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Diamond interchange

April 25, 2023

A diamond interchange is a common type of road junction, used where a controlled-access highway crosses a minor road.

Visual showing how diamond interchanges are used, with an expressway running across and a local road running in the center. Left image is for left-side traffic (UK), right image is for right-side traffic (US). Large arrows show where turns are made; smaller arrows show traffic flow.

Design

 
A typical diamond interchange

The freeway itself is grade-separated from the minor road, one crossing the other over a bridge. Approaching the interchange from either direction, an off-ramp diverges only slightly from the freeway and runs directly across the minor road, becoming an on-ramp that returns to the freeway in similar fashion.

 
Illinois Route 68 approaching a diamond interchange with U.S. Route 14 in Barrington, Illinois

The two places where the ramps meet the road are treated as conventional intersections. In the United States, where this form of interchange is very common, particularly in rural areas, traffic on the off-ramp typically faces a stop sign at the minor road, while traffic turning onto the freeway is unrestricted.

The diamond interchange uses less space than most types of freeway interchange, and avoids the interweaving traffic flows that occur in interchanges such as the cloverleaf. Thus, diamond interchanges are most effective in areas where traffic is light and a more expensive interchange type is not needed. But where traffic volumes are higher, the two intersections within the interchange often feature additional traffic control measures such as traffic lights and extra lanes dedicated to turning traffic.

The at-grade variant of the diamond interchange is the split intersection.

Variations

Dumbbell

For the at-grade intersection design analogous to dumbbell and dogbone interchanges, see Bowtie (road).
 
A dumbbell interchange along Ontario Highway 401 in Clarington
43°53′3″N 78°43′20″W / 43.88417°N 78.72222°W / 43.88417; -78.72222

The ramp intersections may also be configured as a pair of roundabouts[1] to create a type of diamond interchange often called a dumbbell interchange[2][unreliable source?] (due to its aerial resemblance to a dumbbell), and sometimes called a double roundabout interchange.[3][1] Because roundabouts can generally handle traffic with fewer approach lanes than other intersection types, interchange construction costs can be reduced by eliminating the need for a wider bridge. This configuration allows other roads to form approach legs to the roundabouts and also allows easy U-turns.[4]

This type of interchange is common in the United Kingdom and Ireland, and is becoming increasingly common in the United States. Examples of dumbbell interchanges in the United States are located on Interstate 35 in Medford, Minnesota, on Interstate 87 in Malta, New York, on Interstate 17 at Happy Valley Road north of Phoenix, Arizona, and on Interstate 80 at California State Route 89 (exit 185) in Truckee, California. An example in Canada is found on the Pat Bay Highway in North Saanich, British Columbia, near Victoria International Airport.

One or both roundabouts in the dumbbell interchange may also contain side lanes to increase the capacity. A good example of such a "turbo" dumbbell interchange, which was formerly a half cloverleaf, can be seen in Jülich, Germany at 50°54′51″N 6°19′24″E / 50.914055°N 6.323368°E / 50.914055; 6.323368.

There are interchanges similar to dumbbells in which the ramps do not meet the roundabouts at intersections; these more closely resemble bowtie intersections. One such interchange exists at the junction between the Ruta Interbalnearia and Route 35 North near La Floresta, Uruguay (34°44′58″S 55°40′39″W / 34.7495°S 55.6775°W / -34.7495; -55.6775).

Dogbone

A variation of the dumbbell interchange, often called a dogbone interchange (due to its aerial resemblance to a real or toy dog bone), and sometimes also called a double roundabout interchange,[1] occurs when the roundabouts do not form a complete circle but instead have a "raindrop" or "teardrop" shape. These two raindrop roundabouts are fused together, forming a single "squashed" roundabout.

