Diverging diamond interchange

Top left: Traffic enters the interchange along Missouri Route 13
Top right: Traffic crosses over to the left side of the road
Bottom left: Traffic crosses over Interstate 44
Bottom right:Traffic crosses back over to the right side of the road.

A diverging diamond interchange is a rare form of diamond interchange in which the two directions of traffic on the non-freeway road cross to the opposite side on both sides of the bridge at the freeway. It is unusual in that it requires traffic on the freeway overpass (or underpass) to briefly drive on the opposite side of the road from what they are accustomed. The diverging diamond interchange was listed by Popular Science magazine as one of the best innovations in 2009 (engineering category) in "Best of What's New 2009".^[1]

Like the continuous flow intersection, the diverging diamond interchange allows for two-phase operation at all signalized intersections within the interchange. This is a significant improvement in safety, since no left turns must clear opposing traffic and all movements are discrete, with most controlled by traffic signals.^[2] Additionally, the design can improve the efficiency of an interchange, as the lost time for various phases in the cycle can be redistributed as green time; there are only two clearance intervals (the time for traffic signals to change from green to yellow to red) instead of the six or more found in other interchange designs. Some of the intersections in the design can be unsignalized. The left turn from the freeway off-ramp, for example, can form an auxiliary lane that then becomes an exit-only lane for the entrance ramp to the freeway in the opposite direction. Omitting the traffic signals for the left turn movements off the freeway only works well with single left turns and when short queues exist within the interchange on the arterial street. A design similar to a diverging diamond interchange can also be used as a free-flowing freeway-freeway junction by replacing the traffic lights with bridges, but then it is no longer a diverging diamond, but an obsolete form of directional interchange. In the United States, such a design would violate newer federal requirements that all exit and entrance ramps be located on the right side of the freeway lanes.^{[citation needed]}

History

Another diagram illustrating traffic movements in the interchange

Prior to the last few years, the only known diverging diamond interchanges were located in France in the communities of Versailles, Le Perreux-sur-Marne, and Seclin (see External Links, below). (The ramps of the first two listed have been reconfigured to accommodate ramps of other interchanges, as seen in views on the Google Earth and Google Maps websites, but they continue to function as diverging diamond interchanges.) The interchange configuration was introduced to America in a paper submitted to the 2nd Urban Street Symposium held in Anaheim, California in 2003 by Gilbert Chlewicki, a civil engineer from Baltimore, Maryland.^[3][4] In 2009 an interchange of this type was constructed in Springfield, Missouri with additional interchanges constructed in North America in subsequent years(see below).

The interchange in Seclin (at 50°32′41″N 3°3′21″E / 50.54472°N 3.05583°E / 50.54472; 3.05583) between the A1 and Route d'Avelin appears to have been made somewhat more specialized than in the diagram at right: eastbound traffic on Route d'Avelin intending to enter the A1 northbound must keep left and cross the northernmost bridge before turning left to proceed north onto A1; eastbound traffic continuing east on Route d'Avelin must select a single center lane, merge with A1 traffic that is exiting to proceed east, and cross a center bridge. All westbound traffic that is continuing west or turning south onto A1 uses the southernmost bridge.

Additional research was conducted by a partnership of the Virginia Polytechnic Institute and State University, the Turner-Fairbank Highway Research Center and a private consultant, and the results were published by Ohio Section of the Institute of Transportation Engineers.^[5]

Advantages

• Provides for two-phase signals with short cycle lengths, significantly reducing delay.
• Reduced horizontal curvature reduces risk of off-road crashes.
• Increases the capacity of turning movements to and from the ramps.
• May potentially reduce the number of lanes on the crossroad, minimizing impacts to existing right-of-way.
• Substantially reduces the number of conflict points, thus theoretically improving safety.
• Theoretically improves pedestrian safety.
• Increases the capacity of an existing overpass or underpass, by removing the need for turn lanes.

