Talk:Roundabout

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Hamburger Roundabout[edit]

There is an example here (Perth, Western Australia. Morley Drive (east-west), Alexander Drive (north-south), The Strand (NW-SE). The existing roundabout was bisected some time in the 1980's. --michael 07:03, 6 May 2006 (UTC)


There is an example here in Fairfax, VA, US, at the intersection of US 29/VA 237 Lee Hwy, US 50 Fairfax Blvd, US 29/50 Fairfax Blvd, and Old Lee Hwy. US 50 goes through the circle, US 29 goes partway through the circle, and VA 237 the goes around it. séain (talk) 02:47, 21 August 2008 (UTC)

capacity vs conventional intersections[edit]

"Roundabouts are not suitable for junctions where the exits suffer from traffic congestion. Congestion on one exit commonly blocks a roundabout and spreads to all entering directions. " All intersections suffer if spillback from an adjacent intersection extends through them. Why make a special point about it for roundabouts? --Triskele Jim 16:36, 29 October 2007 (UTC)

OK. Paragraph removed to here -- together with adjunct about Kwai Tsing Interchange since that is uncited.--Farry 19:55, 12 November 2007 (UTC)

"Roundabouts are not suitable for junctions where the exits suffer from traffic congestion. Congestion on one exit commonly blocks a roundabout and spreads to all entering directions. The roundabout of Kwai Tsing Interchange in Hong Kong was replaced by a large box junction with traffic lights after recurring area traffic congestion when numerous container trucks journeyed to Kwai Chung Container Port after a typhoon."

I think the point is that if a signalized intersection has more volume than capacity, then traffic backs up and you start queing, LOS F and more... ...but the intersection still 'works.' When a roundabout has more volume than capacity at the exits, and the queues back up, the roundabout is typically 'paralyzed' with no movement anywhere; maybe only between adjacent exits with multi lane roundabouts.Wvfd14 (talk) 12:28, 20 May 2008 (UTC)
A yield-on-entry roundabout will continue to flow when over capacity, perhaps better than a signal, since ther is no lost time for phase changes. Roundabouts almost always have more capacity at the exits than the entrances. Problems occur when the next downstream intersection backs up through the roundabout, but this hurts all types of intersections.
A separate problem is traffic circles where circulating traffic must yield to entering traffic. These will gridlock themselves.Triskele Jim (talk) 17:09, 20 May 2008 (UTC)
Does the fact that these two images show driving on the right reflect some bias? The intersection example is an oversimplification, because the left turners don't cross each other's path, but they certainly have to cross any straight-through traffic, which would have the right of way. The advantage of the roundabout is that straight-through traffic does not impede the left turner (in a driving on the right example). Roundabouts become congested when there is one dominant stream making a 270 degree turn, such as at rush hour. Traffic still moves freely on the roundabout, but only in the dominant stream, and drivers at the intermediate entrances find it hard to break in. This situation is easily cured by the signalized roundabout, which can force gaps in the dominant stream.24.108.87.94 (talk) 23:14, 27 December 2008 (UTC)

I have tagged the Capacity section for NPOV. The POV problem is the discussion of the "conventional" intersection. In many intersections of this design, the two vehicles trying to turn across traffic (left, in the case of these two illustrations) will cross behind each other. This means their paths cross twice, exactly as in the roundabout example. Generally, these turning vehicles turn in front of each other only when they enter the intersection from dedicated turn lanes that face each other, in a signalized intersection, and the there are dedicated turn arrow signals. This requires a wider intersection, a signalized intersection, a more complex signaling pattern, and longer delays for all vehicles using the intersection. --Una Smith (talk) 15:45, 25 June 2009 (UTC)

"Roundabouts and cyclists" section[edit]

The subheadings should be merged, because their subjects overlap and there are several repeating sentences. Admiral Norton (talk) 20:45, 24 February 2008 (UTC)

I disagree. Cyclists and pedestrians have quite different needs and characteristics. This is especially true at roundabouts. Pedestrians are often safer at roundabouts, but cyclists often run into problems, especially at multi-lane roundabouts. Perhaps these sections could be re-written, but I don't think they should be merged. —Preceding unsigned comment added by Triskele Jim (talkcontribs) 20:46, 25 February 2008 (UTC)

Turbo roundabouts[edit]

I've added a stub for turbo roundabouts, and an image showing one schematically. English is not my native language, so my contribution will probably need some editing. See also http://nl.wikipedia.org/wiki/Turborotonde. 82.95.131.38 (talk) 23:29, 11 April 2008 (UTC)

Wow... that looks almost intentionally evil. I'm confused as to how it's supposed to work effectively, except for people turning left (and then only a slight improvement). For one thing it appears to give you a different flexibility of travel direction depending on whether you're north/south or east/west - or is that just an artist error? 193.63.174.210 (talk) 19:56, 17 November 2008 (UTC)
I'm confused you are saying it's evil. I don't understand that. In the Netherlands we now have almost 80 turbo roundabouts and the number is still increasing. One-lane roundabouts do not have a high capacity. So that is why two-lane roundabouts are being build. Two-lane roundabouts have a higher capacity but also lower road safety compared to one-lane roundabouts due to the higher speed and the risk of wrong lane changing. A turbo roundabout has a higher capacity than an one-lane roundabout but it has the same traffic safety. If you have any questions feel free to ask them. For pictures of the Dutch turbo see this pdf especially page 5. http://www.royalhaskoning.com/NR/rdonlyres/6EB9E06A-6846-4B3E-B4DD-2528675E78F6/0/Turborotondes.pdf 83.82.185.13 (talk) 17:18, 3 December 2008 (UTC)
It looks worse in plan view than it does to the driver. Print it out, lay it near the edge of a table, then look at it from a flat angle while kneeling next to the table. Then I think you'll see that, if properly designed and signed, they actually make sense.--Triskele Jim (talk) 17:34, 3 December 2008 (UTC)

Pedestrians?[edit]

Since when have pedestrians usually been banned from the middle of roundabouts? I've come across many roundabouts where it's common to cross the the center island, then to the destination road - particularly with many exits. On larger roundabouts it's common for the middle to be unsuitable, ie no pavements (sidewalks), walls, etc, but that's not the same as saying pedestrians are prohibited from there. Smaller ones less so. 128.232.228.174 (talk) 13:53, 13 May 2008 (UTC)

Pedestrians have been (usually) banned from modern roundabouts since forever. The top of the article has a list of differences between roundabouts and traffic circles. If a roundabout allows pedestrian traffic into the middle then it is usually a traffic circle.

from Roundabouts: An Informational Guide[1]:

2.2.1 Pedestrians

Pedestrians are accommodated by crossings around the perimeter of the roundabout. By providing space to pause on the splitter island, pedestrians can consider one direction of conflicting traffic at a time, which simplifies the task of crossing the street. The roundabout should be designed to discourage pedestrians from crossing to the central island, e.g., with landscape buffers on the corners. Pedestrian crossings are set back from the yield line by one or more vehicle lengths to:
• Shorten the crossing distance compared to locations adjacent to the inscribed circle;
• Separate vehicle-vehicle and vehicle-pedestrian conflict points; and

• Allow the second entering driver to devote full attention to crossing pedestrians

So, pedestrians are "banned" from the center island in modern roundabouts.Wvfd14 (talk) 16:43, 13 May 2008 (UTC)

No pedestrian access to the central island is the phrase used in the FHWA: Roundabouts an Informational Guide, guidebook.