This configuration reduces conflicts between vehicles entering the raindrop roundabouts from the ramps, reducing queueing and delays, compared with the dumbbell interchange. Direct U-turns are not possible, although the movement can be made by circulating around both raindrop roundabouts.[4] An example of a dogbone interchange in the United States is located on Interstate 70 in Avon, Colorado, United States;[5] more compact examples, which show less of the characteristic "dog bone" shape, are located along Keystone Parkway in Carmel, Indiana, United States. Several interchanges similar to those along Keystone Parkway are being built along the new US 31 freeway under construction in northern Indiana.[6]

There are some hybrid interchanges of dumbbell and dogbone having one raindrop and one full roundabout. This is made when the roundabout intersects more roads than the cross street and ramps. Some examples are at exit 38 of the N7 road in Groningen, Netherlands (at 53°12′53″N 6°36′09″E / 53.21462°N 6.602509°E / 53.21462; 6.602509); and Ennis Avenue (National Route 1) at Safety Bay Road (State Route 18 / Tourist Drive 202) on the border of the suburbs of Waikiki and Warnbro in the City of Rockingham, Western Australia (at 32°19′29″S 115°46′01″E / 32.32486°S 115.76704°E / -32.32486; 115.76704).

A tennis ball interchange resembles a dogbone interchange, with the difference being that right turning movements (in a country where traffic drives on the left) cut through the roundabouts like a regular diamond interchange instead of going around the roundabout. Such a design is found in Perth, Western Australia, between Roe Highway (State Route 3) and Berkshire Road (at 31°58′10″S 116°00′04″E / 31.96945°S 116.00107°E / -31.96945; 116.00107).[7]

Tight diamond

 
A tight urban diamond interchange (TUDI)

A tight diamond interchange (TDI), also known as a compressed diamond interchange or a tight urban diamond interchange (TUDI), is sometimes used in areas where there is insufficient right-of-way for a standard diamond interchange. The pair of intersections where the ramps meet the minor road are closely spaced.[1][8] This spacing forces the turn lanes for each direction to run beside each other, causing the minor road to be wider than it would be if it were a standard diamond.[citation needed] Caltrans classifies this type as Type L-1.[9]

Single-point urban

 
Single-point urban interchange near Orlando, Florida, dismantled in the early 2010s
28°33′13.7″N 81°16′11.6″W / 28.553806°N 81.269889°W / 28.553806; -81.269889

A single-point urban interchange (SPUI) is built with a large over- or clear underpass providing space for a single traffic signal controlled intersection with the ramps and the cross street. Caltrans classifies this type as Type L-13.[9]

Contraflow left

 
A contraflow left turn interchange

A contraflow left interchange (CFL) is a modified TUDI, once installed at Lyons Road underneath Florida State Road 869, switching the left turn lanes on the cross street each other and bringing the long left turn phases from the single-point urban interchange to the tight urban diamond interchange at 26°18′04″N 80°11′11″W / 26.301177°N 80.186479°W / 26.301177; -80.186479.[10][11]

Diverging diamond

In a diverging diamond interchange (DDI) or (DCD), the two directions of traffic on the non-freeway road cross to the opposite side on both sides of the bridge at the freeway to save the third traffic signal phase.

Three-level diamond

In a three-level diamond interchange, the cross street is built in a third level with free flowing traffic as a second arterial road. The intersection is split up into four intersections, handling just two conflicting directions each.

Its two-level variant is the split diamond interchange.

Its at-grade variant is the town center intersection (TCI).

Continuous-flow diamond

 
Continuous-flow diamond

A single-leg continuous-flow intersection (CFI) was built in 2014 in San Marcos, Texas, at the intersection of Aquarena Springs Drive (Loop 82), Interstate 35's southbound frontage road and I-35's southbound-to-northbound Texas U-turn.[12][13] A two-leg CFI, also in San Marcos, was built in 2015 at the intersection of Hopkins Street (State Highway 80), I-35's frontage roads and I-35's Texas U-turns.[14] In both intersections, the displaced left turn lanes merge with the Texas U-turn lanes.