Disadvantages

Plan of rejected diverging diamond interchange in Findlay, Ohio

• Drivers may not be familiar with configuration, particularly with regards to merging maneuvers along the left side of the roadway or the reversed flow of traffic.
• Pedestrians would be required to cross free-flowing traffic on freeway ramps. 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 at both intersections for both directions simultaneously—unless the two signalized intersections are replaced with underpass/overpass structures (an expensive proposition and usually not possible within the existing right of way of the non-freeway road).
• Exiting traffic cannot re-enter the freeway in the same direction without first leaving the interchange on the crossroad. This makes it harder to implement stops for express transit buses and means that drivers who accidentally take the wrong exit must turn around somewhere along the crossroad.
• Because of the above, emergency management can not use the exit and entrance ramps to allow freeway traffic to bypass a crash at the bridge.
• Also because of the above, an oversize load can not use the exit and entrance ramps to bypass a bridge that is too low.
• Also because of the above, a diverging diamond can not be the parent interchange for a rebound interchange without using collector-distributor roads (local-express lanes).

Further considerations

• No standards currently exist for this design and the design is extremely dependent on site-specific conditions.
• There is no crash history available in the North America region, as no DDIs existed in North America until June 21, 2009, when North America's first DDI opened to traffic in Springfield, Missouri.
• 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 45 mph (72 km/h) posted speed on the crossroad approach. However this may be mitigated by utilizing a higher design speed for the crossing movements.

Use in North America

Construction of a diverging diamond interchange in the US in Springfield, Missouri, at the intersection of I-44 and MO-13 (at 37°15′01″N 93°18′39″W / 37.2503°N 93.3107°W / 37.2503; -93.3107 (Springfield, Missouri diverging diamond interchange)) began the week of January 12, 2009, and the interchange opened on Sunday, June 21, 2009, making it the first of its kind to be opened in the United States.^[6][7] This interchange was a conversion of an existing standard diamond interchange. MoDOT completed a second diverging diamond interchange in Springfield at U.S. 60 and National Avenue in July 2010.^[8] There are also plans to reconfigure the intersection of U.S. 65 and Chestnut Expressway (Business Route 65) into a diverging diamond configuration.^[9]

The Utah Department of Transportation completed its first diverging diamond interchange in August 2010 at Main Street in American Fork.^[10] UDOT has two more open (see below), and is currently constructing one more diverging diamond, at American Fork 500 East, as part of the reconstruction of I-15.^[11].

The Missouri Department of Transportation has completed the new diverging diamond interchange at I-270 and Dorsett Road in St. Louis County in late 2010. http://www.270dorsettpage.com/

The Tennessee Department of Transportation designed a diverging diamond as part of the US 129 Bypass / Bessemer St / Middlesettlements Rd Interchange in Alcoa. The interchange opened on December 12, 2010, becoming the 5th operational diverging diamond in the country.^[12]

In Lexington, Kentucky, North America's sixth diverging diamond interchange opened on August 14, 2011, at the intersection of Harrodsburg Road and New Circle Road. ^[13]

In Lehi, Utah, North America's seventh diverging diamond interchange opened on August 15, 2011, at the intersection of the Timpagonos Highway (Utah 92) and Interstate 15. While still under construction, it began operating as a diverging diamond on this date. UDOT was the first to reconfigure an interchange to a diverging diamond using existing infrastructure at this location.^[14]

In Salt Lake County, just outside Salt Lake, Utah, North America's eighth diverging diamond interchange opened on October 23, 2011, at the intersection of Utah 201 and the Bangarter Highway (Utah 154).

The Idaho Transportation Department has proposed a diverging diamond interchange to replace the existing Chubbuck interchange on Interstate 86. Construction is slated to begin in 2013 and finish in 2015.^[15]

A diverging-diamond interchange is nearing completion for the future interchange at US Hwy 52 and Olmsted County Rd. 12 in Pine Island, Minnesota, just a few miles north of the city of Rochester.^[16] It will be the first diverging-diamond in Minnesota. Two other projects are being studied, one in Sartell, near St. Cloud, and the other near Elko.

Possible future use in North America

Southern approach to the I-44/Route 13 interchange in Springfield.

The Missouri Department of Transportation has plans to build additional diverging diamond interchanges across the state: In Kansas City at the intersection of I-70 and Woods Chapel Road, at the intersection of I-435 and Front Street, and at the intersection of Botts Road and M-150; and one in St. Louis County at the intersection of I-270 and Dorsett Road.^[17] The I-270 and Dorsett intersection opened for the first time on October 2010 becoming the 4th Diverging Diamond in the country.^[18] The city of Branson, Missouri has decided to use the interchange at the intersection of MO 248 and US 65.^[19] Others are planned in Kansas City (I-29 & Tiffany Springs Parkway), Harrisonville (US 71 & Route 291), Grain Valley (I-70 & Route AA), Ozark, O'Fallon, Farmington, and St Peters.

