Wikipedia

Turnaround (road)

In the field ofroad transport,aturnaroundis a type ofjunctionthat allows traffic traveling in one direction on a road to efficiently make aU-turn(to reverse course and travel the opposite direction) typically without backing up or making dangerous maneuvers in the middle of the traffic stream. While many junction types permit U-turns, the termturnaroundoften applies to road junctions built specifically for this purpose.

Junction types designed specifically for U-turns

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The following road junction types are designed specifically to allow U-turns.

  • TheTexas U-turnallows traffic traveling on one direction of a one-wayfrontage road,running parallel to a highway, to cross the highway (via agrade separation) and turn onto the other frontage road, traveling in the opposite direction. The term refers to roadworks which are specially built for this purpose; it does not refer to use of an intersecting roadway to navigate between frontage roads.[1]
  • Themedian U-turn crossover(often called a "Michigan left" in the United States) allows traffic traveling in one direction on adivided highway(typically one withtraffic lightsandat-gradeintersections) to perform a U-turn through themedian.
  • A junction resembling a "backwardjughandle"is sometimes found, allowing U-turns. According to the U.S.Federal Highway Administration,this is actually just a variant of a standard median U-turn crossover, built to accommodate roads with medians too narrow to otherwise permit a U-turn to be made safely.[2]Traffic wishing to turn around executes a turn across oncoming traffic (left in countries where trafficdrives on the right;right in countries where traffic drives on the left) onto the at-grade ramp (sometimes called a "bulb out" or a "loon" ),[3][4]but rather than merging onto a crossing road, the "bulb out" turns back and merges onto the road the traffic just left, in the opposite direction.
  • Agrade-separatedrampcan be used to allow traffic to turn around.
    • An example on acontrolled-access highwayis the Sabine River Turnaround, exit 1 on westboundInterstate 10inCalcasieu Parish,Louisiana,United States, just before theSabine Riverand theTexasborder.[9][10]U-turn traffic exits normally onto the U-turn ramp, which forms anunderpassbelow the highway; traffic then rejoins the highway at an eastbound entrance ramp.
    • Examples on a controlled-access highway withfrontage roadsare on the Manuel Gómez Morín Beltway, just north and south of Mariano Otero Avenue inZapopan,Mexico, just outsideGuadalajara.[11][12][13][14]Here, traffic travels to a frontage road, whose inner (left) lane leads to a U-turn ramp which descends and forms an underpass below the beltway; traffic then ascends and joins the inner (left) lane of the opposing frontage road.
    • Other examples on a controlled-access highway are on theDamansara–Puchong (E11) Expressway(also known by itsMalaysianacronym,LDP), between exit 1114 (the Puchong Jaya Interchange) and exit 1118 (the Puchong Intan Interchange), inPuchong,Malaysia, nearKuala Lumpur.[15]Traffic drives on the left, and the outer (left) lanes serve as hybrid entrance or exit lanes and frontage roads. In each direction, outer-lane traffic can travel to a U-turn ramp which forms anoverpassabove the LDP. The U-turn ramps come close to each other, but remain separate; no roadway surface is shared by opposing traffic.
    • An example on anundivided highwayis on theSanibel Causeway,connectingSanibel Islandwith the mainland in South Fort Myers,Florida,United States.[16][17]Traffic traveling toward the mainland can exit onto a U-turn underpass, then return on the causeway to Sanibel Island.
  • In some countries, acul-de-sacallows a smooth turnaround at the end of a dead end street.

Junction types which permit U-turns

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The following junction types typically permit U-turns but are not designed specifically for that purpose.

  • Normalat-gradeintersectionson divided highways often allow traffic traveling on the divided highway to perform a U-turn, often when there is a green light for traffic turning onto the side road, crossing the opposing lanes (left turns in countries where trafficdrives on the right;right turns in countries where traffic drives on the left).
  • Traffic at at-grade intersections withjughandlescan usually use the jughandle ramps and side roads to turn back onto the original road in the opposite direction.
  • Traffic circlesandroundaboutsmake turning around rather easy, and usually, with the right of way.
  • Many freewayinterchangeswithsurface streetsare configured so that traffic on the freeway can exit onto the surface street, and re-enter the freeway in the opposite direction.
  • Thecloverleaf interchangepermits turning around by navigating two consecutive "leaves" of the clover pattern.

