{{Short description|Freeway interchange design}} {{Hatnote|This article reflects countries that drive on the right. For countries that drive on the left, reverse right and left.}} {{Use mdy dates|date=September 2025}} [[File:Camp Creek at I-285 Aerial (50924270112).jpg|thumb|A diverging diamond at Interstate 285 and Camp Creek Parkway in East Point, Georgia<br>{{coord|33|39|23.5|N|84|29|51.5|W}}]] thumb|right|A diagram illustrating traffic movements in the interchange [[File:I-75 US 224 interchange.png|thumb|right|Plan of rejected diverging diamond interchange in Findlay, Ohio]]
A '''diverging diamond interchange''' ('''DDI'''), also called a '''double crossover diamond interchange''' ('''DCD'''),<ref>{{cite web |url = https://www.fhwa.dot.gov/publications/research/safety/09054/index.cfm |title = Double Crossover Diamond Interchange |id = FHWA-HRT-09-054 |last1 = Hughes |first1 = Warren |last2 = Jagannathan |first2 = Ram |publisher = Federal Highway Administration |date = October 2009 |access-date = April 22, 2012 }}</ref><ref name=":0">{{cite web |url = https://library.modot.mo.gov/rdt/reports/unnumbrd/or10021rpt.pdf |archive-url = https://web.archive.org/web/20100530124703/https://library.modot.mo.gov/rdt/reports/unnumbrd/or10021rpt.pdf |archive-date = May 30, 2010 |url-status = dead |title = Missouri's Experience with a Diverging Diamond Interchange |date = May 2010 |page = 4 |publisher = Missouri Department of Transportation }}</ref> is a subset of diamond interchange in which the opposing directions of travel on the non-freeway road cross each other on either side of the interchange so that traffic crossing the freeway on the overpass or underpass is operating on the opposite driving side from that which is customary for the jurisdiction.<ref name=":0"/> The crossovers may employ one-side overpasses or be at-grade and controlled by traffic lights.
The diverging diamond interchange has advantages in both efficiency and safety and was cited by ''Popular Science'' as one of the best engineering innovations of 2009,<ref>{{cite journal |url = http://www.popsci.com/node/42027 |title = Gallery: Looking Back at the 100 Best Innovations of 2009 |journal = Popular Science |access-date = January 20, 2012 |archive-date = June 15, 2013 |archive-url = https://web.archive.org/web/20130615122328/http://www.popsci.com/node/42027 |url-status = dead }}</ref> despite having been sparsely used in its contemporary form in France as early as the 1970s.<ref name=Virginia-Versailles>{{cite web |author = Staff |publisher = Virginia Department of Transportation |url = http://www.virginiadot.org/projects/culpeper/zioncrossroads.asp |title = I-64 Interchange at Route 15, Zion Crossroads |date = June 13, 2013 |access-date = December 11, 2013 |archive-url = https://web.archive.org/web/20131127125317/http://www.virginiadot.org/projects/culpeper/zioncrossroads.asp |archive-date = November 27, 2013 |url-status = dead }}</ref> It has been promoted in the U.S. as part of the Federal Highway Administration's Every Day Counts initiative.<ref>{{cite book |first1 = Bastian |last1 = Schroeder |first2 = Chris |last2 = Cunningham |first3 = Brian |last3 = Ray |first4 = Andy |last4 = Daleiden |first5 = Pete |last5 = Jenior |first6 = Julia |last6 = Knudsen |date = August 2014 |title = Diverging Diamond Interchange Informational Guide |url = https://rosap.ntl.bts.gov/view/dot/29474 |location = Washington, DC |publisher = Federal Highway Administration Office of Safety |id = Publication FHWA-SA-14-067 }}</ref> The flow through a diverging diamond interchange using overpasses at the crossovers is limited only by weaving, and the flow through an implementation using traffic lights is subject to only two clearance intervals (the time during which all lights are red so that the intersection may fully clear) per cycle.<ref>{{cite web |url = http://www.ohm-advisors.com/ddi/index.cfm |title = Diverging Diamond Interchange |publisher = OHM Advisors |access-date = November 6, 2008 |archive-url = https://web.archive.org/web/20090219121255/http://www.ohm-advisors.com/ddi/index.cfm |archive-date = February 19, 2009 |url-status = dead }}</ref><ref>Gilbert Chlewicki: [https://divergingdiamond.com/history/ About History]</ref>
The greatest safety concern of the interchange stems from its relative rarity, as drivers instinctively trying to stay on the customary side of the road could use the crossover intersections to turn against the posted direction of travel. This is a rare occurrence; it is possible only when traffic is so sparse that no cars from the oncoming direction are stopped at the light, and clear signage further reduces the likelihood of such errors. {{citation needed|date=July 2025}}
== History == [[File:Interstate 44 and Route 13 diverging diamond interchange.png|upright=1.6|thumb|Pictures from the first diverging diamond interchange in the United States, in Springfield, Missouri<br />Top left: Traffic enters the interchange along Missouri Route 13<br />Top right: Traffic crosses over to the left side of the road<br />Bottom left: Traffic crosses over Interstate 44<br />Bottom right:Traffic crosses back over to the right side of the road.]] [[File:Diverging Diamond Interchange.webm|thumb|Lunchtime traffic at the diverging diamond interchange at the James River Freeway and Route 13 in Springfield]]
The first known diverging diamond interchanges were built in France during the 1970s, in the communities of Versailles (A13 at D182), Nogent-sur-Marne (A4 at N486) and Seclin (A1 at D549; featuring an asymmetrical 2/4 lane layout).<ref name=Virginia-Versailles/> The Nogent-sur-Marne interchange originally was a contraflow left interchange, then reorganized as a diverging diamond interchange in the 1980-90s, and has been completely rebuilt with a more standard layout in 2019; the other two continue to function as diverging diamond interchanges. A three-way derivative which may be considered a related precursor was also built in the UK on the M1 in 1969 to provide access to London Gateway services (formerly Scratchwood Services).