The Virginia Department of Transportation has proposed to reconstruct the 0.49 mile stretch of US-15 where it meets I-64 at Zion Crossroads as a diverging diamond interchange. VDOT anticipates construction to begin in 2012. ^[20] VDOT also proposes constructing a diverging diamond interchange at the intersection of U.S. 460 and Southgate Drive in Blacksburg, replacing the only remaining at-grade intersection on the freeway-standard bypass of Blacksburg and Christiansburg.^[21]

This type of interchange was studied and rejected for use in Maryland along the Baltimore-Washington Parkway in Anne Arundel County, near the Baltimore-Washington International Thurgood Marshall Airport.^[22]

The Ontario Ministry of Transportation is studying a diverging diamond as part of interchange upgrades at Highway 427 and Rathburn Road in Toronto.^[23]

In February 2007, the Oregon Department of Transportation accepted the DDI as the preferred alternative at Exit 24 (Fern Valley Road) along I-5 in Phoenix, in the southern area of Oregon. It will begin construction in 2012.^[24][25] A second diverging diamond interchange is being studied for Ashland.

In 2009, the Indiana Department of Transportation announced plans to build a diverging diamond interchange near Watson, Indiana in Clark county, as part of the Ohio River Bridges Project. It will replace the current interchange at Indiana 265 and Indiana 62. The engineering for this project is almost completed. Another diverging diamond is being studied north of Fort Wayne, Indiana.

In 2008, New York State Department of Transportation (NYSDOT) announced that they were studying this alternative as a possibility for the I-590 / Winton Rd. interchange in Rochester.^[26] On February 19, 2010, NYSDOT officially announced plans to build the diverging diamond interchange, to be completed in Summer of 2012.^[27]

The Ohio Department of Transportation (ODOT) has considered employing the interchange. ODOT planned to reconstruct the I-75/US-224/SR-15 interchange in Findlay to this configuration, but reconsidered.^[28] The agency is currently considering the configuration for the I-480/Tiedeman Road interchange in Brooklyn.^[29][30]

Five diverging diamonds are proposed in Georgia at the Ashford-Dunwoody Road interchange and bridge over I-285 in Atlanta, the SR 120/Duluth Highway bridge and interchange over SR 316 in Lawrenceville, the SR 317/Lawrenceville-Suwanee Road interchange and bridge over I-85 in Suwanee and for the Jimmy Carter Boulevard and Pleasant Hill Road interchanges and bridges over I-85 Interstate 85 in Gwinnett County, to the northeast of Atlanta.^[31]

On April 6, 2010, the Charlotte suburb of Cornelius approved plans by the North Carolina Department of Transportation to convert the existing diamond interchange into a diverging diamond at the West Catawba/Catawba Exit (#28). This will be the first one in the state of North Carolina. Work is expected to finish by 2012.^[32] North Carolina has also designed three other diverging diamonds in the Charlotte area, two on I-85 and one on I-485, and is studying diverging diamonds at Asheville, Kernersville, Lumberton, and Leland, for a total of eight projects in North Carolina.

Pennsylvania has two projects under study, Us 222 and Broadcasting Road at Reading, and US 222 and US 322 near Ephrata. Idaho has one near Pocatello, where US 91 meets I-86.

There is a sort of half-diverging-diamond interchange between Interstate 95 and Thurbers Ave. in Providence, Rhode Island (at 41°48′02″N 71°24′10″W / 41.800523°N 71.402823°W / 41.800523; -71.402823 (half-diverging-diamond interchange)). The extension of Thurbers Ave. to US Route 1 being a one-way prevents it from being a full diverging diamond, but the interchange directly with Route 1 keeps almost full functionality, lacking only an easy-access interchange from US 1 to I-95 South.

A diverging diamond has been proposed in Illinois at the interchange of IL-59 and I-88 in Naperville.^[33]

Florida is studying two locations near Sarasota, and a third farther south on I-75.