I think a bigger issue related to pedestrians is the pending access board decision to require signalized pedestrian crossings at all multi-lane roundabouts where pedestrian facilities are provided. This would largely increase the cost of roundabouts, and make roundabouts tougher to justify. —Preceding unsigned comment added by 63.90.172.36 (talk) 15:08, 4 June 2008 (UTC)

Cornish Double Roudabouts[edit]

I think these curious aberrations would be worthy of mention, if anyone could explain the Cornish road planners' predilection for them. Bill F (talk) 22:07, 18 May 2008 (UTC)

I assume you are referring to some type of roadway geometry in the Cornwall region of Britain? I assume you mean something like this, but in the future I recommend that you provide examples. Also it sounds like you may have a personal gripe with them... please keep in mind WP:NPOV. I would expect that the engineers & planners that installed them had a good reason; and they likely continue to have a good reason considering that they are still there. --Bossi (talkgallerycontrib) 23:05, 18 May 2008 (UTC)
I don't think a conventional roundabout would fit in the location shown in Bossi's example, without taking the buildings on the northeast and southwest corners.Triskele Jim (talk) 17:14, 20 May 2008 (UTC)
The two circles could be merged to form an oval; this would make right-turns onto Fore Street longer, for little benefit that I can see. —Tamfang (talk) 06:09, 29 August 2008 (UTC)

Bossi, Cornwall is an English county, not a region. Your example does show what I am talking about. I do not need instruction on POV, thank you. Planners often have reasons, but not invariably good ones. How do you know the planners in question have not been fired? If references showed that some type of traffic control system were the subject of widespread opprobrium, would that not be legitimate article content? A merest tinge of humour in a talk page can occasionally help things along.

Triskele Jim, If there are space restrictions, I think you will find a single mini-roundabout is the more usual British solution. Bill F (talk) 23:08, 22 May 2008 (UTC)

I think this is meant with a mind towards where it would be beneficial to replace a simple staggered, oblique, multiple or otherwise complex intersection with a more controlled and equal-flow solution where the money isn't available to install and run traffic lights, but there isn't the space available (or again, the cash) to make the British Road Designer's favourite lazy-arse solution of whacking in a simple perfectly circular island big enough to allow all the connected roads to hit it in a roughly perpendicular manner with the minimum of other re-engineering. The alternative is a single wierdly-shaped roundabout, and this will have both lower overall capacity (for the same reasons as using the much larger-format Magic flavour), be more confusing to drivers, have issues with sight lines, lane paths, the need to drastically vary speed to make it around the tightest parts without holding everyone up on the straighter bits, etc. There's a few of these near where I live, and they're pretty lazy, awful solutions to a problem that shouldn't really have existed in the first place if a few more pounds had been invested. Whereas a few other similar junctions have double roundabouts (or even double really-big-"mini" roundabouts, oddly) and, once you've briefly adjusted to the idea, work just beautifully - more consistant speeds (themselves a factor in smoother flow), less overall conflict, better surety of what lane to be in as it's more likely you'll be allowed to pull across "between" the two islands, etc. 193.63.174.210 (talk) 19:53, 17 November 2008 (UTC)
Nothing aberrant about the double roundabout in the Bristol area. I can think of six straight away and they work just fine. I've never thought about the reason for them, I'll have a look when I go round one next - Adrian Pingstone (talk) 08:35, 23 May 2008 (UTC)
Where would you put a single mini-roundabout in the example shown? If it's in the middle, you get awkward acute angles between streets. —Tamfang (talk) 06:12, 29 August 2008 (UTC)
That simply looks like a double mini-roundabout to me. -- Trevj (talk) 12:54, 8 November 2012 (UTC)

What is this?[edit]

Just wondering, what is the proper name for this intersection?? --Admiral Norton (talk) 23:11, 22 August 2008 (UTC)

I'd call it a double roundabout, though the far part of it is unclear at this angle. —Tamfang (talk) 06:01, 29 August 2008 (UTC)
It's two roundabouts connected by a very short stretch of road. They serve together as one intersection in the grid plan of the neighborhood. Admiral Norton (talk) 20:17, 4 September 2008 (UTC)
On a larger scale, it could be a dumbbell interchange (see #Dumbbell and dogbone interchanges). In this case, it just looks like two mini-roundabouts (not really a double mini-roundabout because of the linking section). -- Trevj (talk) 13:00, 8 November 2012 (UTC)

Raindrops[edit]

The "raindrop" section is quite obscure. The pictures don't show enough to explain what's going on, and the text doesn't give me a mental image that makes sense. —Tamfang (talk) 06:01, 29 August 2008 (UTC)

AFAIK, it's a roundabout stretched like a peanut or a USB stick. Admiral Norton (talk) 20:18, 4 September 2008 (UTC)

Direction of rotation[edit]

Article currently reads (under Difference from traffic circles): All vehicles circulate around the central island in the same (counterclockwise) direction.

This is not true in Australia, where circulation is clockwise. I suspect the true situation is that it's clockwise in countries that drive on the left (e.g. Australia, UK), and anticlockwise in those that drive on the right (e.g. USA, France, Germany). Can anyone confirm for some other countries? Andrewa (talk) 16:29, 15 September 2008 (UTC)

You are correct: the portion in parenthesis reflected a RHD bias. The intent is that traffic circles sometimes have bidirectional flow around the central island. --Bossi (talkgallerycontrib) 01:13, 16 September 2008 (UTC)
Hmmm... But this article is quite explictly not about traffic circles. It's about roundabouts.
More important, what it says appears to be false. It's not bias, any more than it would be bias to say that all countries are monarchies. It's incorrect.
Several other articles already have the correct information, so I think we should just fix it. Andrewa (talk) 02:24, 16 September 2008 (UTC)
Fixed. Actually, the correct information was already implied elsewhere in this same article, in the caption of an image in the following section for example. Andrewa (talk) 15:18, 16 September 2008 (UTC)

Rotary?[edit]

I'm sure that this has come up a bunch of times, so I'm not going to just change the article, but at least a few New England states, Massachusetts being one of them, have Rotaries that are equivilent to Roundabouts, not Traffic Circles. That is, traffic already in the circle has the right of way. This article and the disambiguation page for Rotary should be fixed. CSZero (talk) 20:06, 16 October 2008 (UTC)