In the United States, invention of the diverging diamond interchange is credited to Gilbert Chlewicki.<ref name="Rose">{{cite news |url = https://www.npr.org/2024/05/28/nx-s1-4876879/the-diverging-diamond-interchange-may-come-soon-to-a-busy-intersection-near-you |title = The 'diverging diamond interchange' may come soon to a busy intersection near you |date = May 28, 2024 |publisher = NPR |author = Joel Rose }}</ref> In 2005, the Ohio Department of Transportation (ODOT) considered reconfiguring the existing interchange on Interstate 75 at U.S. Route 224 and State Route 15 west of Findlay as a diverging diamond interchange to improve traffic flow. Had it been constructed, it would have been the first DDI in the United States.<ref>{{cite news |last = Patch |first = David |title = French Connection May Control Traffic Flow |url = http://www.toledoblade.com/frontpage/2005/05/02/French-connection-may-control-traffic-flow.html |newspaper = The Blade |location = Toledo, Ohio |date = May 2, 2005 |access-date = April 8, 2014 }}</ref> By 2006, ODOT had reconsidered, instead adding lanes to the existing overpass.<ref>{{cite news |last = Sedensky |first = Matt |title = Missouri Drivers May Go to the Left |url = https://news.google.com/newspapers?nid=1454&dat=20060330&id=ihFPAAAAIBAJ&pg=6999,3868451 |agency = Associated Press |newspaper = Star-News |location = Wilmington, North Carolina |date = March 30, 2006 |access-date = April 8, 2014 }}</ref><ref>{{cite news |url = http://www.landlinemag.com/Story.aspx?StoryId=10845 |title = Wrong Way? Not in Kansas City |magazine = Land Line Magazine |date = March 31, 2006 |access-date = April 8, 2014 |archive-date = September 28, 2018 |archive-url = https://web.archive.org/web/20180928114827/http://www.landlinemag.com/Story.aspx?StoryId=10845 |url-status = dead }}</ref>
thumb|Southbound approach to the I-44/Route 13 interchange in Springfield
The Missouri Department of Transportation (MoDOT) was the first US agency to construct one, in Springfield at the junction between I-44 and Missouri Route 13 (at {{Coord|37.2503|-93.3107|name=Springfield, Missouri diverging diamond interchange|display=inline|scale:3000_type:landmark_region:US-MO}}). Construction began the week of January 12, 2009, and the interchange opened on June 21, 2009.<ref>{{cite web |url = http://www.modot.org/springfield/major_projects/Greene/I-44andRoute13.html |title = I-44/Route 13 Interchange Reconstruction: Diverging Diamond Design |date = April 2009 |access-date = May 19, 2009 |publisher = Missouri Department of Transportation |archive-url = https://web.archive.org/web/20110607123620/http://www.modot.org/springfield/major_projects/Greene/I-44andRoute13.html |archive-date = June 7, 2011 }}</ref><ref>{{cite press release |author = Springfield District Office |title = Public Meeting Tuesday, June 24, On I-44/Route 13 Reconstruction To Reduce Congestion, Improve Safety |publisher = Missouri Department of Transportation |date = June 19, 2008 |url = http://www.modot.org/springfield/news_and_information/District8News.shtml?action=displaySSI&newsId=19484 |access-date = June 19, 2008 }}</ref> This interchange was a conversion of an existing standard diamond interchange, and used the existing bridge.<ref>{{Cite journal |last1 = Khan |first1 = Tahmina |last2 = Anderson |first2 = Michael |date = March 2016 |title = Evaluating the Application of Diverging Diamond Interchange in Athens, Alabama |url = http://www.ijtte.com/uploads/2016-03-08/935be804-aeae-25eaIJTTE_Vol%206(1)_4.pdf |archive-url = https://web.archive.org/web/20191209163854/http://www.ijtte.com/uploads/2016-03-08/935be804-aeae-25eaIJTTE_Vol%206(1)_4.pdf |archive-date = December 9, 2019 |url-status = live |journal = International Journal for Traffic and Transport Engineering |volume = 6 |issue = 1 |pages = 38–50 |doi = 10.7708/ijtte.2016.6(1).04 |access-date = May 28, 2024 }}</ref> MoDOT reports that traffic congestion for left turns at the intersection cleared up immediately, and crashes dropped by 40–50%.<ref name="Rose" />
