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Encyclopedia > Roundabout intersection

A roundabout, rotary, or gyratory circus is a type of road junction (or traffic calming device) at which traffic streams circularly around a central island after first yielding to the circulating traffic. In the United States it is technically called a "modern roundabout", to emphasize the distinction from the older, larger sort of traffic circle. Roundabouts are statistically safer than both traffic circles and traditional intersections, though they do not cope as well with the traffic on motorways or similar fast roads. Roundabout sign. ... In the field of road transport, a road junction is a place where two or more roads either meet or cross. ... A traffic calming measure in Germany: street narrowing Traffic calming is a set of strategies used by urban planners and traffic engineers which aims to slow down traffic and improve safety for pedestrians and bicyclists. ... Western vehicular traffic is generally organized, flowing in lanes of travel for a particular direction, with interchanges, traffic signals, or signage at intersectons to facilitate the orderly and timely flow of traffic. ... A motorway (Ireland, New Zealand, the United Kingdom and some Commonwealth nations) is both a type of road and a classification. ...

Contents

Difference between roundabouts and traffic circles

Roundabouts are sometimes referred to as traffic circles, but a technical distinction was made between roundabouts and traffic circles in the mid-1960s: Events and trends The 1960s was a turbulent decade of change around the world. ...

roundabout traffic circle
Entering vehicles yield Stop sign, stop signal, or giving priority to entering vehicles
Vehicles in the roundabout have priority over the entering vehicle Allow weaving areas to resolve conflicted movement
Use deflection to maintain low speed operation Some large circles provide straight path for higher speed
No parking is allowed Some large circles permit parking within the circle
Pedestrians (are usually) prohibited from the central island Some large circles allow pedestrians on central island
All vehicles circulate around the central island Mini-traffic circles with left-turning vehicles passing to the left¹ of the central island.
(Source for table: Oregon Department of Transportation [1] (http://www.odot.state.or.us/techserv/engineer/pdu/Roundabouts/general.htm))

1. For countries that drive on the right-hand side of the road. A roundabout, rotary, or gyratory circus is a type of road junction (or traffic calming device) at which traffic streams circularly around a central island after first yielding to the circulating traffic. ... A traffic circle is an intersection with a circular shape and, usually, a central island. ... State nickname: Beaver State Other U.S. States Capital Salem Largest city Portland Governor Ted Kulongoski Official languages None Area 255,026 km² (9th)  - Land 248,849 km²  - Water 6,177 km² (2. ...

History and safety

A diagram of movement within a roundabout in a country where traffic drives on the left

The first actual modern roundabout was constructed in New York City, United States in 1904. However, the widespread use of roundabouts began when British engineers reengineered 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 signalized 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). Representation of a UK roundabout (with cars giving way and indicating) - originally created by Mintguy, prettified by Fredrik. ... This article concerns rules of the road regarding land vehicles; for sea-going vehicles, see International Regulations for Preventing Collisions at Sea. ... Events and trends The 1960s was a turbulent decade of change around the world. ... Western vehicular traffic is generally organized, flowing in lanes of travel for a particular direction, with interchanges, traffic signals, or signage at intersectons to facilitate the orderly and timely flow of traffic. ... In the field of road transport, a road junction is a place where two or more roads either meet or cross. ... Traffic lights will sometimes differ where there are several lanes of traffic. ... A pedestrian at the intersection of Alinga Street and Northbourne Avenue, Canberra, Australia A pedestrian is a person travelling on foot, whether walking or running. ... A traffic calming measure in Germany: street narrowing Traffic calming is a set of strategies used by urban planners and traffic engineers which aims to slow down traffic and improve safety for pedestrians and bicyclists. ...


Roundabouts are safer than both traffic circles and traditional intersections—having 40% fewer vehicle collisions, 80% fewer injuries and 90% fewer serious injuries and deaths (according to a study of a sampling of roundabouts in the United States, compared with the intersections they replaced). Roundabouts also significantly reduce potential 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, and can be dangerous for, some cyclists. This problem is sometimes handled on larger roundabouts by taking foot and bicycle traffic through a series of underpasses. An underground pedestrian tunnel between buildings at MIT. Note the utility pipes running along the ceiling. ...


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 circular traffic is always moving, in roundabouts, they outperform ordinary junctions with traffic signals as well.


However, due to the fact that vehicle traffic must yield instead of stop, there are some safety concerns for bicyclists who cycle alongside the road and especially for persons with visual impairments. Safety concerns for the second group of people is especially important in countries that have legislation protecting the rights of people with disabilities. The term disability, as it is applied to humans, refers to any condition that impedes the completion of daily tasks using traditional methods. ...


