h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

It's incorrect to say that "gyratory system" is just the name for a roundabout that has got too big for its boots. In fact it's the original term which was soon displaced when they became common.

I'm not sure if the term "gyratory circus" was ever really used. There are a number of junctions in London known as circuses after the circular range of buildings around them. This was a particularly 18th century fashion, so of course the most famously beautiful one is in Bath.



The OED says of "gyratory":

Applied to a system of directing road traffic round a roundabout or through a system of one-way streets to avoid the need for one line of traffic to intersect another.

1909 Westm. Gaz. 7 Aug. 4/2 The gyratory principle, by which vehicles are directed into circular lines ingeniously devised to avoid intersection. 1926 Rep. Comm. Police Metropolis, 1925 16 in Parl. Papers (Cmd. 2660) XV. 239 Gyratory systems for the circulation of traffic, after years of discussion, reached the point of practical demonstration this year. 1928 Observer 5 Feb. 13/7 Now that every week dedicates a new bunch of streets to the Gyratory System. 1966 Guardian 8 Sept. 5/4 A new gyratory road system to ease traffic congestion..is to be built..at Stretford.



And of "roundabout":

A junction at which traffic moves one way round a central island. Cf. RONDPOINT b, ROTARY n. 3.

1927 Glasgow Herald 3 Jan. 7/2 There is only one draw~back to the roundabout, and that is the inconvenience caused to pedestrians. 1937 Times 13 Apr. (British Motor No.) p. viii/1 Roundabouts..have the advantage of keeping vehicles on the move. 1947 Daily Mail 22 May 3/4 Removal of the Mansion House to make room for a big round-about. 1955 Times 2 Aug. 9/7 Makeshift tactics are particularly evident in the proposed treatment at Hyde Park Corner which includes an extremely complicated roundabout. 1967 Listener 28 Sept. 398/1 People make only occasional use of their speedometer..on such critical occasions as the approach to roundabouts. 1977 Belfast Tel. 14 Feb. 5/9, 12 shots were fired at an armoured police vehicle near the roundabout at Narrow~water Castle.



And of "circus":

A circular range of houses. Also, a traffic roundabout. Often in proper names as Oxford Circus, Regent Circus.

1714 POPE Rape Lock IV. 117 Sooner shall Grass in Hide-Park Circus grow. 1766 ANSTEY Bath Guide II. ix. 57 To breathe a purer Air In the Circus or the Square. 1771 SMOLLETT Humph. Cl. 23 Apr., The same artist who planned the Circus has likewise projected a crescent [at Bath]. Ibid. The Circus is a pretty bauble..and looks like Vespasian's amphitheatre turned outside in. 1794 Looker-on No. 89 The squares and circuses are no longer the only scenes of dignified dissipation. 1898 Tit-Bits 15 Jan. 300/3 Bridges, of light and tasty design, across all the main thoroughfares, and at the various ‘circuses’ and cross roads.

I'm a little confused. The definitions you gave seem to support the idea that there *is* a difference between a roundabout and a gyratory.

Those definitions say that a roundabout is a junction, while a gyratory is a particular kind of one way system.

Of course a roundabout could be viewed as a very small one way system, so you could argue that all roundabouts are gyratories. But not all gyratories are really roundabouts according to the definitions you produced. (Specifically, a gyratory consisting of more than one junction is, by definition, not a roundabout.)

But in practice, isn't the common usage pretty much as I suggested? I'm only actually aware of two road systems commonly referred to as gyratories - one is the subject of this article, and the other is in Reading. And both of them are distinctly on the large side. In particular, they both have multiple junctions.

So the common usage of the word seems to be to describe overgrown roundabouts (and more specifically, multi-junction ones) in practice.

Can you point to any counterexamples in real use? I'm just going on the gyratories I know - I've not done any exhaustive research on gryatories across the nation.

There is a gyratory system at Park Gate near Southampton that consists of a pair of roundabouts connected by a pair of one way carriage ways.

I have to correct my previous entry because, while I have heard it called the Park Gate gyratory system, it is not recorded as a gyratory system on Hampshire's register of adopted roads. It is recorded as the following separate components... Botley Road roundabout, the Bridge Road dual carriageway and the Brook Lane roundabout.
However, I find there is a gyratory system just east of Park Gate on the A27 at Titchfield and this is a large roundabout with traffic lights and many junctions.