Split diamond

 
Split diamond interchange

A split diamond interchange has its ramps "split" between two crossroads, typically with an exit ramp/entrance ramp pair serving each of the crossroads. The crossroads themselves may be one-way or two-way, and are most often connected by frontage roads, usually one-way.[15][16]

Other

Where HOV lanes are present for carpooling, the ramps of a diamond interchange may be folded to the inside lanes instead of the outside. In urban areas this saves some space as well as requiring only one intersection instead of the two one-way intersections, which in rural or suburban areas can be turned into a single-point urban interchange. This in turn reduces waiting time for motorists at traffic lights on the smaller road, which may be a large local thoroughfare with heavy traffic.

See also

References

  1. ^ a b c d Staff (April 2010). "Chapter 9: Other Interchange Configurations". Alternative Intersections/Interchanges: Informational Report (AIIR). Federal Highway Administration. FHWA-HRT-09-060. Retrieved October 8, 2012.
  2. ^ Marshall, Chris (2012). . Chris's British Road Directory. Self-published. Archived from the original on January 18, 2013. Retrieved February 25, 2013.
  3. ^ Federal Highway Administration (FHWA): Manual on Uniform Traffic Control Devices (MUTCD), Edition 2009, Revision 2, May 2012], Figure 3C-14. Example of Markings for a Diamond Interchange with Two Circular-Shaped, Roundabout Ramp Terminals, p.412 (PDF p.452)
  4. ^ a b . An Applied Technology and Traffic Analysis Program: Unconventional Arterial Intersection Design. University of Maryland, College Park / Maryland State Highway Administration. 2011. Archived from the original on December 24, 2013. Retrieved February 25, 2013.
  5. ^ Google. "Teardrop roundabout in Avon, CO" (Map). Google Maps. Google.
  6. ^ "The New US 31 Hamilton County: Frequently Asked Questions". Hamilton County, Indiana. March 2015. Retrieved December 3, 2015.
  7. ^ "Roe Highway / Berkshire Road Interchange" (PDF). Gateway WA. Gateway WA. April 2015. (PDF) from the original on September 26, 2015. Retrieved September 26, 2015.
  8. ^ Staff (August 2004). "Chapter 10: Alternative Intersection Treatments". Signalized Intersections: Informational Guide. Federal Highway Administration. FHWA-HRT-04-091. Retrieved October 8, 2012.
  9. ^ a b https://dot.ca.gov/-/media/dot-media/programs/design/documents/chp0500-032020.pdf[bare URL PDF]
  10. ^ Chatterjee, Indrajit & Sharma, Siddharth (2007). Comparative Analysis of Conventional Diamond Interchange and Contra Flow Left Turn (CFL) Interchange (Report). Center for Transportation Research and Education at Iowa State University. S2CID 108139034.
  11. ^ ATTAP (March 9, 2017). "Unconventional Intersection/Interchange Designs & Strategies". Contraflow Left Interchange. University of Maryland. Retrieved July 15, 2017.
  12. ^ Amada Dugan: San Marcos opens up region’s first continuous flow intersection KXAN News, 30 April 2014.
  13. ^ Intersection Improvements to SH 80 and Loop 82 at I-35 777 E Hopkins St, Texas State University, retrieved 30 December 2014.
  14. ^ TxDOT to modify recently completed I-35, Hopkins Street interchange, San Marcos Mercury, 18 May 2015.
  15. ^ Staff (April 24, 2012). "Interchange Design Promptlist". Federal Highway Administration, Missouri Division. Retrieved November 27, 2017.
  16. ^ Garcia, Rene, P.E. (October 1, 2014). "Freeways". Roadway Design Manual. Texas Department of Transportation. Chapter 3: New Location and Reconstruction (4R) Design Criteria, Section 6. Retrieved November 27, 2017.