In 2010, the Federal Highway Administration released a publication titled "Alternative Intersections/Interchanges: Informational Report (AIIR)"<ref name="Alternative Intersections/Interchanges: Informational Report (AIIR)">{{cite report |first1 = Warren |last1 = Hughes |first2 = Ram |last2 = Jagannathan |first3 = Dibu |last3 = Sengupta |first4 = Joe |last4 = Hummer |name-list-style = amp |date = April 2010 |url = https://www.fhwa.dot.gov/publications/research/safety/09060/ |title = Alternative Intersections/Interchanges: Informational Report (AIIR) |publisher = Federal Highway Administration }}</ref> with a chapter dedicated to this design. Additional research was conducted by a partnership of the Virginia Polytechnic Institute and State University and the Turner-Fairbank Highway Research Center and published by Ohio Section of the Institute of Transportation Engineers.<ref>{{cite web |url = http://www.ohioite.org/DDI-Paper-Veh-Ped-Oper.pdf |title = Diverging Diamond Interchange and Double Crossover Intersection: Vehicle and Pedestrian Performance |first1 = Praveen K. |last1 = Edara |first2 = Joe G. |last2 = Bared |first3 = Ramanujan |last3 = Jagannathan |name-list-style = amp }}</ref>
On August 14, 2011, the Kentucky Transportation Cabinet (KYTC) completed conversion of the intersection of U.S. Route 68 and Kentucky Route 4 in Lexington to a diverging diamond design, the first in the state and the sixth completed nationally.<ref name="DDI Openings by Date">{{Cite web |title = DDI Openings by Date |url = https://divergingdiamond.com/ddi-openings-by-date/ |access-date = February 19, 2023 |website = Diverging Diamond Interchange |language = en-US }}</ref> Stantec, the engineers who completed the upgrades to the interchange, noted the solution while providing substantial cost savings over other possible options also has decreased accidents by 45 percent, improved traffic flow to more than 35,000 vehicles per day, and incorporated KYTC's goal to provide new paths for bicycles and pedestrians through the area.<ref>{{Cite web |title = US 68 (Harrodsburg Road) Widening |url = https://www.stantec.com/en/projects/united-states-projects/u/us-68-harrodsburg-road-widening |access-date = February 19, 2023 |publisher = Stantec |language = en }}{{self-published inline|date=February 2023}}</ref> That same day in Highland, Utah the seventh U.S. diverging diamond interchange opened at the intersection of I-15 and Timpanogos Highway.<ref name="DDI Openings by Date"/> According to the U.S. Department of Transportation the goals of this intersection upgrade were similar, increasing traffic capacity and improved pedestrian and bicycle access while reaching these goals without requiring substantial revisions to the existing interstate overpass. Quoting a June 2014 USDOT publication, "the DDI has made travel more efficient and accessible for all users."<ref>{{Cite web |date = June 1, 2014 |publisher = United States Federal Highway Administration |author = Office of Safety |title = Diverging Diamond Interchange: Interstate 15 and Timpanogos Highway, Lehi, UT |url = https://rosap.ntl.bts.gov/view/dot/49377 |language = English }}</ref>
The year 2016 saw the introduction of diverging diamond interchanges by three states. In February, the Oregon Department of Transportation opened one in Phoenix.<ref>{{cite web |url = https://www.fhwa.dot.gov/ipd/project_profiles/or_i5_fern_valley_interchange.aspx |website = Project Profile: I-5 Fern Valley Interchange |publisher = Federal Highway Administration |access-date = March 1, 2023 |title = FHWA - Center for Innovative Finance Support - Project Profiles }}</ref><ref>{{cite web |url = https://divergingdiamond.com/ddi-openings-by-date/ |website = Diverging Diamond Interchange |publisher = Advanced Transportation Solutions (ATS) America |access-date = March 1, 2023 |title = DDI Openings by Date }}</ref> In October, the New Mexico Department of Transportation converted the crossing of NM 14 (Cerrillos Road) and Interstate 25 in Santa Fe.<ref>{{Cite web |date = October 31, 2016 |title = Unique I-25 interchange now open for Santa Fe drivers |url = https://www.krqe.com/news/unique-i-25-interchange-now-open-for-santa-fe-drivers/ |access-date = June 14, 2022 |website = KRQE NEWS 13 - Breaking News, Albuquerque News, New Mexico News, Weather, and Videos |language = en-US }}</ref> In November, the Delaware Department of Transportation completed the conversion of the DE-1 and DE-72 (Wrangle Hill Rd) overpass west of Delaware City.<ref name=":3">{{Cite web |title = Delaware Department of Transportation - SR 72/SR 1 Diverging Diamond Interchange |url = https://deldot.gov/information/projects/SR72-SR1/index.shtml |access-date = June 29, 2020 |website = deldot.gov |language = en }}</ref><ref>{{Cite web |title = DelDOT Interactive Maps |url = https://deldot.gov/map/index.shtml?tab=TrafficCameras |access-date = June 29, 2020 |website = Delaware Department of Transportation |language = en }}</ref>