Hybrid junctions

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  • On 8 de Julio Avenue, just north of the Manuel Gómez Morín Beltway inTlaquepaque,Mexico, just outsideGuadalajara,there is a U-turn junction formed from two other types of junctions.[18][19]First, traffic wanting to turn around travels onto what theNew Jersey Department of Transportationin the United States defines as a "Type B"jughandle(one used where there is no cross street, allowing a U-turn or a turn onto a side street).[20]Then, U-turning traffic crosses the road and travels along a narrow median variant of a median U-turn crossover, completing the turn. The entire junction resembles a grade-separated turnaround ramp as described above, except this one is at-grade.

Non-junctions

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Overpass for a U-turn onThane–Belapur roadinGreater Mumbai

References

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  1. ^Purcell, Brian (November 29, 2012)."Texas Highways Primer".The Texas Highway Man Pages.Self-published.RetrievedJune 3,2013.[unreliable source?]
  2. ^Staff (August 2004)."Alternative Intersection Treatments".Signalized Intersections: Informational Guide.Federal Highway Administration.RetrievedAugust 11,2012.
  3. ^Staff."Overview".Thru Turn Intersection.Utah Department of Transportation.Archived fromthe originalon June 23, 2012.RetrievedSeptember 24,2011.
  4. ^Staff (October 2009)."Restricted Crossing U-Turn Intersection".Alternative Intersections/Interchanges: Information Report.Federal Highway Administration. FHWA-HRT-09-059.RetrievedAugust 31,2012.
  5. ^Staff."U.S. Route 101 - Lincoln Beach Parkway: Lincoln County, OR"(PDF).Flexibility in Highway Design.Federal Highway Administration.RetrievedAugust 11,2012.
  6. ^Microsoft;Nokia."US 101, Lincoln Beach, Oregon (north)"(Map).Bing Maps.Microsoft.RetrievedAugust 11,2012.
  7. ^"US 101, Lincoln Beach, Oregon"(Map).Google Maps.RetrievedAugust 11,2012.
  8. ^Microsoft; Nokia."US 101, Lincoln Beach, Oregon (south)"(Map).Bing Maps.Microsoft.RetrievedAugust 11,2012.
  9. ^"Interstate 10, exit 1, Calcasieu Parish, Louisiana"(Map).Google Maps.RetrievedAugust 18,2012.
  10. ^Microsoft; Nokia."Interstate 10, exit 1, Calcasieu Parish, Louisiana"(Map).Bing Maps.Microsoft.RetrievedAugust 18,2012.
  11. ^Microsoft; Nokia."Manuel Gómez Morín Beltway, just north of Mariano Otero Avenue, Zapopan, Jalisco, Mexico"(Map).Bing Maps.Microsoft.RetrievedAugust 18,2012.
  12. ^"Manuel Gómez Morín Beltway, just north of Mariano Otero Avenue, Zapopan, Jalisco, Mexico"(Map).Google Maps.RetrievedAugust 18,2012.
  13. ^Microsoft; Nokia."Manuel Gómez Morín Beltway, just south of Mariano Otero Avenue, Zapopan, Jalisco, Mexico"(Map).Bing Maps.Microsoft.RetrievedAugust 18,2012.
  14. ^"Manuel Gómez Morín Beltway, just south of Mariano Otero Avenue, Zapopan, Jalisco, Mexico"(Map).Google Maps.RetrievedAugust 18,2012.
  15. ^"Puchong, Malaysia (rotated & labeled Google Earth view)"(Map).Google Maps.RetrievedAugust 20,2012.
  16. ^Microsoft; Nokia."Sanibel Causeway, Florida"(Map).Bing Maps.Microsoft.RetrievedAugust 18,2012.
  17. ^"Sanibel Causeway, Florida"(Map).Google Maps.RetrievedAugust 18,2012.
  18. ^Microsoft; Nokia."Tlaquepaque, Mexico"(Map).Bing Maps.Microsoft.RetrievedAugust 20,2012.
  19. ^"Tlaquepaque, Mexico"(Map).Google Maps.RetrievedAugust 20,2012.
  20. ^"Roadway Design Manual".New Jersey Department of Transportation.December 7, 2011. Section 6. Archived fromthe originalon August 16, 2012.RetrievedAugust 20,2012.
  21. ^"Ontario Highway 11 at S. Sparrow Lake Road/Goldstein Road, Severn, Ontario, Canada"(Map).Google Maps.RetrievedAugust 31,2012.
  22. ^Microsoft; Nokia."Ontario Highway 11 at S. Sparrow Lake Road/Goldstein Road, Severn, Ontario, Canada"(Map).Bing Maps.Microsoft.RetrievedAugust 31,2012.
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