Additionally, I just found the archives for this article, and that lead me to the Portsmouth (New Hampshire) Traffic Circle. In the archives, there was a discussion about this particular interchange. Someone from Europe shot down the American who pointed out this is a Roundabout by the English definition (why we call it a traffic circle and not a rotary in this case is beyond me). His argument was because it doesn't have "yield lane markings." Well, in America, we don't have such markings, we have signs. And if you go to MSN maps and find the thing on the birds-eye view, you will see that little triangle yield sign saying entering traffic does in fact legally yield to traffic already in the circle. So... my point is that in many New England states, rotary means roundabout, and that the line between traffic circle and rotary and roundabout can get blurred to the point where I think we should merge the articles.
Someone pointed out in the traffic circle article that Massachusetts is actually trying to get rid of many rotaries, and this is one place where maybe a rotary does differ from a roundabout. We don't post many speed limit signs on the things, and some of them are massive "motorway" overpasses. In other words, we operate our rotaries with traffic-in-the-circle-gets-priority rules, but sometimes at speeds closer to 50 MPH than 25 MPH. CSZero (talk) 20:06, 16 October 2008 (UTC)
I'm obsessing and I need to go back to work :-) According to [2] which is an American publication that I found linked to this article, the New England Rotary is not a Modern Roundabout, but it is really not a traffic circle, either. If we don't clear this up by merging all of these into a single article, maybe the best bet is to create a seperate article for Rotary, to mean "Most common in the New England region of the United States, a rotary is primarily a mid 20th century roadway design defined as a circular, one way, often multi-lane roadway, similar to a traffic circle or a roundabout, but with key differences. They are often found as overpasses or underpasses to highways. Usually traffic already in the rotary has the right-of-way as in a modern roundabout and opposite of a traffic circle, although there are exceptions. The difference in design of a rotary versus a roundabout or a traffic circle, is such that rotaries tend to be quite large and there is little deflection around the central circle (meaning traffic coming on or off does so primarily in a straight line, not a curve). These two factors mean that rotary traffic often travels at speeds in excess of 30 miles per hour, leading to confusion and accidents, and the resulting unpopularity, that the modern roundabout does not suffer from. Although this is a traffic engineering definition, many rotaries are called traffic circles or simply circles, such as the Portsmouth Traffic Circle, in naming."
Does anyone oppose adding this article and updating the relevant pages to point to it? (and sorry for writing a novel in the course of a few hours!)
Thanks, CSZero (talk) 20:57, 16 October 2008 (UTC)
Alright, about a week and no comments or complaints, so I was Bold and went ahead and did it. CSZero (talk) 14:52, 22 October 2008 (UTC)

Offset roundabout[edit]

Offset roundabout

I just came up with this idea for an offset roundabout today, which would reduce the number and sharpness of turns required to traverse the roundabout. This way, if you're going right, you make a smooth right turn. If you're going straight, you just have to jog left and jog right. Has anything like this been implemented anywhere? It might take up a bit more space overall than a traditional roundabout since the approaching streets might have to be realigned (outside the boundaries of this diagram) to approach the circle as a tangent instead of directly. — Jonathan Kovaciny (talk|contribs) 21:56, 7 November 2008 (UTC)

Yes, very similar to an American Rotary (intersection). Please see: [3] for the example I photographed. CSZero (talk) 01:29, 8 November 2008 (UTC)
The entry curve is vital to the safety of a roundabout. It needs to be the sharpest to properly control traffic speeds. Sometimes a tangent exit is used, but tangent entries cause crashes.--Triskele Jim (talk) 21:51, 9 November 2008 (UTC)
I'm ambivalent ... on one hand the fast entry speed may disguise the fact the roundabout is there and otherwise encourage excessive entry speeds... on the other, the fact that it pipes you right into the outermost tangent of the curve puts you at least risk of doing so whilst being in direct violation of other vehicles (you only collide with those turning down the road to your right, rather than ANYONE going past the point where you lose it and crash over the more usual flanged bit), and if you can't handle the speeds of the exit curve, you probably won't have made it to said exit anyway. It puts me in mind of the dual-carriageway exits on british motorway junctions (particularly the one I take to get to work, where I'm pretty sure they added traffic lights with less-than-optimal phasing not for traffic flow control but simply to minimise exit speeds and prevent accidents, as you can still nudge the limits of grip from a standing red-light start if you push hard), but without the matching entry curve. Or indeed, at least in one direction it would be a lot like the one I just mentioned, as in at least one direction there's a "shortcut" lane to the motorway on-slip that first splits off from the other lanes, continues almost completely straight, then curves sharp left to join the main alignment. It's good fun to try and do it quickly when no-one else is around (as there are few physical barriers to just straddling the main curve of the roundabout in order to smooth off the sharpest turn), but all in all could do with alteration as doesn't do much to allow you a safe speed of entry to this fairly steep uphill bit of road (a slip road rising from a lower road to a motorway that is itself on maybe a 1:20 up grade) in either sense of the word.... i.e. you have to go slow in order to make the turn, then have nothing in reserve to build up a decent merging speed. Attacking it more shallowly from the standing start, or slower entry to the roundabout itself, would probably give you better odds, and be less likely to tempt an accident from entering far too quickly (70mph entry road, meet shortcut lane where you don't have to stop, and a sharp 2-lane turn where hitting it at 50 makes your tyres howl... with a big ol' concrete bridge support and embankment reinforcement waiting to catch anyone who misjudges it) —Preceding unsigned comment added by 193.63.174.210 (talk) 19:43, 17 November 2008 (UTC)
This is an interesting idea but would be dangerous! Assuming north is to the top, drivers travelling from the south to the east would have no deflection to force them to reduce their speed. They're supposed to give way to vehicles already on the circulatory carriageway. Therefore they would be in high speed conflict with drivers to their left also wanting to exit to the east. These drivers would be forced to brake, although in theory they should have the right of way while on the circulatory carriageway. Does that make sense? -- Trevj (talk) 13:08, 8 November 2012 (UTC)
It does ... makes sense to me. -- Gareth Griffith-Jones/The Welsh Buzzard 14:01, 8 November 2012 (UTC)

Questionable information in "Capacity" section[edit]

Quote: "A particular cause of congestion at a roundabout is when many motorists want to make a turn that effectively crosses oncoming traffic. The two images to the right, which presume right-hand traffic, show how opposing drivers making left turns will get into each other's path twice in a roundabout, but in most countries they will not cross paths at a conventional intersection. While always a potential issue, periods of low traffic density typically result in both drivers making simple adjustments to avoid each other and then going on their way. When traffic density crosses a certain threshold however, adjustments to speed and direction are no longer simple, and may not even be possible without circling the roundabout a second time, or even several times, in order to get a proper opening. And often, impatience overrules any inclination for said driver[s] to do other than "go forward"."

If two vehicles enter a roundabout at the same time to make a left turn in a right hand drive situation, they never encounter each other because they should be 180 degrees apart on the circle. If one enters before the other, and they do meet, the person entering must yield to the person already on. - simple.96.54.53.165 (talk) 05:31, 21 July 2009 (UTC)

I'm not sure if the author of this has actually used a roundabout or understands how they operate. There's no need to be extra careful or there being more danger when opposing right turns (for LHD, or left for RHD). The very nature of how a typical roundabout works - with either traffic entering the system, or less commonly, already on it yielding to the opposite kind - effectively turns it into a small, circular road where your only actions are to merge in and out safely and with proper regard to priority. It's no longer operating under the same rules as an opposing turn at traffic lights. In fact, even if there wasn't this definition and it was a big ol' free for all, it effectively reverses the way you cross the "oncoming" traffic, forcing you to go past, and then turn "nearside to nearside" after becoming clear of the oncoming vehicle, rather than "offside to offside" where you turn with them still in front of you, and still a potential danger should they decide to head straight-on at the last minute.

Also, just how badly are you getting it wrong (or how insanely densely trafficked yet somehow still fast-moving is it?) when you regularly need to execute two or more complete rotations of the island in order to carry out a simple turn? That shouldn't even be necessary on l'Arc de Triomphe. Somewhere, you have seriously missed the point and the method of approaching these things. I've had to do multiple circles once or twice before - but only because I'd lost my bearings, hadn't seen an approach sign, and was having to do a couple of moderately slow laps to read all the exit signs instead before choosing which direction to head. And once - once only - had to take emergency avoiding action and divert for a second go-around when cut off from my rightful path down the "fast" lane of a 4-lane road (from the middle ring of a 3-ring island) by some complete nobber who thought it perfectly alright to continue round to the next exit in violation of my lane without signals, acknowledgement of screeching tyres/horn/lights, or anything. Typically so long as you are at least partway intelligent about choosing your entry & exit points (e.g. in the above, don't intend on turning right from the left-hand lane on a clockwise rotation), use your mirrors and signals, and have a basic level of wit about you (optionally including that to gracefully recover from making a huge mistake in your intended path), it's a reasonably simple affair, even if it's not one that's guaranteed to be fast.