The first interchange in Canada opened on August 13, 2017, at Macleod Trail and 162 Avenue South in Calgary, Alberta<ref>{{cite news|url=https://globalnews.ca/news/3667111/canadas-first-diverging-diamond-interchange-now-open-to-calgary-traffic/|title=Canada's first 'diverging diamond interchange' now open to Calgary traffic - Calgary {{!}} Globalnews.ca|date=August 14, 2017|website=globalnews.ca|last=Yourex-West|first= Heather|language=en|access-date=March 7, 2019}}</ref> followed by one east of Regina, Saskatchewan the next year as part of the Regina Bypass project.<ref>{{Cite web |url = https://www.cbc.ca/news/canada/saskatchewan/diverging-diamond-opens-1.4569583 |title = Saskatchewan's First DDI }}</ref>
In the 2010s MoDOT designed a hybrid of a diverging diamond interchange and a roundabout that they call a "{{vanchor|Divergabout|text=divergabout}}".<ref>{{cite magazine|title=Innovations Help States Deliver Outstanding Transportation Projects|url=https://www.fhwa.dot.gov/innovation/innovator/issue75/page_05.html|magazine=Innovator|volume=13|issue=75|page=5|date=November–December 2019|publisher=Federal Highway Administration|access-date=October 11, 2025}}</ref><ref>{{cite web|author=Transporatation Planning|title=Divergabout|url=https://www.modot.org/sites/default/files/documents/Divergabout_KC.pdf|publisher=Missouri Department of Transportation|date=April 2019|access-date=October 11, 2025}}</ref> The first opened at Interstate 49/U.S. Route 71 and 155th Street where Belton meets Grandview and Kansas City on December 15, 2017,<ref>{{cite press release|author=Staff|title=City of Belton Joins MoDOT for 155th Street Interchange Ribbon Cutting|url=https://www.belton.org/edo/News/News-Updates/City-of-Belton-Joins-MoDOT-for-155th-Street-Interchange-Ribbon-Cutting|publisher=City of Belton, Missouri|date=December 15, 2017|access-date=October 11, 2025}}</ref><ref>{{Cite web |title=I-49 and 155th |url=http://www.modot.org/kansascity/major_projects/I-49_155th_Interchange.htm |url-status=dead |archive-url=https://web.archive.org/web/20171222052908/http://www.modot.org/kansascity/major_projects/I-49_155th_Interchange.htm |archive-date=December 22, 2017 |publisher = Missouri Department of Transportation }}</ref> with a second following on May 11, 2018, in nearby Lee's Summit at U.S. Route 50 and Missouri Route 291/Jefferson Street.<ref>{{cite news|first1=Cat|last1=Reid|first2=Charlie|last2=Keegan|title=New 'divergabout' opens in Lee's Summit|url=https://www.kshb.com/news/region-missouri/lees-summit/new-divergabout-set-to-open-in-lees-summit|publisher=KSHB-TV|date=May 10, 2018|access-date=October 11, 2025}}</ref>
The first diverging diamond interchange in Australia opened to traffic by the Queensland Department of Transport and Main Roads on November 28, 2019. The interchange, located in Caloundra, Queensland, connects Caloundra Road to the Bruce Highway. The former interchange was upgraded and converted as part of the larger Bruce Highway Upgrade Program.<ref>{{Cite web |title = Bruce Highway Upgrade Caloundra Road to Sunshine Motorway |url = https://sc-tmrwcmgr-cd.azurewebsites.net/projects/bruce-highway-caloundra-road-to-sunshine-motorway |access-date = August 29, 2021 |website = sc-tmrwcmgr-cd.azurewebsites.net |language = en }}</ref><ref>{{Cite web |last = Jones |first = Lauren |date = December 1, 2019 |title = Major contractor opens Australian first Diverging Diamond Interchange |url = https://roadsonline.com.au/major-contractor-opens-australian-first-diverging-diamond-interchange/ |access-date = August 29, 2021 |website = Roads & Infrastructure Magazine |language = en-US }}</ref>
