Quadrant roadway intersection explained

A quadrant roadway intersection adds an additional "quadrant roadway" between two legs of an intersection. This roadway adds two three-way intersections in addition to the original four-way intersection, moving all left turns (in right-hand traffic countries) or right turns (in left-hand traffic countries) from the main intersection. The design is intended to improve traffic flow by reducing signal timing phases from four to two in the main intersection. The design is intended for intersections where large artery routes meet in an area of dense development and high pedestrian volume.[1] [2]

Proponents also point to a reduction in places where accidents could occur from vehicles potentially crossing paths, as well as a low development cost compared to roundabouts or the more complex single-point urban interchange designs.[3] [4] Opponents point to the increase in points where accidents could occur with merging traffic as well as the non-traditional nature of the design, which has the potential to confuse drivers. Opponents also rebut low-cost claims, pointing to right-of-way and construction costs of the quadrant road.

A related structure known as a jughandle accomplishes similar traffic movement from a more compact shape.

Double-quadrant intersections

Single-quadrant intersections (pictured above) feature a single quadrant road.

A double-quadrant intersection (or two-quadrant intersection) adds a second quadrant road placed opposite another.[5] [6] [7]

Quadrant interchanges

An interchange variant of the quadrant roadway intersection links grade-separated roads, generally a faster road with denser traffic, to a less traveled, slower road, via the quadrant road. This design is referred to as a one-quadrant interchange[8] or as a single-loop intersection. This type of junction is common in Germany, where it is called a "partial at-grade intersection" .[9] A so-called two-quadrant interchange also exists, which adds a second quadrant road (although the term "two-quadrant interchange" could be applied to any grade-separated junction in which there are ramps in two quadrants).[10]

Ohashi Junction in Tokyo, Japan, is also a one-quadrant interchange connecting the elevated Shibuya Route and the underground Central Circular Route of Shuto Expressway. With circular ramps built on the southwest quadrant of two expressways, the Ohashi JCT was designed in a four-leveled manner.[11]

Notes and References

  1. Web site: Signalized Intersections: Informational Guide . Turner-Fairbank Highway Research Center. August 2004. ALTERNATIVE INTERSECTION TREATMENTS. United States Department of Transportation. 3 January 2010.
  2. News: Left turns left out of road redesign . Cooke . Jordan . Mar 24, 2009 . Cary News . 3 January 2010 . dead . https://web.archive.org/web/20090410211939/http://www.carynews.com/news/cary/story/12090.html . April 10, 2009.
  3. Web site: Moving More Cars Through the Same Space Using Unconventional Intersection Designs. Hummer. Joseph E.. May 14, 2003. NCDOT Traffic Engineering Conference. North Carolina State University. 3 January 2010.
  4. Web site: Quadrant Roadway Intersection vs. Traditional Intersection. Community Planning Assn. of Southwest Idaho. 3 January 2010.
  5. Web site: Quadrant Roadway Intersection . Alternative Intersections/Interchanges: Informational Report (AIIR) . FHWA-HRT-09-060 . . April 2010 . September 4, 2017.
  6. Web site: Intersection Concept Layout Report . PDF . High Volume Intersection Study . II . Community Planning Association of Southwest Idaho . Wilbur Smith Associates . Thompson Transportation . HDR . HDR, Inc. . Hummer . . April 21, 2008 . September 4, 2017.
  7. Web site: Chapter 2: Design Controls and Criteria . PDF . ODOT Highway Design Manual . . Nelson . . Belleque . Kent . Crossler-Laird . Rich . Gutierrez . Rodger . Henson . Christopher . Lindland . Steve . Nguyen . Lily . Polly . Dave . Warrick . Dave . 2012 . September 4, 2017.
  8. Web site: Archived copy . December 23, 2014 . dead . https://web.archive.org/web/20150412160140/http://www.ctre.iastate.edu/educweb/expressway_intersections/NCHRP%2015-30,%20Offset%20T%20Case%20Study%20revised.pdf . April 12, 2015.
  9. Institut für Straßen- und Eisenbahnwesen am KIT: Entwurf und Bau von Straßen – Teil: Straßenentwurf. (PDF; 8,44 MB) Retrieved 7 September 2013.
  10. Book: Appendix A, Detailed Green Book Review with Comments . PDF . National Cooperative Highway Research Program (NCHRP) Report 650: Median Intersection Design for Rural High-Speed Divided Highways . . Maze . T.H. . Hochstein . Joshua L. . Souleyrette . Reginald R. . Preston . Howard . Storm . Richard . 978-0-309-43543-7 . 10.17226/22958 . Project Number 15-30 . 2010 . September 12, 2017.
  11. 大橋"グリーン"ジャンクションの環境への取組み . Dealing with the Environment of Ōhashi "Green" Junction . . Highway Industry Development Organization (HIDO) . 道路行政セミナー [Road Administration Seminar] . July 19, 2013 . 58 . https://web.archive.org/web/20230214044225/https://www.hido.or.jp/14gyousei_backnumber/2013data/1307/1307oohashi_JCT.pdf . February 14, 2023 . February 14, 2023.

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