I really don't like having to write what feels like a flame at someone, particularly as I'm still on an anonymous account, but... damn, driving-noob. Do the research before writing? Yes, a large amount of cross-traffic preventing you getting onto the island in the first place can certainly cause congestion (and I've been stuck in a lot of it both when there's no gaps to be had, and behind people who can't identify the rare, cavernous ones), but the rest of it is wierd. 193.63.174.210 (talk) 19:32, 17 November 2008 (UTC)

Agreed. I just posted a substantial re-write of this section to address the points made above, which hopefully should remedy any bias issues.Bigfitz79 (talk) 00:54, 20 August 2009 (UTC)

"Deflection"?[edit]

Maybe this is a UK thing? I don't understand what "deflection" means in this article. It does not appear to be talking about Deflection (engineering), Deflection (physics) nor any other definition of the word I am aware of. 141.151.2.144 (talk) 02:17, 5 March 2009 (UTC)

It does assume a little bit about the reader's knowledge. I don't think it's a special UK use of the term, but the concept is a little weird. I'm going to edit the article, you tell me if it makes more sense now. CSZero (talk) 02:43, 5 March 2009 (UTC)
It means that the driver is forced to steer to change direction, and therefore has to slow down a bit before entering.96.54.53.165 (talk) 05:34, 21 July 2009 (UTC)
That's why the Offset Roundabout discussed above creates more problems than it solves. However, some roundabout in the UK provide a special lane for left turners (that's a 90 degree turn in a left hand drive situation) so that they don't have to mix in with drivers actually on the roundabout.96.54.53.165 (talk) 05:41, 21 July 2009 (UTC)
This was discussed in the archive. I meant to fix it then, and never did. Sorry about that. How about something like,
"Drivers must maneuver (are deflected) around the splitter islands and central island, at speeds of 15-25 mph (25-40 km/h). Many older traffic circles allow speeds as high as 45 mph due to insufficient deflection."
--Triskele Jim (talk) 16:37, 5 March 2009 (UTC)
I like it. Feel free to replace what I have, although maybe what I added with the specific bullet points different from traffic circles and rotaries should stay? CSZero (talk) 16:54, 5 March 2009 (UTC)

Another question...[edit]

What exactly is this: 45°46′38″N 15°57′10″E / 45.77722°N 15.95278°E / 45.77722; 15.95278? I'd say it's a rotary, but I'm not going to bet on it. Admiral Norton (talk) 18:25, 5 March 2009 (UTC)

I'm no expert but it looks like one. Compare to this one 43°04′23″N 70°46′51″W / 43.073049°N 70.780857°W / 43.073049; -70.780857
The one in Croatia is not a modern roundabout. It has a large diameter and weaving areas all around the circle, and it appears to be allowable to enter alongside circulating vehicles without yielding. More accurately this would be described as a rotary.Bigfitz79 (talk) 23:17, 19 August 2009 (UTC)
Google maps is out of date, evidently; even now it still shows the old Western Rotary, which has been replaced by a modern roundabout. --Una Smith (talk) 21:53, 11 December 2009 (UTC)
That is Remetinec Roundabout, and while it is sometimes possible to enter alongside circulating vehicles, any vehicle inside still has right of way, as full-white road lines mark all entrances into the circle, which means "stop and give way" in Croatian traffic law. So based on the definition of "rotary" where all entering traffic has priority, Remetinec is still a roundabout. --Joy [shallot] (talk) 09:41, 14 May 2010 (UTC)
The Portsmouth, NH circle is also a rotary by these same characteristics, despite being labeled in Google Maps as a traffic circle.Bigfitz79 (talk) 23:18, 19 August 2009 (UTC)
For what it's worth, signage on the Portsmouth Traffic Circle refers to it as a traffic circle. It too is a very wide, high speed circular roadway with no lane markings, and vehicles weave around each other. --Una Smith (talk) 21:53, 11 December 2009 (UTC)

Yield to the left or yield to the right?[edit]

Roundabouts work when the rule is that you always yield to a vehicle already on the roundabout. In a right hand drive situation, this means that you yield to a vehicle approaching on your left when entering a roundabout, and is opposite to the usual rule for other kinds of intersections where you yield to vehicles on your right. However, the British Columbia Driver's Manual states that if two vehicles arrive at a roundabout simultaneously, the entering driver should yield to the vehicle on his right. Mostly there's no problem if both enter simultaneously, since they are separated by 90 degrees of the circle but can create some dicey situations if the driver on the right judged himself to be "simultaneous" and the driver on the left judged himself to have arrived first. In right hand drive, the rule for roundabouts should always be yield to the left.96.54.53.165 (talk) 06:07, 21 July 2009 (UTC)

If both arrive at the yield line simultaneously from two different approach directions, they should both be able to enter at the same time with no conflict because there is enough room. But lets assume both are very long vehicles or it's a very small roundabout. Assuming that we're in a country where people drive on the right, both drivers have "yield" signs, and both are supposed to yield to the vehicle on the left, but only one of these drivers has a vehicle to their left. The yield-on-right rule is for uncontrolled intersections, and a roundabout is not uncontrolled, it is controlled by yield signs.Bigfitz79 (talk) 23:22, 19 August 2009 (UTC)

American vs. British English[edit]

I'm guilty, I failed to observe that this article was written exclusively in British English, and I should have abided by that when making edits. I do want to appeal that although words like "signalised" and "junction" are readily understandable in American English, other terms such as "level crossing" are uniquely British and not widely understood in North American usage. The Manual of Style gives clear guidance on language when a topic is relevant to a particular region (such as the Australian Defence Forces or American Civil War) but unfortunately roundabouts are a much more global topic and the guidance is not nearly as clear except to accommodate both wherever possible. Additional edits and discussion on how to reach a globally-understandable article are welcome. Bigfitz79 (talk) 20:28, 25 August 2009 (UTC)

   Reference simply to WP:MoS may lead some to consult simply WP:MoS#Stability of articles, while the same page's section WP:RETAIN is specifically pertinent.
----Jerzyt 00:19, 23 May 2011 (UTC)

At the beginning of the article, it states "roundabout" is a British term. What is the American name? Signs here in Missouri, and general usage, is "roundabout," although in other parts of the US they are called "rotaries" or "traffic circles." Should the statement that its a British term be removed? — Preceding unsigned comment added by 75.28.54.72 (talk) 15:10, 17 September 2011 (UTC)

No, because it is still predominantly a British term. It's like how most Americans understand that "lorry" is the British term for truck, but don't use it themselves and find it exotic when British people use it. However, unlike lorry, there's no different word used in American English; Americans simply borrow the British term when they need to. --Coolcaesar (talk) 11:16, 18 September 2011 (UTC)

Anticlockwise = counterclockwise.[edit]

As roundabouts are becoming more popular in the US - and especially since 4 of them are being installed on consecutive intersections of a busy highway in Irondequoit, NY (just NE of Rochester), with one of them being right near a school - I am thinking that some folks around here may be coming to this article to find out about these roundabouts.

So, yes, I believe that a quick explanation like I just inserted about Brit "anticlockwise" being equivalent to US "counterclockwise" is warranted, and does not hurt the article's Brit flavor.