In December 2019, the Virginia Department of Transportation completed the conversion of the interchange at Courthouse Road and I-95 in Stafford, VA into a diverging diamond interchange.<ref>{{Cite web |title = This New, Trippy Interchange Will Have You Driving On The Wrong Side Of The Road In Virginia |url = https://dcist.com/story/19/12/05/this-new-trippy-interchange-will-have-you-driving-on-the-wrong-side-of-the-road-in-virginia/ |access-date = December 6, 2019 |website = DCist |language = en |archive-date = December 6, 2019 |archive-url = https://web.archive.org/web/20191206160627/https://dcist.com/story/19/12/05/this-new-trippy-interchange-will-have-you-driving-on-the-wrong-side-of-the-road-in-virginia/ |url-status = live }}</ref>
In 2020, the California Department of Transportation (Caltrans) completed the first diverging diamond interchange in California. An interchange at State Route 120 and Union Road in Manteca, California was converted to this interchange and opened to traffic on November 25.<ref>{{Cite web |title = SR 120 @ Union Road |url = https://divergingdiamond.com/item/sr-120-union-road/ |access-date = May 31, 2021 |website = Diverging Diamond Interchange |language = en-US }}</ref><ref>{{Cite web |title = California's first diverging diamond interchange just debuted in Manteca |url = https://www.abc10.com/article/news/local/manteca/manteca-diverging-diamond/103-b1ba2174-cbb7-451e-a0d0-06e8e0fe8be5 |access-date = May 31, 2021 |website = abc10.com |date = November 20, 2020 |language = en-US }}</ref>
== Use == === Operational === [[File:Diverging diamond interchange, Ontario.jpg|thumb|Diverging diamond interchange on Queen Elizabeth Way in Niagara-on-the-Lake, Ontario, Canada]]
{{As of|2022|10|14|df=US}}, over 170 DDIs were operational across the world including: <!-- sort alphabetically --> * Two in Australia, with more planned <ref>{{Cite web |title = Burleigh Diverging Diamond Interchange |url = https://bgeeng.com/projects/burleigh-diverging-diamond-interchange/ |access-date = September 28, 2022 |website = BG&E |language = en-AU }}</ref><ref>{{Cite web |title = Gympie Arterial Road and Strathpine Road (Bald Hills), improve intersection |url = https://sc-tmrwcmgr-cd.azurewebsites.net/projects/gympie-arterial-road-and-strathpine-road-bald-hills-improve-intersection |access-date = November 22, 2022 |website = sc-tmrwcmgr-cd.azurewebsites.net |language = en }}{{Dead link|date=October 2025 |bot=InternetArchiveBot }}</ref> * 1 in Belgium<ref>{{Cite web |last1 = Coopman |first1 = Bart |last2 = Baert |first2 = Kate |date = October 14, 2022 |title = Goed nieuws voor de mobiliteit rond Waregem: "De Vlecht" aan het afrittencomplex is geopend |url = https://www.focus-wtv.be/nieuws/goed-nieuws-voor-de-mobiliteit-rond-waregem-de-vlecht-aan-het-afrittencomplex-geopend |url-status = live |archive-url = https://web.archive.org/web/20221014213854/https://www.focus-wtv.be/nieuws/goed-nieuws-voor-de-mobiliteit-rond-waregem-de-vlecht-aan-het-afrittencomplex-geopend |archive-date = October 14, 2022 |access-date = October 14, 2022 |website = Focus-WTV |language = nl }}</ref> * 3 in Canada<ref>{{Cite web |date = September 25, 2022 |title = Ontario's first diverging diamond interchange opens. Here's how it works |url = https://www.ctvnews.ca/toronto/ontario-s-first-diverging-diamond-interchange-opens-tomorrow-1.6083490?cache=eqlkpruxkingcp }}</ref> * 1 in Denmark, opened September 17, 2017<ref>{{Cite web |url = https://vejdirektoratet.dk/nyhed/ministeren-markerede-ibrugtagning-af-det-dynamiske-ruderanlaeg |title = Ministeren markerede ibrugtagning af det dynamiske ruderanlæg |website = Vejdirektoratet }}</ref> * 2 in France, built in 1970s * 8 in Malaysia * 2 in Saudi Arabia * 2 in South Africa * 1 in the United Arab Emirates * 1 in Costa Rica * >150 in the United States, with ~80 more under construction<ref>{{Cite web |title = Diverging diamond interchange |url = https://wsdot.wa.gov/travel/traffic-safety-methods/diverging-diamond-interchange |access-date = September 27, 2022 |website = Washington State Department of Transportation }}</ref> * 1 in Turkey<ref>{{Cite web |last=Belediyesi |first=Kocaeli Büyükşehir |title=Kaşkaldere Kavşağı'na her yönüyle tam not |url=https://www.kocaeli.bel.tr/haber/kaskaldere-kavsagina-her-yonuyle-tam-not-47065.html |access-date=2025-10-27 |website=Kocaeli Büyükşehir Belediyesi |language=tr}}</ref>