This issue has led to a mutually frustrating conflict in the United States between the visually impaired and civil engineering communities; the visually impaired have taken the position that roundabouts are acceptable only if there are pedestrian crossings with lights at each road connecting to a roundabout. Although such crossings would reduce the possibility that a blind pedestrian might be run over by vehicles entering or exiting the roundabout at unsafe speeds, they would also increase the cost of a roundabout and decrease its throughput. In modern usage, civil engineering is a broad field of engineering that deals with the planning, construction, and maintenance of fixed structures as they related to earth, water, or civilization and their processes. ... Blindness can be defined physiologically as the condition of lacking sight. ...


In addition, roundabouts do not cope well with the traffic on motorways or similar roads, thus leading to long tailbacks when they are encountered by the motorist. Britain's strategic road network has many isolated roundabouts on otherwise almost motorway-like roads (for example, A1/A421) and even on 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".


Types of roundabout

There are many variations in the design 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 left (in right-hand drive countries) and other traffic, enabling those making left 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, whilst 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 and Reading, Berkshire, as well as on the N2/M50 intersection in Dublin, Ireland. Bracknell is a town of about 50,000 people (1991) in the Bracknell Forest, in the English county of Berkshire. ... St Marys Church and market Reading is a town and unitary authority in Berkshire in England. ... The N2 road is a National Primary Route in the Republic of Ireland, connecting Dublin with Derry, passing through the eastern part of Ireland. ... For the English motorway, see M50 motorway (United Kingdom) The M50 motorway is a motorway in the Republic of Ireland. ... Dublins Hapenny Bridge. ...


Mini roundabouts

Enlarge
A mini roundabout in the United Kingdom, where a painted white circle is used for the centre. The arrows show the direction of traffic flow.

Mini roundabouts exist at smaller intersections to avoid the use of signals, stopsigns or the necessity to yield in favour of one road of traffic. Mini-roundabouts can either be a painted circle or dome shaped. Painted roundabouts can be driven over; in the UK, some motorists ignore convention at times of low traffic presence and drive directly over such roundabouts as if they do not exist. Mini roundabout 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. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... See also: street sign theft External links http://homepages. ...


Roundabouts on motorways

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 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. Dublins Hapenny Bridge. ... For the English motorway, see M50 motorway (United Kingdom) The M50 motorway is a motorway in the Republic of Ireland. ...


The A52 motorway in Switzerland links with three sections of road heading toward Hinwil, Forch and Rapperswil near Hinwil. 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 A52 at the Zumikon starting point The A52 motorroad The A52 is a motorroad (German: Autostrasse) connecting Zumikon in the canton of Zürich with Hinwil and Rapperswil in the canton of St. ... Rapperswil is a small town in the canton of St. ...


The A7 motorway also has a motorway roundabout (at its terminus in Kreuzlingen), but it is smaller in size. The A7 motorway between Kreuzlingen and Grüneck (August 2004 image) The A7 is a motorway which runs from Winterthur in northeastern Switzerland through to Kreuzlingen, a border town with Konstanz (Germany). ... Kreuzlingen is a locality in Switzerland. ...


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. Beijing  listen (Chinese: 北京; pinyin: ; Wade-Giles: Pei-ching; ; Postal System Pinyin: Peking), is the capital city of the Peoples Republic of China. ... 2nd Ring Road (Eastern segment, taken in July of 2004) Yonghegong Lamasery from the 2nd Ring Road (Northern segment, taken in July of 2004) Central to Beijing, the 2nd Ring Road (pinyin: Er Huan Lu) lies just a few kilometres away from the city centre and is an extremely convenient...


Signal controlled roundabouts are relatively common in Ireland, where they have come about in an attempt to alleviate traffic problems at over-capacity roundabout intersections (around the M50 in Dublin for example). The Red Cow ("Mad Cow") roundabout at the N7 intersection is particularly infamous, being signal-controlled, having secondary lanes for those making left hand turns, and now accommodating a tram line. For the English motorway, see M50 motorway (United Kingdom) The M50 motorway is a motorway in the Republic of Ireland. ... Dublins Hapenny Bridge. ... The N7 road is a National Primary Route in the Republic of Ireland, connecting Dublin to Limerick. ... Luas (from the Irish for speed) — also promoted in the development stage as the Dublin Light Rail System — currently encompasses two unconnected on-street light rail transit systems in Dublin, Ireland. ...


"Magic" Roundabouts

The town of Swindon in Wiltshire, England is famous for its "Magic Roundabout" (not to be confused with The Magic Roundabout) which is made up of one large center roundabout and five smaller (mini) roundabouts around the center. Traffic circulates anti-clockwise around the main central roundabout, with the normal rule applying at each mini-roundabout within. Swindon is a large town of Wiltshire, England, located in the South West of the UK (between London and Bristol). ... A bridge over the river Avon at Bradford-on-Avon in Wiltshire Wiltshire (abbreviated Wilts) is a large southern English county. ... Royal motto: Dieu et mon droit (French: God and my right) Englands location within the UK Official language English de facto Capital London de facto Largest city London Area  - Total Ranked 1st UK 130,395 km² Population  - Total (2001)  - Density Ranked 1st UK 49,138,831 377/km² Religion... The Magic Roundabout in Swindon was constructed in 1972 and consists of one large roundabout containing 5 mini-roundabouts. ... Le Manège Enchanté (known in English as The Magic Roundabout) was a childrens television programme created in France in 1963 by Serge Danot. ...