(There's some less-than-sharp folks around these parts driving automobiles, and they need everything spelled out for them like this!)

Manburger 486 (talk) 12:42, 21 September 2009 (UTC)

I have no problems with both terms being there. Last time though, you replaced one with the other, which would be against the policy of keeping the page in one dialect of English. Thanks and happy editing,
--CSZero (talk) 15:07, 21 September 2009 (UTC)
The following contrib appears to have addressed Manburger rather than CSZero, and to have had its indentation blindly increased another step in replying. On that assumption, I have ex-dented it and the succeeding contribs by one step, in the interest of clarity.--Jerzyt 01:00, 23 May 2011 (UTC)
Do you really not know the meaning of the word "anticlockwise"? ...and can you not figure out what it means instantly, just from seeing it? I assume you know what "anti-" means. I object to the idea of explaining every little word to people in an encyclopaedia.
--(Huey45 (talk) 13:23, 30 April 2010 (UTC))
If you read what he said carefully, you'll note he wasn't talking about himself, unless you're not assuming good faith for some reason. (Also note that the post was written 7 months ago.) There is nothing wrong with explaining something in its first usage, and in a later section if they are far apart. Explaining things is an encyclopedia's job, and a large part of WP's readership is not fluent in English, even those for whom English is supposed to be their first language. Should both words be used at every occurence? Of course not, but it should be done at least once where needed. - BilCat (talk) 13:50, 30 April 2010 (UTC)
Americans are stupid. —Preceding unsigned comment added by 2.99.20.223 (talk) 05:14, 24 March 2011 (UTC)
   As i just noted in the preceding section #American vs. British English, discussants here may have consulted the first relevant section of the cited guideline page. But wp:RETAIN strongly suggests that consideration limited to the issue of spelling is what has been so exhaustively weighed as to deserve the summary near the top of the guideline; that summary is not precise enough to clarify whether the slightly broader principle stated there was intended to be broader, and to include (as could be argued) the infrequently contested matters of "style" that go beyond the once vigorously contested (and still frequently misunderstood) matter of our approach to spelling.
    I replaced
anticlockwise (counterclockwise)
with
anti- (or counter-) clockwise
in the process of eliminating the redundant link. My reasoning in not eliminating "counter" is that spelling differences seldom interfere with communication, as they look at worst like misspellings of specific familiar words, while many of the usages of "anti[-]" and "counter" are so different in thrust (one who counts; that which acts as a substitute in counting; horizontal work-surface for a standing person) that a (non-stupid) AEng-speaker who has never bothered to analyze "counterclockwise" may require more than a few instants to understand.
--Jerzyt 01:00, 23 May 2011 (UTC)

Basin Reserve example[edit]

I support Bigfitz79 having deleted the Basin Reserve example for the reasons stated. Schwede66 (talk) 23:22, 3 November 2009 (UTC)

Organization[edit]

Just a couple comments I might try to do something about:

  1. "Advantages and Disadvantages" makes for bad organization of an encyclopedia page - all of that content should align with various performance characteristics.
  2. Like half of the article is spent going through a litany of bizarre variants on the roundabout idea. I imagine that could be fairly confusing, as most of these do not in fact meet the definition of a roundabout.
  3. Do we need four pictures of signs?
  4. About 72% of the world's total road distance carries traffic on the right, and 28% on the left. Should we switch the animation?

MakeBelieveMonster (talk) 04:28, 21 January 2010 (UTC)

Rotary merged into Traffic circle[edit]

The two terms are synonymous, so their articles have been merged. For consistency, we should generally use "traffic circle" in place of "rotary" now. MakeBelieveMonster (talk) 04:46, 21 February 2010 (UTC)

It's not that simple. Please see discussion at Talk:Rotary (intersection). CSZero (talk) 06:26, 22 February 2010 (UTC)

Lead[edit]

A roundabout is not the same as a rotary or traffic circle, from an engineering perspective. That much is absolutely clear. As far as colloquial usage, this is already addressed in the article in pretty reasonable way. MakeBelieveMonster (talk) 23:48, 30 April 2010 (UTC)

It seems you don't know how modern dictionaries are made. Please do not remove well-sourced info from reliable sources. Please take a look at Wikipedia_talk:Manual_of_Style#target_audience_.2F_respect_for_dictionaries before responding or editing. In addition, even the article's source http://www.tfhrc.gov/safety/00068.pdf says "roundabouts and other forms of traffic circles", in other words considers a roundabout a kind of traffic circle. WP cannot ignore the most widespread English usage as recorded in major dictionaries even if experts in the field use a word in a restricted sense. The reader needs to know in the first sentence what the article is about. As the dictionaries show, "roundabout" is still considered a UK term by most printed sources, and a roundabout is still usually called a "traffic circle" in US printed sources though these may add a qualification like "modern" to it. --Espoo (talk) 08:22, 10 May 2010 (UTC)
These odd terms are pretty much *only* used in the US - I hadn't even heard of a "rotary" as anything other than an outdated form of telephone until this conversation, and I'm not in the UK. The additions are a misuse of the lead, in my view, to push a point of view (see WP:WEIGHT) and this should be discouraged. Orderinchaos 09:37, 10 May 2010 (UTC)
Well-established WP policies, WP:ENGVAR and Wikipedia:Lead section, definitely not pushing a point of view. --Espoo (talk) 09:56, 10 May 2010 (UTC)
Scholarly sources use "roundabout": [4] [5] [6] [7] [8] [9] [10]. Not only in the UK. Everywhere. Colloquial usage was already addressed in the article, but now it is given undue weight. Calling a roundabout a "traffic circle" or "rotary" is not a matter of dialect; it is incorrect.
MakeBelieveMonster (talk) 20:17, 10 May 2010 (UTC)
1) Your links are almost all to European sites, which is illogical since no one is disputing that UK English uses "roundabout" or that other Europeans tend to use UK English when writing in English.
2) The only US site you linked to has plenty of pages that use "traffic circle", many or most of which do not even mention the term "roundabout" in their abstracts. See, for example, the first five search results: [11], [12], [13], [14]], and [15].
3) Even if US engineers had completely dropped use of the term "traffic circle" to refer to "modern traffic circles" or "modern roundabouts", we would still need to mention in the first line what these things are called in everyday life in the US both in speech and the media and in general publications, which is what dictionary entries in modern dictionaries are based on. --Espoo (talk) 14:01, 12 May 2010 (UTC)
Soooo, the Transportation Research Board is based in Washington, D.C., which is the US capital. This accounts for five of the sources. The International journal of industrial ergonomics also seems to be US-based, though it's unclear. The main point is that the term is used by everyone who wants to be taken seriously academically.
The counter-examples you provide are dealing with things other than roundabouts. For example, the Latham Circle which is covered here [16] [17] is a traffic circle and not a roundabout. Your examples from Australia [18] and Germany [19] are most likely dealing with real traffic circles as well - it's hard to tell. But I'm by no means denying that traffic circles exist.
Finally, the article already had mention of colloquial terminology prior to your additions. it said "Roundabouts should not be confused with older designs such as traffic circles, which typically are larger, operate at higher speeds, and often give priority to entering traffic[1]." By writing that roundabouts are "usually called a traffic circle" you are confusing the article unnecessarily.
MakeBelieveMonster (talk) 15:10, 12 May 2010 (UTC)
You really don't get it - these things are called "traffic circles" by 99% of people in North America, so we definitely need to mention that at the very beginning of the article. We can go on to explain that experts call them something else, as we do. WP is not an engineering encyclopedia which can try to make its readers, i.e. experts in the field, use terms as defined by the profession. WP is not in the business of telling people how to speak English, and a good, i.e. modern engineering encyclopedia would start just as we do here, listing the specialist term first and then explaining what most people call the same thing, even if this is considered incorrect by experts.
The word "roundabout" sounds really strange and quaint to US ears and will perhaps take a long time to catch on if ever. Usually North Americans are quick to adopt terms presented by experts for new things, so it seems this time the experts either chose a term most people really dislike or most people don't feel a new term is necessary for something that is more or less the same thing in the eyes of non-experts.
And your links were 1 ictct.org, 3 cat.inist.fr, and 3 trb.org, so 4 of these 7 proved nothing about US usage. And yes, i knew that trb.org is a US site, which is why i provided you with search results from that site showing use of "traffic circle". And Germany has had only modern traffic circles ("roundabouts") for a long time, so the expert who wrote that paper is probably talking about them using a term that you perhaps incorrectly claim is no longer used for modern traffic circles by experts. --Espoo (talk) 21:06, 12 May 2010 (UTC)

