AskDefine | Define gyratory

User Contributed Dictionary

English

Pronunciation

  • /ˌdʒaɪˈɹeɪt.ə(ɹ).i/ /%dZaI"reIt.@(r).i:/ a UK
  • \Gy"ra*to*ry\

Adjective

  1. Moving in a circle, or spirally; revolving; whirling around.

Derived terms

See also: rotator

Extensive Definition

A roundabout is a type of road junction at which traffic enters a one-way stream around a central island. In the United States it is technically called a modern roundabout, to emphasize the distinction from the older, larger type of traffic circle.
Overall, roundabouts are statistically safer than both traffic circles and traditional intersections, with the exception that cyclists have a significantly increased crash rate at large roundabouts. Roundabouts do not cope as well with the traffic on motorways, highways, or similar fast roads.

Difference between roundabouts and traffic circles

Roundabouts are sometimes referred to as "traffic circles" or "rotaries", but a technical distinction was made in some jurisdictions between roundabouts and traffic circles in the mid-1960s. Starting in that decade, research in the United Kingdom found that circular intersections with certain geometric characteristics and traffic control schemes tended to be safer than those without them. The key differences are: The United Kingdom does not have any traffic circles as defined above, nor is the term used there; it only has roundabouts (and variants such as mini-roundabouts and magic-roundabouts — see below). In the United States, circular intersections that meet the design standards shown in the table above are termed "modern roundabouts," to distinguish them from older rotaries or traffic circles. In Massachusetts and other New England states, roundabouts (or traffic circles) are called rotaries (the sign says ROTARY, with an arrow on the sign). Also, in Massachusetts, rotaries are nearly always built to the standards of a British roundabout, and a "roundabout" refers to an especially small rotary with crosswalks, between high-traffic roads.
Seattle, Washington has well over 100 roundabouts that have been built over the last two decades, with many more located throughout the Seattle Metropolitan area. In addition, hundreds of mini-roundabouts have long existed in the city's residential neighborhoods.

History

The first roundabout was constructed in Paris around the Arc de Triomphe in 1901, closely followed by Columbus Circle in New York City in 1904. The first British roundabout was five years later, in Letchworth Garden City in 1909 - originally intended partly as a traffic island for pedestrians. However, the widespread use of roundabouts began when British engineers re-engineered the traffic circle in the mid-1960s to overcome its limitations of capacity and for safety issues. Unlike traffic circles, roundabouts operate with yield control to give priority to circulating traffic and eliminate much of the driver confusion associated with traffic circles and driver wait associated with junctions that have traffic lights. Roughly the same size as signalled intersections with the same capacity, roundabouts also are significantly smaller in diameter than traffic circles, separate incoming and outgoing traffic with pedestrian islands and therefore encourage slower and safer speeds (see traffic calming).

