8.1. Applications needing later versions of CarbonLib will not run on Mac OS 8.1. More recent versions of CarbonLib require Mac OS 8.6.

As part of Apple's agreement with Microsoft, 8.1 included Internet Explorer 3 initially, but soon switched to Internet Explorer 4 as its default browser.

Mac OS 8.1 was free for Mac OS 8 owners and was available in February 1998 via the apple.com website.

Mac OS 8.5
Released October 17, 1998, Mac OS 8.5 was the first version of the Mac OS to run solely on Macs equipped with a PowerPC processor. If Mac OS 8.5 is installed on a 68k system, the Sad Mac error screen will appear. As such, it replaced some, but not all, of the 680x0 code with PowerPC code, improving system performance by relying less on 680x0 emulation.

It introduced the Sherlock search utility. This allowed users to search the contents of documents on hard drives (if the user had let it index the drive), or extend a search to the Internet. Sherlock plug-ins started appearing at this time; these allowed users to search the contents of other websites.

Mac OS 8.5 includes several performance improvements. Copying files over a network was faster than prior versions and Apple advertised it as being "faster than Windows NT". AppleScript was also rewritten to use only PowerPC code, which improved AppleScript execution speed significantly.

Font Smoothing, system-wide antialiasing for type was also introduced. The HTML format for online help, first adopted by the Finder's Info Center in Mac OS 8, was now used throughout. This made it easier for software companies to write online help systems. The PPP control panel was removed and replaced with Remote Access, which provides the same functionality but also allows connections to AppleTalk Remote Access (ARA) servers.

The installation process was simplified considerably in Mac OS 8.5. In earlier versions the installer worked in segments and often required a user to click to continue in between stages of the installation. This was a holdover from the days when the OS was distributed on multiple floppy disks, disk swapping promoting a natural segmentation model. The Mac OS 8.5 installer generally required very little user interaction once it was started. Customisation options were also much more detailed yet simpler to manage.

From Mac OS 8.5 onward, MacLinkPlus document translation software is no longer bundled as part of the Mac OS.

Mac OS 8.5 was the first version of the Mac OS to support themes, or skins, which could change the default Apple Platinum look of the Mac OS to "Gizmo" or "HiTech" themes. This radical changing of the computer's appearance was removed at the last minute, and appeared only in beta versions, though users could still make (and share) their own themes and use them with the OS. The Appearance control panel was also updated to support proportional scroll bars, and added the option for both scroll arrows to be placed at the bottom of a scroll bar.

Along with themes support, 8.5 was the first version to support 32-bit icons. Icons now had 24-bit color (16.7 million colors) and an 8-bit alpha channel, allowing for transparency-translucency effects.

The application palette made its debut with 8.5 – the application menu at the right side of the menu bar could be resized to show the active application's name, or 'torn off' into a palette of buttons. This palette could be customized in many ways, by removing the window frame and changing the size and layout of the buttons. Apple provided no user interface to set these options, instead making them available via AppleScript and Apple Events and relying on third parties to provide a user interface for the task. By setting it to display horizontally and turning off the window border, the palette's look and function could be configured to resemble the Windows 95 task bar.

Mac OS 8.5.1
Mac OS 8.5.1, released December 7, 1998, was a minor update to Mac OS 8.5 that fixes several bugs that caused crashes and data corruption.

Mac OS 8.6
Mac OS 8.6 was released on May 10, 1999 as a free update for Mac users running 8.5 and 8.5.1. It added support to the Mac OS nanokernel to handle preemptive tasks via the Multiprocessing Services 2.x and later developer API. Mac OS 8.6 improved PowerBook battery life, added Sherlock 2.1, and is faster and much more stable than either version of 8.5.x. It is the first version of Mac OS to display the version number as part of the startup screen. However, there is no process separation; the system still uses cooperative multitasking between processes, and even a process that is Multiprocessing Services-aware still has a portion that runs in the "blue task", which also runs all programs that are unaware of it, and was the only task that can run 68k code.

Reception
While CNET's initial review of Mac OS 8 was more circumspect, its editorial staff named it one of the best products of 1997 in their year-end roundup.

title: Mac OS 8