──────────────────────────────────────────────────────────────────────────────────────────────────── The three articles on cat.inist.fr are from the TRB and the International journal of industrial ergonomics. I was just taking the first google hit. Also, I would point out that this article is in UK English if you're still unconvinced the term is correct in the US.

As a more general response, I think people come to Wikipedia to learn something. And I think we do them a disservice to say "toads are usually known as frogs." There is an important distinction between roundabouts and traffic circles... but I think we've reached an impasse. Would any other editors like to comment on this topic? MakeBelieveMonster (talk) 22:46, 12 May 2010 (UTC)

Having looked at both this (both lead versions) and Traffic circle, and having driven plenty in the US, UK and Europe, I am pretty much confused. If there is a distinction between popular usage and that of professionals, this should be spelled out as such. The two articles give definitions that seem to have so many exceptions that there is considerable overlap. That also may need explaining. Is B. Guichet, with his claim of French numerical superiority, an RS I wonder? It seemed a most surprising claim to me. "Traffic circle" seems a wholly US article, & should probably say so at the start. Roundabout may need a 2nd section distinguishing different types & different terms & usages, keeping this stuff out of the lead, especially the first sentence. But US terms, both popular and technical, should certainly be covered. Johnbod (talk) 02:49, 13 May 2010 (UTC)
Yes, i've been planning a merger proposal because even experts consider and call roundabouts a kind of traffic circle. The problem is essentially very simple: There are old-style and new-style traffic circles and engineers and bureaucrats want to get people in the US to use a new term instead of simply saying "modern traffic circle" because old-style traffic circles have a bad reputation and new ones are opposed by most people in most countries until they get used to them. The new term and the new kind of traffic circle happen to be in use in the UK but North Americans apparently consider the term "roundabout" quaint and foreign and it hasn't caught on yet. Engineers and bureaucrats and some WP editors have an agenda here and are trying to force the new term down people's throats.
And MakeBelieveMonster, if dictionaries said that people usually use "frog" for what experts call "toad", WP would definitely have to explain that. --Espoo (talk) 09:04, 13 May 2010 (UTC)
Johnbod, when you say that traffic circle "seems a wholly US article" do you mean the terminology or the type of intersection being described?
Espoo, I would be agreeable to making Roundabout a daughter article of Traffic circle if you have direct sourcing for that. But currently I've only heard the quote saying "roundabouts and other types of traffic circles..." which is not strong enough to base an article off of.
Finally, I have to dispute the first sentence claim that roundabouts are "usually called a traffic circle, circle, or rotary in North America." The sources provided are dictionary definitions of "roundabout" that do not mention "traffic circle" or "rotary" at all. There is one definition for "rotary" which actually defines it as a roundabout. But the sources do not support the claim.
MakeBelieveMonster (talk) 12:02, 13 May 2010 (UTC)
Well those, and nearly all the examples, pictures etc. And isn't the last picture, with a "Yield" sign, actually a roundabout? I'm not sure I'd favour a merge though; this page is long enough already. But the differences in usage need to be more clearly stated. To state the obvious, both "traffic circle" and "rotary" are entirely unknown terms to British popular usage, I don't know about Canada, Australia etc. On the last point above, as I have been explaining to Espoo on another page, dictionaries are not intended to be used to decide questions such as which of two terms is more "usual", and are a bad way of doing this. Johnbod (talk) 13:06, 13 May 2010 (UTC)
Roundabout is the most common term for this type of junction worldwide, if residents of the US choose to call them something different then that is their beef. By all means merge traffic circle into this article as they are essentially the same but with slightly differing priorities, but the reverse is outright stupidity and an example of a US-centric POV. Jeni (talk) 13:19, 13 May 2010 (UTC)
Johnbod and MakeBelieveMonster, on the contrary, the dictionary sources provided in the first ref note definitely show that "traffic circle" is the word used in North America for what in UK English is called "roundabout". And dictionaries are most definitely usually the best way to decide which terms are more usual in a certain kind of English and in all kinds of English. The editors of US and UK dictionaries use and read about traffic circles / roundabouts very often, so there is very little chance that they would not have updated their definitions if things had changed significantly.
Johnbod, it's simply not reasonable to claim that the work of dictionaries on their text corpora and these corpora themselves are useless and unreliable because of a quibble you have about the fairly obscure decorative arts term "cloisonné", which most dictionary editors do not run into often. Modern traffic circles are being built all over the US right now and the media is full of the buzzword "roundabout" that the engineers and bureaucrats are trying to establish to sell them to the very reluctant public, but apparently most people and printed sources, including the media, still prefer the term(s) "(modern) traffic circle".--Espoo (talk) 14:19, 13 May 2010 (UTC)
That's not the point, or the main one anyway. Dictionaries start with a word, and tell you what it means, often using other terms in the course of this. Dictionaries are not designed to help you choose between different terms for the same thing, ie to start with a meaning and then find the best word. Generally they only offer inferential evidence for this; they simply don't include this in their aims in most cases. When there is a distinction between terms accepted by some speakers but not others they are supposed to cover all possible senses but, if they go into the different types of usage, it will normally be only in very vague terms - "especially" is a favourite word. It is precisely because dictionaries don't "prescribe usage" that they are of little use in choosing between alternative terms. They are also not updated as regularly as you seem to think (at the single entry level), and may be out of date when usage is on the move. A lot of effort is expended fixing new word/sense entries, but once included they normally are not revised for decades. When were the definitions you refer to last changed? If there is a "battle for the word" going on in the US, that is well worth adding, with references, which ought to findable if things are as you say. The current opening clearly does not work, because it blurs the distinctions between the two types, and the usages of terms for them. This needs to be expanded on in the section below, not in the first sentence:
"A roundabout, usually called a traffic circle, circle, or rotary in North America (though "roundabout" is used by engineers in North America too),[1] is a type of circular intersection in which traffic must travel in one direction around a central island.
These junctions are sometimes called modern roundabouts in order to emphasise the distinction from older circular junction types which had different design characteristics and rules of operation."
To say, of the US:"the media is full of the buzzword "roundabout" that the engineers and bureaucrats are trying to establish to sell them to the very reluctant public" considerably undercuts your case, and contradicts various other assertions you have made elsewhere in the discussion & edit summaries about the term being "unknown" etc in the US. Johnbod (talk) 15:33, 13 May 2010 (UTC)
I've taken a shot at making the lead reflect our discussion and the actual sources. I don't think the dictionary sources are sufficient to say what word people "usually" use, but I left some text that "traffic circle" gets used sometimes. MakeBelieveMonster (talk) 19:01, 13 May 2010 (UTC)
Better, but rather than:"In some cases, the term "traffic circle" has been used to describe roundabouts in North America,[3] but generally "roundabout" is used by engineers" would be "The term "traffic circle" is often still used [by the public] to describe roundabouts in North America,[3] but generally "roundabout" is used by engineers", which I imagine can be supported by refs. I'd still expand the 2nd section on usage of terms. Johnbod (talk) 19:20, 13 May 2010 (UTC)
If the US usage of terms really is that confused, it may be a good idea just to say, bother here and at "traffic circle", something like "this article deals with A, B is covered at...". We are entitled to define the scope of articles, so long as it is made clear that some usage may be different. Johnbod (talk) 12:51, 14 May 2010 (UTC)
Wow, this was quite a read. I'd like to preface this by saying that I am a traffic engineer who deals extensively with roundabouts, including in an international context, and I assure you that I am very familiar with this topic. I have also provided edits to this article in the past, but left it alone for over a year, in part due to frustration. I want to set the record as straight as I can on this issue. First, there is no official globally adopted uniform definition of "roundabout", "modern roundabout", "traffic circle", or "rotary", at least not yet. I strongly disagree though with the assertion that "99%" of Americans refer to them as traffic circles. That may be true in a particular locality, especially where other circular junctions exit, but it is by no means a national pattern. I know of no state Department of Transportation, advocacy group, municipality, or anything that uses the term "Traffic Circle" to refer to a modern roundabout in any official context. Some people do call them traffic circles, but that is changing, and it was never a prevailing national usage as asserted by this thread. That said, even if the terms are murky and sometimes used interchangably, there are distinct, clear, verifiable differences between these types of junctions, and I think it is a disservice to readers to condense them all into a single article. If they are, they should be grouped under an over-arching heading such as "Junctions featuring center islands", which is admittedly a mouthful. I wouldn't even want to call them circular junctions because they're not always circular, nor do they all have continuous loop roads, circular or otherwise. The lack of official definitions is a problem, but I am now resolved to clean up this article as it has become extremely confusing and scattered, and seems to focus predominantly on rare oddities such as rail crossings. It'll take a while.Bigfitz79 (talk) 01:42, 17 March 2012 (UTC)