Safety

Roundabouts are safer than both traffic circles and traditional intersections—having 40% fewer vehicle collisions, 80% fewer injuries and 90% fewer serious injuries and fatalities (according to a study of a sampling of roundabouts in the United States, compared with the intersections they replaced). Roundabouts also reduce points of conflict between pedestrians and motor vehicles and are therefore considered to be safer for them. However, roundabouts, especially large fast moving ones, are unpopular with some cyclists. This problem is sometimes handled on larger roundabouts by taking foot and bicycle traffic through a series of underpasses.
At intersections with stop signs or traffic lights, the most common -- and serious -- accidents are right-angle, left-turn, or head-on collisions that can be severe because vehicles may be moving fast. Roundabouts virtually eliminate those types of crashes because vehicles all travel in the same direction.
In addition to improved vehicle and pedestrian safety, and in spite of lower speeds, roundabouts dramatically outperform traffic circles in terms of vehicle throughput and, because a roundabout's circular traffic is always moving, they outperform ordinary junctions with traffic signals as well.
Cyclists do not get the same safety benefits from roundabouts as vehicle drivers. An analysis of the national crash database in New Zealand for the period 1996-2000 shows that cyclists were involved in 26% of the reported injury crashes at roundabouts, compared to 6% at traffic signals and 13% at priority controlled intersections. Cyclists are two to three times as likely to be in a crash at a multi-lane roundabout than at a traffic signal. New Zealand researchers have proposed a design that will reduce the speed differential between cyclists and motorists, but it has design characteristics that are associated with more vehicle-vehicle crashes.
The most common roundabout crash type for cyclists involves a motor vehicle entering the roundabout and colliding with a cyclist who is already travelling around the roundabout (generally just over 50% of all cyclist/roundabout crashes fall into this category). The next most common crash type involves motorists leaving the roundabout, colliding with cyclists who are continuing further around the roundabout carriageway. Designs that have marked perimeter cycle lanes are found by research data to be even less safe than those without them.
If the adjacent cross-walks are not properly designed, there are increased risks for persons with visual impairments. This is because, unlike traffic signals, it is hard to hear if there is an adequate gap in traffic to cross. During the all-red interval at a signal, traffic comes to a stop, and blind pedestrians can tell by listening which direction gets the green light. Since there is often moving traffic at a roundabout, the sounds of non-conflicting traffic will mask gaps, or the sound of an idling vehicle whose driver has yielded to the pedestrian.
This issue has led to a conflict in the United States between the visually impaired and civil engineering communities; the visually impaired have taken the position that roundabouts (rather than signal-controlled crossings) are acceptable only if there are pedestrian crossings with lights at each road connecting to a roundabout. Engineers point out that since vehicle speeds are slower, should a driver fail to yield at a roundabout the risk and severity of pedestrian crashes are lower than if the same driver had run a red light. However, the blind community considers this to be a civil rights issue, not an engineering issue. While pedestrian crossings with traffic lights installed in roundabouts are not unheard of (see below), and would reduce the possibility that a blind pedestrian might be run over by vehicles failing to yield, they would also increase the cost of roundabout construction and maintenance substantially (essentially, both types of intersections are being built at every intersection). Furthermore, equipping a roundabout with traffic-halting lights would definitely decrease it's throughput, thereby artificially reducing or even eliminating the design's main advantage over traditional signal-equipped intersections.

Capacity

Roundabouts do not cope well with the very heavy traffic on motorways or similar roads (e.g., freeways in the U.S.), leading to long queues. Britain's strategic road network has some isolated roundabouts on otherwise almost motorway-like roads (for example, A1/A421) and even on a few motorways (for example, the A601(M), A627(M), and M271 have roundabouts on the main line). Some of these roundabouts, as well as other busy roundabouts, have had traffic lights added and are termed "signal controlled roundabouts".
A particular cause of congestion at a roundabout is when many motorists want to make a turn that crosses oncoming traffic. The two images to the right, which presume right-hand traffic, show how opposing drivers making left turns will cross 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 being 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, or even several times in order to wait for a proper opening. And, often, impatience over-rules any inclination for said driver/s to do other than 'go forward'.
On the other hand, traffic signals often suffer from inefficient operation at intersections, especially those with heavy side road traffic, or high proportions of turns across oncoming traffic. Also, quickly timed lights, or long waits at same (both 'impatience-inducing' in their own right), are factors that can-and-do exist, and regardless of traffic volume. At locations with low to medium traffic volumes, roundabouts work well under these conditions. Roundabouts actually work best when approaching volume on all legs is roughly equal (although it would be a mistake to assume that a roundabout would not work if volumes are not equal), yet roundabouts also substantially reduce delays in off-peak periods. Consider that, during off-peak travel, traffic must always stop and wait at a signal for the phase to change, even if there is no conflicting traffic. This is not the case at a roundabout - when there is low-to-no conflicting traffic in a roundabout, all vehicles safely keep moving.

Types of roundabouts

Large roundabouts such as those used at motorway intersections typically have two to four lanes around the central hub, and frequently have traffic lights regulating flow during peak hours.
Some roundabouts have a divider between traffic turning from one road onto an adjacent one, and traffic within the roundabout, enabling those making such turns to bypass the roundabout entirely. Another type of roundabout is the through-about roundabout or "hamburger" junction. This type of roundabout enables straight-through traffic on one road to cross over the central island, while all other traffic must drive around the island. As a consequence this junction must always be controlled by traffic lights. Examples of this type exist in Bracknell, Nottingham and Reading (all in England), as well as on the N2/M50 intersection in Dublin, Ireland.

Gyratory system

The term "gyratory" (for example, Hanger Lane gyratory) is sometimes used in England when a roundabout is large and has non-standard lane markings or priorities; in fact, they are more like traffic circles.