== Advantages == Compared to a diamond interchange, the advantages of a diverging diamond interchange are: * Two-phase signals with short cycle lengths, significantly reducing delay.<ref name=":2">{{cite web |url = https://library.modot.mo.gov/rdt/reports/unnumbrd/or10021rpt.pdf |archive-url = https://web.archive.org/web/20100530124703/https://library.modot.mo.gov/rdt/reports/unnumbrd/or10021rpt.pdf |archive-date = May 30, 2010 |url-status = dead |title = Missouri's Experience with a Diverging Diamond Interchange |website = www.modot.org |date = May 2010 |page = 5 }}</ref> * Reduced horizontal curvature reduces the risk of off-road crashes.{{cn|date=May 2024}} * Increases the capacity of turning movements to and from the ramps.{{cn|date=May 2024}} * Potentially reduces the number of lanes on the crossroad, minimizing space consumption.{{cn|date=May 2024}} * Reduces the number of conflict points, thus theoretically improving safety.<ref name=":0"/><ref name=advantages/> * Increases the capacity<ref name=advantages/> by removing the need for turn lanes.{{cn|date=May 2024}} * Can cost significantly less than a traditional diamond interchange.<ref name=advantages>{{cite web |title = Diverging Diamond Interchange |url = https://safety.fhwa.dot.gov/intersection/crossover/fhwasa14039.pdf |archive-url = https://web.archive.org/web/20210318114216/https://safety.fhwa.dot.gov/intersection/crossover/fhwasa14039.pdf |url-status = dead |archive-date = March 18, 2021 |access-date = June 7, 2020 }}</ref>
== Disadvantages ==
* Drivers may not be familiar with configuration, particularly with regard to merging maneuvers along the opposite side of the roadway or the crossover flow of traffic.<ref name=":1">{{cite web |url = https://library.modot.mo.gov/rdt/reports/unnumbrd/or10021rpt.pdf |archive-url = https://web.archive.org/web/20100530124703/https://library.modot.mo.gov/rdt/reports/unnumbrd/or10021rpt.pdf |archive-date = May 30, 2010 |url-status = dead |title = Missouri's Experience with a Diverging Diamond Interchange |website = www.modot.org |date = May 2010 |page = 6 }}</ref> * Pedestrian (and other sidewalk-user) access requires at least four crosswalks (two to cross the two signalized lane crossover intersections, while two more cross the local road at each end of the interchange).<ref>{{cite web |url = http://www.theatlanticcities.com/design/2011/11/diverging-diamond-interchange-abomination/453/ |title = The 'Diverging Diamond' Interchange Is an Abomination - Sarah Goodyear |publisher = The Atlantic Cities |date = September 20, 2011 |access-date = April 22, 2014 |archive-url = https://web.archive.org/web/20111113063247/http://www.theatlanticcities.com/design/2011/11/diverging-diamond-interchange-abomination/453/ |archive-date = November 13, 2011 |url-status = dead }}</ref><ref name=":1"/> This could be mitigated by signalizing all movements without impacting the two-phase nature of the interchange’s signals. * Free-flowing traffic in both directions on the non-freeway road is impossible as the signals cannot be green for both directions simultaneously. * Highway bus stops must be sited outside the interchange.{{cn|date=May 2024}} * Allowing exiting traffic to re-enter the through road in the same direction requires leaving the interchange on the local road and turning around, e.g., via a median U-turn crossover. This affects several use cases:<ref name=":1"/> ** Drivers who take the wrong exit ** Bypassing a crash at the bridge ** Allowing an oversize load to bypass a low bridge * Some factors make turning left onto a diverging diamond interchange from the highway ramp more hazardous: 1) There is a yield sign instead of a traffic light. 2) The driver can not see if the light for the through traffic is red or green. 3) The visible distance to see the oncoming through traffic from that vantage is very short. All of these combined results in the driver entering a potentially very busy interchange without sufficient information.{{cn|date=October 2025}}
== Further considerations == {{unreferenced section|date=May 2024}} * No standards currently exist for this design. * The design depends on site-specific conditions. * Additional signage, lighting, and pavement markings are needed beyond the levels for a standard diamond interchange. * Local road should be a low-speed facility, preferably under {{convert|45|mph|abbr=on}} posted speed on the crossroad approach. However, this may be mitigated by utilizing a higher design speed for the crossing movements.