External links

  • City of Carmel, Indiana, USA, Roundabouts (or dogbone interchanges) page
  • Diverging Diamond Interchange Informational Guide Federal Highway Administration

April 25, 2023
diamond, interchange, diamond, interchange, common, type, road, junction, used, where, controlled, access, highway, crosses, minor, road, visual, showing, diamond, interchanges, used, with, expressway, running, across, local, road, running, center, left, image. A diamond interchange is a common type of road junction used where a controlled access highway crosses a minor road Visual showing how diamond interchanges are used with an expressway running across and a local road running in the center Left image is for left side traffic UK right image is for right side traffic US Large arrows show where turns are made smaller arrows show traffic flow Contents 1 Design 2 Variations 2 1 Dumbbell 2 2 Dogbone 2 3 Tight diamond 2 4 Single point urban 2 5 Contraflow left 2 6 Diverging diamond 2 7 Three level diamond 2 8 Continuous flow diamond 2 9 Split diamond 2 10 Other 3 See also 4 References 5 External linksDesign Edit A typical diamond interchange The freeway itself is grade separated from the minor road one crossing the other over a bridge Approaching the interchange from either direction an off ramp diverges only slightly from the freeway and runs directly across the minor road becoming an on ramp that returns to the freeway in similar fashion Illinois Route 68 approaching a diamond interchange with U S Route 14 in Barrington Illinois The two places where the ramps meet the road are treated as conventional intersections In the United States where this form of interchange is very common particularly in rural areas traffic on the off ramp typically faces a stop sign at the minor road while traffic turning onto the freeway is unrestricted The diamond interchange uses less space than most types of freeway interchange and avoids the interweaving traffic flows that occur in interchanges such as the cloverleaf Thus diamond interchanges are most effective in areas where traffic is light and a more expensive interchange type is not needed But where traffic volumes are higher the two intersections within the interchange often feature additional traffic control measures such as traffic lights and extra lanes dedicated to turning traffic The at grade variant of the diamond interchange is the split intersection Variations EditDumbbell Edit For the at grade intersection design analogous to dumbbell and dogbone interchanges see Bowtie road A dumbbell interchange along Ontario Highway 401 in Clarington43 53 3 N 78 43 20 W 43 88417 N 78 72222 W 43 88417 78 72222 The ramp intersections may also be configured as a pair of roundabouts 1 to create a type of diamond interchange often called a dumbbell interchange 2 unreliable source due to its aerial resemblance to a dumbbell and sometimes called a double roundabout interchange 3 1 Because roundabouts can generally handle traffic with fewer approach lanes than other intersection types interchange construction costs can be reduced by eliminating the need for a wider bridge This configuration allows other roads to form approach legs to the roundabouts and also allows easy U turns 4 This type of interchange is common in the United Kingdom and Ireland and is becoming increasingly common in the United States Examples of dumbbell interchanges in the United States are located on Interstate 35 in Medford Minnesota on Interstate 87 in Malta New York on Interstate 17 at Happy Valley Road north of Phoenix Arizona and on Interstate 80 at California State Route 89 exit 185 in Truckee California An example in Canada is found on the Pat Bay Highway in North Saanich British Columbia near Victoria International Airport One or both roundabouts in the dumbbell interchange may also contain side lanes to increase the capacity A good example of such a turbo dumbbell interchange which was formerly a half cloverleaf can be seen in Julich Germany at 50 54 51 N 6 19 24 E 50 914055 N 6 323368 E 50 914055 6 323368 There are interchanges similar to dumbbells in which the ramps do not meet the roundabouts at intersections these more closely resemble bowtie intersections One such interchange exists at the junction between the Ruta Interbalnearia and Route 35 North near La Floresta Uruguay 34 44 58 S 55 40 39 W 34 7495 S 55 6775 W 34 7495 55 6775 Dogbone Edit A dogbone interchange along Interstate 26 in Columbus North Carolina United States35 14 43 7 N 82 12 20 2 W 35 245472 N 82 205611 W 35 245472 82 205611 A variation of the dumbbell interchange often called a dogbone interchange due to its aerial resemblance to a real or toy dog bone and sometimes also called a double roundabout interchange 