Mini roundabouts

Mini-roundabouts exist at smaller intersections to avoid the use of signals, stop signs or the necessity to yield in favour of one road of traffic. Mini-roundabouts can be a painted circle, a low dome, or often are small garden beds. Painted roundabouts and low domes can easily be driven over by most vehicles, which many motorists will do when there is no other traffic, but the practice is dangerous if other cars are present. Mini-roundabouts work in the same way as larger roundabouts in term of right of way. They can often come in "chains", making navigation of otherwise awkward junctions easier. There are usually different road signs used to distinguish mini roundabouts from larger ones.
Mini-roundabouts are also common in Irapuato, Mexico, usually marked with a tiny grassy circle enclosed edge paving, and in Calgary, Canada's inner-city Mount Royal and Rosedale neighbourhoods, where mini-roundabouts recently replaced intersections formerly controlled by stop signs to combat increasing cut-through traffic.
A slightly larger version of a mini-roundabout, sometimes called a "small roundabout", is designed with a raised centre surrounded by a sloped "overrun area" of a different colour from the roadway and up to a meter in thickness called a "truck apron". The truck apron's design discourages small vehicles from taking a shortcut over it while at the same time allowing the mini-roundabout to more easily accommodate the turning radius of larger vehicles.
In the UK the maximum diameter permissible of a mini-roundabout is 4m. Whilst it may be physically possible, it is illegal for vehicles like cars, which can turn around the mini-roundabout, to go over the painted island, or around the wrong way- vehicles should treat it like a solid island and proceed around it. (In practice, few motorists obey these rules). Some local authorities have installed double white lines around the island to indicate this, but these are not permissible. The centre island also must be able to be over-run by larger vehicles. If this is not possible, perhaps due to plants, or street furniture it is considered a small roundabout not a mini roundabout and as such must adhere to the stricter roundabout guidelines.

Raindrop or peanut shaped roundabouts

These roundabouts do not form a complete circle and are in a "raindrop" shape. They are appearing at U.S. Interstate interchanges to provide a free-flowing left turn to the on-ramps and eliminating the need for turn signals and lanes. Since the on and off-ramps are one-way, a complete circle is unnecessary. This means that drivers entering the roundabout from the bridge do not need to yield and prevents queuing on narrow, two-lane bridges. These roundabouts have been used at new interchanges so that a two-lane bridge can be built for less cost than a three-lane, as well as replacing traffic signals that are inefficient without a turning lane.

Turbo roundabouts

In the Netherlands, a relatively new type of roundabout is built increasingly often. It provides a forced spiraling flow of traffic, thus requiring motorists to choose their direction before entering the roundabout. By eliminating many conflicting paths and choices on the roundabout itself, traffic safety is increased, as well as speed, and as a result, capacity. A turbo roundabout does not allow traveling a full circle.
Several variations of the turbo roundabout exist. The basic turbo roundabout shape is designed for where a major road crosses a road with less traffic.
Turbo roundabouts are typically built with raised lane separators. Cheaper implementations with only road markings exist, but hurt the efficiency (regarding safety, speed, and capacity) of the design by enabling users to cheat the system.

Roundabouts on motorways

seealso Roundabout interchange While roundabouts do not usually interrupt motorways in the UK or Ireland, a common type of motorway intersection (suited only for lower volumes of traffic) consists of a grade separated roundabout above or below the main motorway, accessed via sliproads. Most intersections on Dublin's M50 motorway ring-road use this configuration — although several junctions have a greater volume of traffic than the capacity such roundabouts can accommodate.
In Northern Ireland the junction between the M1 and M12 (Craigavon connector motorway)is via. a standard roundabout with a raised centre, 3 onslips and 3 offslips, and 2 lanes.
An additional improvement is the 3-level stacked roundabout — this is a roundabout interchange where both roads are grade separated. In the United Kingdom, the M25/A3 and A1(M)/M18 interchanges are examples of this type. These junctions however have less capacity than a full free-flow interchange. A similar design to this is the three-level diamond interchange.
The A52 motorway in Switzerland links with three sections of road near Hinwil heading toward Hinwil, Forch and Rapperswil. The intersection takes shape in the form of a massive roundabout on the motorway. However, the sign for a roundabout is not used and a speed limit of 80 km/h (50 mph) applies. The size of the roundabout conceals the fact that it is a roundabout at all.
The A7 motorway, also in Switzerland, also has a motorway roundabout (at its terminus in Kreuzlingen), but it is smaller in size. Massachusetts Route 128, a motorway/freeway in the United States, also has two large at-grade roundabouts (or rotaries as they are called in that state) in the city of Gloucester. They are signed as Exits 10 and 11. Roundabouts in Massachusetts follow the same general rule as in the UK, with circling traffic receiving right of way.
There also was a former roundabout at the southern terminus of Route 3, a freeway linking Cape Cod to Boston; directly opposite is another freeway, the start of the Mid-Cape Highway section of US 6 heading over the Sagamore Bridge. Due to the small size of the roundabout, and the fact that Route 3 and US-6 make up the shortest way to get between the Cape and Boston, traffic tie-ups and accidents were common, especially in the summer months, when drivers from other states were often confused at how to navigate the roundabout. This roundabout was replaced with a standard freeway interchange during a three-year conversion project which concluded in 2007.
In the city of Malmö, Sweden, there is a roundabout connecting two motorways, "Autostradan" from Lund, and the "Inner ring road". It is signposted as a motorway through this roundabout. Today these two motorways are considered local, but before year 2000 they were part of the European roads E6, E20 and E22.
In the Netherlands Motorway A6 and Motorway A7 cross near Joure using a Roundabout. For the intersection between the A200 and the A9 a 3 level stacked roundabout is used. Near Eindhoven (the Leenderheide junction) the intersection for the A2 is done with a roundabout. A fly over is built for the A67 from Antwerp to Germany.