== Double crossover merging interchange == thumb|3D computer generated DCMI thumb|DCMI traffic flow patterns
A free-flowing interchange variant, patented in 2015,<ref>{{cite web |url = http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8950970.PN.&OS=PN/8950970&RS=PN/8950970 |title = United States Patent 8,950,970: Double Crossover Merging Interchange |date = February 10, 2015 |publisher = United States Patent and Trademark Office |access-date = October 4, 2016 |archive-date = January 3, 2017 |archive-url = https://web.archive.org/web/20170103052803/http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8950970.PN.&OS=PN/8950970&RS=PN/8950970 |url-status = dead }}</ref> has received recent attention.<ref>{{cite web |title = TRAFFIC ENGINEERING COUNCIL BEST PAPER and BEST PRODUCT AWARD: Past Recipients |url = http://library.ite.org/pub/e1bef57d-2354-d714-5123-1a43721b5923 |publisher = Institute of Transportation Engineers |access-date = October 4, 2016 |archive-url = https://web.archive.org/web/20161004170603/http://library.ite.org/pub/e1bef57d-2354-d714-5123-1a43721b5923 |archive-date = October 4, 2016 |date = 2016 |url-status = dead }}</ref><ref>{{cite web |title = Alternative Intersections & Interchanges Symposium |url = http://onlinepubs.trb.org/onlinepubs/Conferences/2014/Intersections/program.pdf |publisher = Transportation Research Board |access-date = October 4, 2016 |archive-url = https://web.archive.org/web/20160305010501/http://onlinepubs.trb.org/onlinepubs/Conferences/2014/Intersections/program.pdf |archive-date = March 5, 2016 |date = July 21, 2014 |url-status = dead }}</ref><ref>{{cite web |last1 = Buteliauskas |first1 = Stanislovas |last2 = Juozapavičius |first2 = Aušrius |title = Interchange of a New Generation Pinavia |url = http://teachamerica.com/ai14/ai14papers/ai14_3CJuozapavicius.pdf |publisher = Military Academy of Lithuania |access-date = October 4, 2016 |archive-url = https://web.archive.org/web/20161004170852/http://teachamerica.com/ai14/ai14papers/ai14_3CJuozapavicius.pdf |archive-date = October 4, 2016 |date = June 15, 2014 |url-status = dead }}</ref> Called the '''double crossover merging interchange''' ('''DCMI'''), it includes elements from the diverging diamond interchange, the tight diamond interchange, and the stack interchange. It eliminates the disadvantages of weaving and of merging into the outside lane from which the standard DDI variation suffers. A highway U-turn requires weaving, however.