The Kansas Department of Transportation is currently working with Burns & McDonnell Engineering Company to design a Diverging Diamond Interchange for a new interchange on I-35 at Homestead Lane in Johnson County Kansas (http://i35swjohnsoncointerchange.ksdot.org/DDI.aspx)

The town of Colchester, Vermont is considering a double-crossover diamond interchange as a replacement for the current intersection of exit 16 of Interstate 89.^[34][35]

See also

• Continuous-flow intersection
• Jughandle
• Hook turn
• Michigan left
• Superstreet

References

1. ^ http://www.popsci.com/node/42027
2. ^ "OHM – Diverging Diamond Interchange". http://www.ohm-advisors.com/ddi/index.cfm. 
3. ^ Chlewicki, Gilbert (2003). "New Interchange and Intersection Designs: The Synchronized Split-Phasing Intersection and the Diverging Diamond Interchange" (PDF). http://www.urbanstreet.info/2nd_sym_proceedings/Volume%202/Chlewicki.pdf. Retrieved 2009-10-20. 
4. ^ http://www.divergingdiamond.com/about.html
5. ^ Diverging Diamond Interchange and Double Crossover Intersection – Vehicle and Pedestrian Performance by Praveen K. Edara, Joe G. Bared, and Ramanujan Jagannathan. Undated.
6. ^ "I-44/Route 13 Interchange Reconstruction: Diverging Diamond Design". MoDOT. 2009-04. http://www.modot.org/springfield/major_projects/Greene/I-44andRoute13.html. Retrieved 2009-05-19. 
7. ^ "Public Meeting Tuesday, June 24, On I-44/Route 13 Reconstruction To Reduce Congestion, Improve Safety" (Press release). MoDOT. 2008-06-19. http://www.modot.org/springfield/news_and_information/District8News.shtml?action=displaySSI&newsId=19484. Retrieved 2008-06-19. 
8. ^ http://www.douglascountyherald.com/?p=3928
9. ^ "U.S. 65/Chestnut Exp. (Bus. 65) Interchange Reconstruction". MoDOT. 2008-09. http://www.modot.mo.gov/springfield/major_projects/Greene/ChestnutExp65.html. Retrieved 2009-05-19. 
10. ^ http://www.udot.utah.gov/access/
11. ^ http://i15core.utah.gov/InteractiveMap/
12. ^ http://www.wbir.com/news/article/147189/2/TDOT-to-open-Diverging-Diamond-on-Saturday-?odyssey=tab%7Ctopnews%7Ctexth%7CFRONTPAGE%7Cdefault%7Cp
13. ^ url=http://www.kentucky.com/2011/08/15/1846182/motorists-navigate-new-harrodsburg.html
14. ^ http://www.udot.utah.gov/sr92/
15. ^ url=http://apps.itd.idaho.gov/Apps/MediaManagerViewer/NewsRelease/NewsRelease.aspx?Id=3252
16. ^ http://www.dot.state.mn.us/elkrun/index.html
17. ^ "I-270 and Dorsett Road Interchange Project". http://www.modot.org/stlouis/major_projects/I-270andDorsettInterchangeProject.htm. Retrieved 2008-04-08. 
18. ^ "New Dorsett Road diverging diamond open to traffic". http://www.ksdk.com/news/local/story.aspx?storyid=222255&catid=3. Retrieved 2010-10-18. 
19. ^ http://www.viewbranson.com/?q=content/action-taken-branson-board-aldermen-january-26-2010-meeting
20. ^ "Proposed: I-64 Interchange at Route 15, Zion Crossroads". virginiadot.org: Projects & Studies. http://www.virginiadot.org/projects/culpeper/i-64_zion_crossroads_interchange.asp. Retrieved 11 June 2011. 
21. ^ "Final Southgate Interchange Study". 2 June 2011. http://www.montva.com/filestorage/1146/98/157/658/Southgate_Report_Final_06_02_2011.pdf. Retrieved 16 October 2011. 
22. ^ "Project Planning Study". Maryland State Highway Administration. 2009-05-12. http://www.sha.state.md.us/WebProjectLifeCycle/ProjectInformation.asp?projectno=AA372112. Retrieved 2009-05-19. ^{[dead link]}
23. ^ McGran, Kevin (2006-05-25). "Radical fix posed for region's roads; Ministry weighs driving on the left". Toronto Star. http://pqasb.pqarchiver.com/thestar/access/1041799251.html?FMT=ABS. Retrieved 2008-07-21. 
24. ^ Mail Tribune - At last, a solution - February 9, 2007
25. ^ Southwestern Oregon Fern Valley Interchange
26. ^ Unique Intersection Discussed in Brighton - 13WHAM.com
27. ^ NYSDOT - I590 Winton Road Interchange
28. ^ "Wrong Way? Not in Kansas City", Land Line Magazine, March 31, 2006.
29. ^ Noga, Joe (2008-04-10). "Traffic support: Kucinich lobbies for Tiedeman solution". Brooklyn Sun Journal. http://www.cleveland.com/brooklynsunjournal/news/index.ssf?/base/news-0/120776695687570.xml&coll=4. Retrieved 2008-07-21. 
30. ^ Farkas, Karen (2008-11-07). "Could this diamond ease rough traffic?". The Plain Dealer. http://infoweb.newsbank.com/iw-search/we/InfoWeb?p_action=doc&p_topdoc=1&p_docnum=1&p_sort=YMD_date:D&p_product=NewsBank&p_text_direct-0=document_id=(%20124554E274C69308%20)&p_docid=124554E274C69308&p_theme=aggregated5&p_queryname=124554E274C69308&f_openurl=yes&p_nbid=S62X61XVMTIyNjUzMzQ4NS44NDk3Nzg6MToxMjoxOTguMzAuMjI4LjA&&p_multi=CPDB. Retrieved 2008-11-12. 
31. ^ Fox, Patrick (February 14, 2010). "New design could ease Gwinnett bottlenecks". Atlanta Journal-Constitution. http://www.ajc.com/news/gwinnett/new-design-could-ease-304470.html. Retrieved 15 February 2010. 
32. ^ "Cornelius getting N.C.'s first 'Diverging Diamond' interchange". Charlotte Observer. Marusak. http://www.charlotteobserver.com/2010/04/06/1360024/cornelius-getting-unique-i-77.html. Retrieved 6 April 2010. ^{[dead link]}
33. ^ Wronski, Richard (July 25, 2010). "'Diverging diamond' could cut congestion at Illinois 59 and I-88". Chicago Tribune. http://www.chicagotribune.com/classified/automotive/ct-met-naperville-interchange-0726-20100725,0,126148,full.story. Retrieved 25 July 2010. 
34. ^ "Interstate 89 Exit 16 Scoping Study". Chittenden County Metropolitan Planning Organization. http://www.ccmpo.org/I89/Exit16/. 
35. ^ Davenport, Melinda. "Busy I-89 exit could get a makeover". WCAX News. http://www.wcax.com/story/14708658/busy-i-89-exit-could-get-a-makeover. Retrieved May 24, 2011. 