Controlled roundabouts

Some bridges on Beijing's 2nd Ring Road are controlled by traffic lights. While it may appear to defy the roundabout system at first, it works well to control the flow of traffic on the bridges, which themselves are two viaducts creating a roundabout suspended over the ring road itself.
Signal controlled roundabouts are common in Great Britain and Ireland, where they have been introduced in an attempt to alleviate traffic problems at over-capacity roundabout intersections or to prevent some flows of traffic dominating others (around the M50 in Dublin for example).

"Magic" roundabouts

The town of Swindon in Wiltshire, England is known for its "Magic Roundabout". This roundabout is at an intersection of five roads and consists of a two-way road around the central island with five mini-roundabouts where it meets the incoming roads. Traffic may proceed around the main roundabout either clockwise via the outer lanes, or anti-clockwise using the inner lanes next to the central island. At each mini-roundabout the usual clockwise flow applies.
Similar systems are found in various places in England, most famously the Moor End roundabout in Hemel Hempstead (Hertfordshire), which has six intersections; but also one in High Wycombe (Buckinghamshire)http://maps.google.co.uk/maps?ll=51.562825,-1.771449&spn=0.003068,0.00692 and the Denham Roundabout in Denham (Buckinghamshire), the Greenstead Roundabout in Colchester (Essex) and the Sadler's Farm Roundabout in Benfleet (Essex); "The Egg" in Tamworth (Staffordshire); and the Hatton Cross Roundabout in London http://maps.google.co.uk/maps?ll=51.467877,-0.423285&spn=0.003068,0.00392. Magic roundabouts are also known as "Ring Junctions", while larger ones are sometimes known as "Gyratories".

Roundabouts with trams

Tram roundabouts are most notably found in inner Melbourne, particularly in the inner suburban area of South Melbourne, where the tram network is extensive. Tram tracks always pass through the central island of these roundabouts. They can be worrying for inexperienced drivers, as they must give way, not only to vehicles coming towards them from their right, but also to trams coming at them from right-angles.
Having trams pass through small roundabouts is not a problem; through larger roundabouts it can be difficult, particularly when there is a tram junction (i.e. the tram may do more than simply pass straight through the intersection). In these cases, the roundabouts are very large, and often have tram stops in the middle. Flemington Junction is the most notorious intersection of this nature, containing a tram-stop, pedestrian crossings, three entering tram lines, traffic signals to stop vehicular traffic at each crossing point when a tram is due, service roads and pedestrian crossing.
There are a few larger roundabouts in Brussels, Belgium, where several tram routes converge from different directions, and the tram lines are laid around the roundabout allowing the trams to follow the same path as other traffic.
In Dublin, Ireland, the Red Cow ("Mad Cow") roundabout at the N7/M50 intersection is particularly infamous. It is a grade-separated motorway junction, and is signal-controlled with secondary lanes (separate from the main roundabout) for those making left turns. The junction, the busiest in Ireland, had tram lines added to it with the opening of the LUAS system in 2004. The tracks pass across one carriageway of the N7, and across the southern M50 sliproads. Trams pass at a frequency of every 5 minutes at rush hour.
In Gothenburg, Sweden the roundabout and Korsvägen tram stop (the Crossroad) at the Trade fair is of this type, and is rather infamous in the city. It is heavily trafficked by cars, and about one tram or bus per minute passes.
In Wrocław, Poland, trams pass through the Powstańców Śląskich Roundabout, having a stop in the roundabout (north-headed track).
In Kiev, Ukraine an interchange of two "fast tram" lines is done below a roundabout.
Oslo, Norway also has many roundabouts with tram tracks passing through; for example at Bislett, Frogner plass, Sinsen, Solli plass and Storo.
In Wolverhampton, England, the Midland Metro tram passes through the centre of a roundabout on approach to its terminus at St Georges. This also happens in New Addington on the Croydon Tramlink on Old Lodge Lane at the junction to King Henry's Drive. An underpass in Sheffield, England allows the tram to travel below a major roundabout, avoiding what would otherwise be a serious hindrance to traffic. A second notable tram/roundabout feature on the Sheffield system has three main branches meet and junction together atop a large, earth-worked traffic island with each line being bridged across to the outside of the feature high above the traffic, along with a couple of pre-existing walkway bridges that are now complemented by the pedestrian paths set alongside two of the incident lines.
In Salt Lake City, Utah a light rail line on the south side of the University of Utah crosses a roundabout where Guardsman Way meets South Campus Drive. Like virtually all rail crossings in the United States, both crossings in the circle are equipped with boom barriers.