Lies, damned lies, and statistics[edit]

    I found

Now, there are about 2,000 U.S. roundabouts as of 2010, and their number grows rapidly.<ref name="Keh 2010" />

which had the count changed (while i was editing the lead section) to 2,300 (without removing the old ref that does say "2,000", nor changing the year to reflect what the colleague's ed-summ claims). (But contrary to my ed-summ, i did not overwrite the change in an edit conflict, because the edits overlapped only in time, not in both time and space). Subsequently, i replaced that with

In 2010, there were about 2,000 U.S. roundabouts,<ref name="Keh 2010" /> and their number grows rapidly.{{Vague|date=2011 May|Reason=without a source *that gives concrete info as to why* its author said "rapidly", this is worthless PoV}}

I decided not to insert

... and 2,300{{Fact|date=2011 May}} {{as of|2011 1st or 2nd quarter|lc=yes}...

because then "about 2,000" invites essentially the same reaction as "2,001" would, namely,

+299 in 6 months, that's 30% per year!

which is unjustified since (to take an extreme case) 2,400 is also "about 2,000", and could indicate a significant number had been demolished in the period in question.
    For my money, a new # without a reliable source is not as valuable as an old one with. And the combination of the two is worse than either alone, bcz it suggests we think 2 numbers are better than one and thus serves to endorse making unjustified conclusions about the growth rate.
--Jerzyt 02:32 & 02:37, 23 May 2011 (UTC)

Baffled[edit]

I am really baffled by this article. When I learned to drive, decades ago, one of the rules was that traffic that is already in a traffic circle has right of way over traffic that is entering. This is only logical; I assume it should be obvious that if traffic in the circle were to yield to traffic entering, then you get gridlock as soon as the traffic circle fills up? The opposite rule would have been insane. Now, apparently, there's a new name for traffic circles in which traffic that's already on it has right of way, it's called a "roundabout," and they have decided that it is something new invented in the mid 20th century. By the way, the citation for this is a broken link. Geoffrey.landis (talk) 19:53, 4 July 2011 (UTC)

I've made an attempt to clear up the article and make it a little more clear that the roundabout was not, in fact, something invented in the mid 1960s. Much of this was simply moving the history section up to the beginning (it's better there anyway), and making some new section headings.

I'm still baffled by some things. For example, "The first modern roundabout in the United States was constructed in Summerlin, Nevada in 1990 [20]". Huh? As far as I can tell, the only defined difference between a "traffic circle" and a "modern roundabout" is the rules used for traffic flow. So, any traffic circle can be roundabout if you apply new rules. I'm not even sure what it means to say they "constructed" a roundabout that's different from a traffic circle, since a roundabout is identical to a traffic circle in everything that is constructed. The article is saying that no traffic circle anywhere in the US had rules of entering traffic must yield until a brand-new circle was built in Nevada in 1990? I'd like to see a better citation for that.Geoffrey.landis (talk) 20:18, 4 July 2011 (UTC)

No, if you read the U.S. technical literature on roundabouts, the other major feature is their carefully defined geometry. Entries to modern roundabouts are meticulously designed to force drivers to slow down and pay attention as they merge into the roundabout. In contrast, cars can just carelessly roll straight into traditional three-way or four-way intersections in front of perpendicular traffic, resulting in nasty "T-bone" accidents which roundabouts are supposed to reduce. Most traffic circles don't have the lane narrowing and sharp right turn seen on entries to modern roundabouts which forces inbound drivers to slow down.
I personally find modern roundabouts annoying and a sign that the local municipality is too cheap or too poor to afford a proper stoplight, but I have to admit that their geometry does work in terms of making me pay attention to where I am going.--Coolcaesar (talk) 03:18, 5 July 2011 (UTC)
It may be true that the difference between a traffic circle and a "modern roundabout" is that the modern roundabout has a "carefully defined geometry," but this is not very useful in distinguishing one from the other. For example, consider the roundabout visible on maps.google.com at latitude/longitude 41.511683,-81.614717 . This clearly does not have the "sharp right turn" you mention. Is it a "modern roundabout" or is it a "traffic circle"? How about this one, in Newburyport: 42.798935,-70.875442 -- "modern roundabout" or "traffic circle"? What is the defining feature? Geoffrey.landis (talk) 18:39, 5 July 2011 (UTC)
Those are not modern roundabouts; they were clearly built back in the 50s or 60s or even earlier. A good example of the tight geometry of a modern roundabout (built around 1998) is at coordinates 37.3305,-122.0806 in Cupertino, California. Notice how every car entering this intersection MUST slow down and pull hard to the right to go around the roundabout, or else risk skidding out of control. --Coolcaesar (talk) 13:40, 13 July 2011 (UTC)

Disadvantages[edit]

POV? Any reason why we have advantages but no disadvantages? What might be a disadvantage? -land area required -pedestrian crossing (no gaps in traffic) -"weaving" in multilane roundabouts -all traffic has to slow (example of high volume road meeting low volume road, everybody on high volume road has to slow down)

Multilane Roundabouts[edit]

I'm a bit confused about how to navigate two or three lane roundabouts. I tend to all the way around in the outside line. In Euro or American "drive on the right" system how would I make a "left" turn Who has right of way inside the rondo? e.g. if one car is in the "inside" lane and one in the "middle" lane who has ROW? Any studies on capacity versus number of lanes?