http://www.270dorsettpage.com/

Further reading

• "Drivers' Evaluation of the Diverging Diamond Interchange" (publication number FHWA-HRT-07-048). Turner-Fairbank Highway Research Center, Federal Highway Administration
• "Diamond interchange planned for So. Indiana project", courier-journal.com, January 19, 2010
• "Missouri's Experience with a Diverging Diamond Interchange: Lessons Learned, MoDOT Innovations Library, May 2010

External links

• Utah Department of Transportation Timpanogos Highway Diverging Diamond Interchange animation video
• Transportation engineers discuss the design of the fifth U.S. DDI in Alcoa, TN
• Video of Double Crossover Diamond Interchange (new name for DDI) currently under construction in Lexington, Kentucky.
• Video of Paramics Traffic Simualtion software modeling a Double Crossover Diamond Interchange
• Images of Diverging Diamond Interchange in Springfield, Missouri the first in North America.
• Animation of diverging diamond interchange at Dorsett and Interstate 270 in St. Louis.
• Web page for Springfield Missouri Diverging Diamond Interchange
• Web page for Missouri DDI at I-435 and Front st.
• 48°49′56″N 2°09′10″E / 48.832115°N 2.152859°E / 48.832115; 2.152859 Map of a diverging diamond interchange in Versailles, France
• 48°49′49.1″N 2°29′35.3″E / 48.830306°N 2.493139°E / 48.830306; 2.493139 Map of a diverging diamond interchange in Le Perreux-sur-Marne, France
• 50°32′41.2″N 3°3′20.9″E / 50.544778°N 3.055806°E / 50.544778; 3.055806 Map of a diverging diamond interchange in Seclin, France