Roundabouts with railways

In Jensen Beach, Florida, the main line of the Florida East Coast Railway running north-south bisects the two-lane roundabout at the intersection of Jensen Beach Boulevard running east-west and three other roads and the service entrance to a large shopping plaza. Boom barriers are in place at the railway crossings. The landscaped centre island bisected by the tracks was originally curbed, but 18-wheelers had trouble negotiating the roundabout, so the curbs were replaced with painted drive over concrete strips. A proposed fountain in the centre island has never been built. The roundabout was built in the early 2000s and has improved traffic flow considerably although there are still delays caused by the many long freight trains coming through.

Hamburger roundabout/throughabout/cut-through roundabout

These resemble a normal roundabout but are signalised and have a straight-through section of carriageway for one of the major routes. The hamburger name derives from the fact that the plan view resembles the cross-section through a hamburger. There are two such examples on the A580 East Lancashire Road in St Helens, England, one at Haydock Island in Merseyside (which also features the M6 passing overhead), the second is on the Astley/Boothstown border near to Manchester. More examples are the A6003 at Kettering and the A538 near Manchester Airport http://maps.google.co.uk/maps?f=q&hl=en&geocode=&sll=54.162434,-3.647461&sspn=9.142768,20.43457&ie=UTF8&ll=53.361757,-2.29346&spn=0.009092,0.019956&t=k&z=16&om=1. Yet another can be seen at the junction of Morley Drive and Alexander Drive in Perth, WA, Australia. An example of such an intersection in the United States can be found on the Revere Beach Parkway in Everett, Massachusetts.

Roundabouts and Cyclists

Cycle facilities at roundabouts

Research has shown that even in large circular intersections that lack modern roundabout design features, a high rate of bicycle/motor vehicle crashes occurs when bicyclists are riding around the outside. Design guidance for modern roundabouts recommends terminating cycle lanes well before the entrances, so bicyclists merge into the stream of motor traffic.
A 1992 study from the German Transport Ministry's research institute has cast particular light on this issue. The study found that bicyclists' risk is high in all such intersections, but it is much higher when the intersection has a marked bicycle lane or sidepath around its outside (see "Marked perimeter cycle lanes" below). The results of this study concerning circular intersections are summarized on the web (in German, but partially translated below). A report about accidents at four-arm roundabouts was published by the UK Transport and Road Research Laboratory (TRRL) (now TRL) in 1984.
Collisions typically occur when a motorist is entering or leaving the circular roadway. A motorist entering the circular roadway must yield to traffic in it, but such traffic will generally keep away from the outside of the circular roadway (as with a vehicle in the photo) if passing an entrance. A bicyclist close to the edge of the roadway is not in the usual position where an entering motorist expects to look for circulating traffic.
When exiting the circular roadway, a motorist must look ahead to steer, and to avoid colliding with another vehicle ahead or with pedestrians in a crosswalk. As the circular roadway curves away from the exit, the path of a vehicle exiting the circular roadway is relatively straight, and so the exiting motorist may often not need to slow substantially. However, if it is necessary to yield to a bicyclist riding around the outside, the exiting motorist must look toward the rear, to the outside of the intersection. With many vehicles, such as vans, the driver's view in this direction is obstructed. The task burden of the motorist is therefore substantially increased if bicyclists ride around the outside. The resulting conflicts, and more frequent requirements for motorists to slow or stop, also reduce the efficiency of traffic flow which is one of the major advantages of the circular intersections. Cycle lanes around the outside of circular intersections are therefore falling out of favour.