A partial DCMI has existed at the I-45/SH 6/SH 146 interchange in Bayou Vista, Texas, since at least 1969.<ref>{{cite map |author = United States Army Corps of Engineers |author2 = United States Geological Survey |year = 1969 |url = https://texashistory.unt.edu/ark:/67531/metapth453896/ |title = Virginia Point Quadrangle |type = Topographic map |series = 7.5 Minute Series |scale = 1:24,000 |location = Washington, DC |publisher = United States Geological Survey |access-date = September 6, 2025 |via = University of North Texas Libraries }}</ref> As of 2025, however, construction is underway to replace the DCMI as part of a widening project on I-45.<ref>{{cite map |author = Houston District |date = February 6, 2018 |title = I-45 at Texas City Wye |sheet = 5 |url = https://www.ci.la-marque.tx.us/DocumentCenter/View/1481/5_I-45-Texas-City-Wye-PDF |scale = Scale not given |publisher = Texas Department of Transportation |access-date = September 6, 2025 |via = City of La Marque, Texas }}</ref>
==Three-level diverging diamond interchange== Another variation of the diverging diamond was developed by the Arizona Department of Transportation (ADOT) as part of their I-10 widening/SR 210 extension project near Tucson, Arizona. The interchange (I-10 exit 270 at Kolb Road) will be reconfigured as a combination of both a diverging diamond and a three-level diamond interchange. The ramps (the top level/Kolb Road) would carry thru traffic while the diverging diamond (the second level/interchange) would be for traffic getting on or off the freeway (the third level/I-10).<ref>{{cite web |title=Interstate 10 and State Route 210 Study {{!}} Department of Transportation |url=https://azdot.gov/planning/transportation-studies/interstate-10-and-state-route-210-study |website=azdot.gov |access-date=September 7, 2023}}</ref>
== See also == * Hook turn * Jughandle * List of road interchanges in the United States * Michigan left * Single-point urban interchange (SPUI) * Superstreet
{{-}} == References == {{reflist|colwidth=30em}}
== Further reading == {{refbegin}} * {{cite web |last = Chlewicki |first = Gilbert |year = 2003 |url = http://www.urbanstreet.info/2nd_sym_proceedings/Volume%202/Chlewicki.pdf |archive-url = https://wayback.archive-it.org/all/20111020071633/http://www.urbanstreet.info/2nd_sym_proceedings/Volume%202/Chlewicki.pdf |url-status = dead |archive-date = October 20, 2011 |title = New Interchange and Intersection Designs: The Synchronized Split-Phasing Intersection and the Diverging Diamond Interchange |access-date = October 20, 2009 }} * {{cite web |last = Chlewicki |first = Gilbert |date = December 4, 2011 |url = http://www.divergingdiamond.com/about.html |title = About Chlewicki |work = The Diverging Diamond Interchange Website |access-date = January 20, 2012 }} * {{cite web |author = Innovations Library |date = May 2010 |url = http://library.modot.mo.gov/RDT/reports/UnNumbrd/or10021.pdf |title = Missouri's Experience with a Diverging Diamond Interchange: Lessons Learned |publisher = Missouri Department of Transportation }} * {{cite web |author = Turner-Fairbank Highway Research Center |url = http://www.tfhrc.gov/safety/pubs/07048/ |title = Drivers' Evaluation of the Diverging Diamond Interchange |id = FHWA-HRT-07-048 |publisher = Federal Highway Administration }} {{refend}}
== External links == {{Commons category|Diverging diamond interchanges}} * [http://www.udot.utah.gov/main/uconowner.gf?n=14769524027177477 DDI Guideline – A UDOT Guide to Diverging Diamond Interchanges] {{Webarchive|url=https://web.archive.org/web/20140814220027/http://www.udot.utah.gov/main/uconowner.gf?n=14769524027177477 |date=August 14, 2014 }}, Utah Department of Transportation, June 2014 * [http://showcase.gspnet.com/Showcase/Projects/Showcase-4/Bessemer-US-129-Bypass-Diverging-Diamond-Intercha Transportation engineers discuss the design of the fifth U.S. DDI in Alcoa, TN] {{Webarchive|url=https://web.archive.org/web/20110928131458/http://showcase.gspnet.com/Showcase/Projects/Showcase-4/Bessemer-US-129-Bypass-Diverging-Diamond-Intercha |date=September 28, 2011 }} * [https://www.youtube.com/watch?v=tCtAxQeR_bs Video of Paramics Traffic Simulation software modeling a Double Crossover Diamond Interchange] * [https://www.youtube.com/watch?v=HD-0QnUlLOQ Diverging Diamond Interchange Visualization], Instructional video on how to drive in a DDI, NCDOTcommunications, published on March 10, 2011 * [https://www.flickr.com/photos/26387111@N06/sets/72157621103069705 Images of Diverging Diamond Interchange in Springfield, Missouri] the first in North America. * [https://www.youtube.com/watch?v=-j3yF0G0OCQ Animation of Diverging Diamond Interchange under construction at Elmhurst Road on Interstate 90 near Elk Grove, Illinois, to be completed in 2016] * [https://www.youtube.com/watch?v=cTOiN5e8EM8 Animation of Diverging Diamond Interchange at I-590/Winton Road (Rochester, New York)]
=== Examples === * {{Coord|48.832115|N|2.152859|E|region:FR-IDF_type:landmark}}—Diverging diamond in Versailles, France * {{Coord|50.544805|N|3.055861|E|type:landmark_region:FR-59}} Diverging diamond in Seclin, France * {{Coord|37.2503|-93.3107|name=Springfield, Missouri diverging diamond interchange|display=inline|scale:3000_type:landmark_region:US-MO}}—Diverging diamond in Springfield, Missouri
{{Road junction types}}
{{DEFAULTSORT:Diverging Diamond Interchange}} Category:Road junction types