You are not the only one confused by this, but from what you describe, your behavior at a roundabout, driving all the way around in the outside lane, would generally be illegal and hazardous at roundabouts in many countries including the USA, Canada, the UK, Ireland, Australia, and New Zealand. In these countries, exiting a roundabout is, with rare exceptions, a "straight-out" movement and NOT a turn. Therefore, exits may generally be made from the inner or the outer lane, and exiting traffic has the right-of-way. However, you MUST choose the proper lane before entering. To make a left turn (in drive-on-the-right countries), this means keeping to the left (nearer to the center island) as you approach and as you drive through the roundabout.
By contrast, roundabouts in Spain, Germany, Slovenia, and the Netherlands use a "turn-out" design in which exiting the roundabout is always a right turn. Under this design, exits may normally be made from the outer (right-hand) lane only. In these countries, going all the way around in the outside lane is acceptable, and you need not choose a particular lane before entering. When multi-lane roundabouts are built in these countries, the inner lane tends to be rarely used, and the circle must be much larger for multi-lane roundabouts to accomodate lane shifts within the circle. The Turbo Roundabout is sometimes used in these countries to force the outer lane to make a right turn and exit the roundabout, thus allowing the inner lane to also exit which would otherwise be very difficult in these countries.
This article is a mess, and hard to understand, because of these two competing designs and the lack of an official definition from the engineering profession. I've stepped away from this article for a while, but I'd like to do some major edits at some point to address these two competing designs.Bigfitz79 (talk) 21:20, 16 March 2012 (UTC)

Dumbbell and dogbone interchanges[edit]

See Talk:Bowtie (road)#Dumbbell interchange. --Chaswmsday (talk) 21:28, 13 October 2012 (UTC)

The Onion[edit]

Transportation Secretary Ray LaHood reportedly spent three hours this weekend proofreading, correcting, and in some cases rewriting Wikipedia’s error-riddled roundabout entry. “Oh, come on, who edits this stuff?” said LaHood, shaking his head while deleting a “completely erroneous” paragraph from the section on marked-perimeter cycle lanes." (Source: The Onion) — Preceding unsigned comment added by 72.130.207.186 (talk) 22:01, 30 October 2012 (UTC)

Oh? So where are they? Not in 'the history' ... (funny) ... Ha, ha! -- Gareth Griffith-Jones/The Welsh Buzzard 10:34, 31 October 2012 (UTC)
"Funny", yes I agree. Obviously this is because The Onion is based on satire. -- Trevj (talk) 11:23, 8 November 2012 (UTC)
Diolch yn fawr, Trevj. Iechyd da! -- Gareth Griffith-Jones/The Welsh Buzzard 11:38, 8 November 2012 (UTC)
Dydy'r defnyddiwr 'ma ddim yn deall y Gymraeg. Google Translate's a help, though. Iechyd da! -- Trevj (talk) 13:17, 8 November 2012 (UTC)
Nid yw hyn defnyddiwr. Rwy'n meddwl fy mod yn gweld blwch defnyddwyr sy'n dweud yn wahanol. -- Gareth Griffith-Jones/The Welsh Buzzard 13:25, 8 November 2012 (UTC)y
Rwy'n gweld nawr: mae sero. -- Gareth Griffith-Jones/The Welsh Buzzard 13:28, 8 November 2012 (UTC)

Mention the worlds largest roundabout[edit]

Mention the worlds largest roundabout, preferably in its own section. If there is no undisputed one, mention that fact instead. Jidanni (talk) 12:44, 16 November 2012 (UTC)

Okay, why? —Tamfang (talk) 03:20, 2 December 2012 (UTC)
... and who is going to bother to measure it? Ha, ha! -- Gareth Griffith-Jones/The Welsh Buzzard 10:42, 2 December 2012 (UTC)

On whether a traffic circle is different from a roundabout[edit]

I'm still seeing all evidence here that the distinction between a traffic circle and a roundabout is just a WP:ENGVAR difference elevated into a phony distinction. The key claim that they are different is uncited, and discussion above suggests that it's uncited because its not a real distinction. If someone can come up with a technical reference that distinguishes the two, I'll be happy, but otherwise I'm going to move for a merge. Mangoe (talk) 22:49, 30 January 2013 (UTC)

Speaking as a Brit, I am not in any way familiar with the expression "traffic circle" and I have clocked up over 70 years. Therefore, Mangoe you have my
  • Strong oppose It's not an ENGVAR thing, they're not the same thing, even in the USA, which has both. A roundabout has the roads coming in radially, whereas with traffic circles they're nearly always entering circumferentially. Roundabouts are much safer and are a different shape, and have different properties.GliderMaven (talk) 03:10, 31 January 2013 (UTC)
Your answer pretty well illustrates why I'm inclined to lump this all together. If you look at this historical account, they call the circumferential entry variety a "rotary". But they also say that the British changed the way their roundabouts worked starting in the 1960s. In other words, they aren't consistent themselves: a roundabout means an circular intersection governed only by the "yield to traffic in circle" rule, and nothing else, except before that, when it didn't mean that because (from what I can tell) the Brits never used the phrase "traffic circle". So British roundabouts may or may not be traffic circles, depending on the timeframe, but American roundabouts are, if you are a highway engineer, never traffic circles because the CE guys adopted the Brit terminology after the Brits settled on one way of doing it. Mangoe (talk) 04:32, 31 January 2013 (UTC)
Totally agree with Mangoe's post immediately above this – Gareth Griffith-Jones – The WelshBuzzard – 09:34, 31 January 2013 (UTC)
Strongly disagree. Having driven roundabouts on four continents as well as roundabouts, traffic circles, and rotaries all over the U.S., including the Los Alamitos Circle, Columbus Circle, and the De Soto Fountain circle (just to name a few), I have personally experienced the significant differences between roundabouts, traffic circles, and rotaries. Anyone who has survived the wildly dangerous traffic on a typical poorly-designed New England rotary would not consider it remotely equivalent to a modern roundabout. --Coolcaesar (talk) 14:18, 31 January 2013 (UTC)
So the key difference is that rotaries / traffic circles are badly designed? —Tamfang (talk) 18:50, 31 January 2013 (UTC)
... are badly designed roundabouts.
 – Gareth Griffith-Jones – The WelshBuzzard{{spaced ndash}17:59, 1 February 2013 (UTC)

Other uses for raindrop roundabouts[edit]

The current wording of the raindrop roundabouts section implies that these occur only at interchanges - largely or wholly synonymous with the dogbone interchange. Could these also be used for at-grade intersections, perhaps tending toward a hybrid between a Michigan left and side roads accessed by right-in/right-out turns? Could they be seen as a "squashed" variation on a roundabout interchange? Could they appear in other uses? --Chaswmsday (talk) 00:54, 23 February 2013 (UTC)

...there is less weaving in a turbo, making entering and exiting more predictable. Because there are only ten points of conflict (compared with 8 for a conventional single lane roundabout, or between 32 and 64 with traffic signal control)... That's two more not fewer points of conflict. I'm guessing that this is a mistake. What should the numbers be? — Preceding unsigned comment added by 146.90.242.216 (talk) 09:26, 1 April 2013 (UTC)
Which has what to do with raindrop roundabouts? --Chaswmsday (talk) 14:59, 7 April 2013 (UTC)