Marked perimeter cycle lanes

An early attempt to deal with the problem was to mark preferential lanes for cyclists. With cycle lanes, bicyclists do not merge into the flow of motor traffic in the roundabout, but rather, they travel around the outside, relieving them of the requirement to merge. The coloured road surface and edge lines of the cycle lanes indicate that motorists are required to yield to bicyclists at all locations where their paths may cross.

Modern design guidance

The special features of modern roundabouts, including splitter/diverter islands and small diameter of the circular roadway, decrease the speed of motor traffic and so reduce the risk of collisions for motorists as well as cyclists below that of conventional intersections. Design guidance for modern roundabouts recommends terminating cycle lanes well before the entrances, so cyclists merge into the stream of motor traffic. Cyclists who lack the confidence to do this may use the crosswalks as pedestrians. Modern design guidance also recommends placing the crosswalks far enough from the roundabout so that at least one exiting vehicle can wait without blocking the circular roadway. A roundabout with 2 lanes should place the crosswalk two car lengths from the intersection.

Examples of roundabouts

Miscellany

References

  • R. Schnüll, J. Lange, I. Fabian, M. Kölle, F. Schütte, D. Alrutz, H.W. Fechtel, J. Stellmacher-Hein, T. Brückner, H. Meyhöfer: Sicherung von Radfahrern an städtischen Knotenpunkten [Safeguarding bicyclists in Urban Intersections], Bericht der Bundesanstalt für Straßenwesen zum Forschungsprojekt 8952, 1992
  • http://bernd.sluka.de/Radfahren/Vortragsfolien.html Scroll to the section labeled "Kreisverkehr". A translation of the text reads: Graphic from Sicherung von Radfahrern an städtischen Knotenpunkten [Safeguarding bicyclists in Urban Intersections], (BASt, 1992). Accident numbers in large circular intersections with different bicycle facilities show: 1. why there should be no sidepaths or bike lanes in these intersections; 2. Even when bicyclists use the roadway, their risk is relatively high in these intersctions.
  • See for example Modern Roundabouts, an Informational Guide, http://www.tfhrc.gov/safety/00068.htm and the section on roundabouts in the US Manual on Uniform Traffic Control Devices, http://mutcd.fhwa.dot.gov/HTM/2003/part3/part3b2.htm#figure3B27 (you may have to scroll down the page).
  • Maycock, G., and Hall, R. D. (1984). "Accidents at 4-Arm Roundabouts." TRRL1120, Transport and Road Research Laboratory (TRRL), Crowthorne, England.
  • Wilke, A. and Koorey, G. (2001). How Safe are Roundabouts for Cyclists? In TranSafe Issue 5, April 2001. Wellington, NZ. http://viastrada.co.nz/sites/viastrada/files/Transafe_05.pdf PDF
  • Campbell, D., Jurisich, I., Dunn, R. 2006. Improved multi-lane roundabout designs for cyclists. Land Transport New Zealand Research Report 287. 140 pp. http://www.landtransport.govt.nz/research/reports/287.pdf PDF
  • Darr, Deanna. "Roundabout - Circular intersections may help traffic woes." Boise Weekly Online Edition, May 9 2007. Boise, Idaho http://www.boiseweekly.com/gyrobase/Content?oid=oid%3A220027

External links

gyratory in Czech: Kruhový objezd
gyratory in Danish: Rundkørsel
gyratory in German: Kreisverkehr
gyratory in Spanish: Rotonda
gyratory in Esperanto: Trafikcirklo
gyratory in Persian: فلکه
gyratory in French: Carrefour giratoire
gyratory in Indonesian: Bundaran lalu lintas
gyratory in Italian: Rotatoria
gyratory in Dutch: Rotonde
gyratory in Japanese: ラウンドアバウト
gyratory in Polish: Rondo
gyratory in Portuguese: Rotatória
gyratory in Slovenian: Krožno križišče
gyratory in Finnish: Kiertoliittymä
gyratory in Swedish: Cirkulationsplats
gyratory in Tamil: சுற்றுச்சந்தி
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