Similar systems are found in various places in England, most famously the Moor End roundabout in Hemel Hempstead in Hertfordshire, which has six intersections, but also High Wycombe and Denham in Buckinghamshire, Colchester and Benfleet in Essex, Tamworth in Staffordshire and Hatton Cross in London. Magic roundabouts are also known as "Ring Junctions". The Magic Roundabout in Hemel Hempstead is the familiar name given to a complex road junction also known as the Moor End roundabout. ... Hemel Hempstead is a town in Hertfordshire, England with a population of 81,143 at the 2001 Census. ... Hertfordshire (pronounced Hartfordshire and abbreviated as Herts) is an inland county, officially part of the East of England Government region. ... See High Wycombe, Western Australia for the suburb of Perth. ... Denham is a village in Buckinghamshire, England. ... Buckinghamshire (abbreviated Bucks) is a county in south central England. ... This article is about the town in England. ... This article is about the county of Essex in England. ... This article describes Tamworth, Staffordshire in England. ... Staffordshire (abbreviated Staffs) is a landlocked county in the Midlands of England. ... Greater London and the Regions of England. ...


In addition, many British cities have ring roads consisting effectively of a magic roundabout around the city—normally a two way A-Road or Dual carriageway with roundabouts instead of intersections. A beltway (American English), ring road or orbital motorway (British English) is a circumferential highway found around many cities. ... This early German Autobahn uses a dual carriageway design. ...


The Kinsale Road Roundabout in Cork, Ireland is nicknamed "The Magic Roundabout" although not of the aforementioned type. It is in fact a very large and irregularly shaped, three lane, signal controlled roundabout. The roundabout is situated on the N25 southern ring road dual carriageway, at the intersection with a dual-carriageway to the city centre, a road to Bishopstown, and the airport or Kinsale road. With the huge traffic volumes at the intersection, the dangerous and difficult navigation of the roundabout has given rise to the "Magic Roundabout" nickname. Cork - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Market Street in Kinsale, one of the towns oldest thoroughfares Kinsale (Cionn tSáile in Irish) is a town in County Cork, Ireland. ...


The term "gyratory" (for example, the Hanger Lane Gyratory system) 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.


Note that junctions with the name "Magic Roundabout" are not necessarily of this type. For example, the Magic Roundabout at the junction of Tyndall Street and Ocean Way in Cardiff is magic in name only - it is a normal 4-way roundabout with its exits at near-right angles. Cardiff (Welsh: Caerdydd, from caer, fort, and dydd, Aulus Didius) is the capital and largest city of Wales. ...


Roundabout decorations

Roundabouts often have unique designs in the central island. These can range from flower beds, rocks, hills, statues and fountains.


External links

  • Portland, Oregon's city government page on the subject (http://www.trans.ci.portland.or.us/trafficcalming/devices/roundaboutspage.htm)
  • Reducing traffic frustration: roundabouts in North America (http://www.drivers.com/article/334/)
  • The Magic Roundabout of Swindon (http://www.swindonweb.com/life/lifemagi0.htm)
  • The BBC takes a lighthearted look at The Hanger Lane Gyratory System in London (aimed at non-native drivers) (http://www.bbc.co.uk/dna/place-london/A303346)
  • List of UK Magic Roundabouts (http://www.pberry.plus.com/ukroads/magicroundabouts/)
  • Roundabouts Canada (http://www.roundabouts.ca/)

  Results from FactBites:
 
Roundabout - Wikipedia, the free encyclopedia (1841 words)
Roundabouts are statistically safer than both traffic circles and traditional intersections, though they do not cope as well with the traffic on motorways or similar fast roads.
Roundabouts are safer than both traffic circles and traditional intersections—having 40% fewer vehicle collisions, 80% fewer injuries and 90% fewer serious injuries and deaths (according to a study of a sampling of roundabouts in the United States, compared with the intersections they replaced).
The roundabout is situated on the N25 southern ring road dual carriageway, at the intersection with a dual-carriageway to the city centre, a road to Bishopstown, and the airport or Kinsale road.
Tooele County Roundabout Design Guidelines (2423 words)
Roundabout Design Guidelines 1995 by Ourston and Doctors, was created for the State of California DOT and follows the British model for roundabout design.
The approach curve to the roundabout shall be the same radius or smaller than the radius of the curved path that a vehicle would be expected to travel through the roundabout.
On arterial roundabouts, the splitter islands shall be at least 6 feet wide to shelter a pedestrian and be a reasonable target to be seen by approaching traffic.
  More results at FactBites »

 
 

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