1 occurs when the roundabouts do not form a complete circle but instead have a raindrop or teardrop shape These two raindrop roundabouts are fused together forming a single squashed roundabout This configuration reduces conflicts between vehicles entering the raindrop roundabouts from the ramps reducing queueing and delays compared with the dumbbell interchange Direct U turns are not possible although the movement can be made by circulating around both raindrop roundabouts 4 An example of a dogbone interchange in the United States is located on Interstate 70 in Avon Colorado United States 5 more compact examples which show less of the characteristic dog bone shape are located along Keystone Parkway in Carmel Indiana United States Several interchanges similar to those along Keystone Parkway are being built along the new US 31 freeway under construction in northern Indiana 6 There are some hybrid interchanges of dumbbell and dogbone having one raindrop and one full roundabout This is made when the roundabout intersects more roads than the cross street and ramps Some examples are at exit 38 of the N7 road in Groningen Netherlands at 53 12 53 N 6 36 09 E 53 21462 N 6 602509 E 53 21462 6 602509 and Ennis Avenue National Route 1 at Safety Bay Road State Route 18 Tourist Drive 202 on the border of the suburbs of Waikiki and Warnbro in the City of Rockingham Western Australia at 32 19 29 S 115 46 01 E 32 32486 S 115 76704 E 32 32486 115 76704 A tennis ball interchange resembles a dogbone interchange with the difference being that right turning movements in a country where traffic drives on the left cut through the roundabouts like a regular diamond interchange instead of going around the roundabout Such a design is found in Perth Western Australia between Roe Highway State Route 3 and Berkshire Road at 31 58 10 S 116 00 04 E 31 96945 S 116 00107 E 31 96945 116 00107 7 Tight diamond Edit A tight urban diamond interchange TUDI A tight diamond interchange TDI also known as a compressed diamond interchange or a tight urban diamond interchange TUDI is sometimes used in areas where there is insufficient right of way for a standard diamond interchange The pair of intersections where the ramps meet the minor road are closely spaced 1 8 This spacing forces the turn lanes for each direction to run beside each other causing the minor road to be wider than it would be if it were a standard diamond citation needed Caltrans classifies this type as Type L 1 9 Single point urban Edit Single point urban interchange near Orlando Florida dismantled in the early 2010s28 33 13 7 N 81 16 11 6 W 28 553806 N 81 269889 W 28 553806 81 269889 A single point urban interchange SPUI is built with a large over or clear underpass providing space for a single traffic signal controlled intersection with the ramps and the cross street Caltrans classifies this type as Type L 13 9 Contraflow left Edit A contraflow left turn interchange A contraflow left interchange CFL is a modified TUDI once installed at Lyons Road underneath Florida State Road 869 switching the left turn lanes on the cross street each other and bringing the long left turn phases from the single point urban interchange to the tight urban diamond interchange at 26 18 04 N 80 11 11 W 26 301177 N 80 186479 W 26 301177 80 186479 10 11 Diverging diamond Edit In a diverging diamond interchange DDI or DCD the two directions of traffic on the non freeway road cross to the opposite side on both sides of the bridge at the freeway to save the third traffic signal phase Three level diamond Edit In a three level diamond interchange the cross street is built in a third level with free flowing traffic as a second arterial road The intersection is split up into four intersections handling just two conflicting directions each Its two level variant is the split diamond interchange Its at grade variant is the town center intersection TCI Continuous flow diamond Edit Continuous flow diamond A single leg continuous flow intersection CFI was built in 2014 in San Marcos Texas at the intersection of Aquarena Springs Drive Loop 82 Interstate 35 s southbound frontage road and I 35 s southbound to northbound Texas U turn 12 13 A two leg CFI also in San Marcos was built in 2015 at the intersection of Hopkins Street State Highway 80 I 35 s frontage roads and I 35 s Texas U turns 14 In both intersections the displaced left turn lanes merge with the Texas U turn lanes Split diamond Edit Split diamond interchange A split diamond interchange has its ramps split between two crossroads typically with an exit ramp entrance ramp pair serving each of the crossroads The crossroads themselves may be one way or two way and are most often connected by frontage roads usually one way 15 16 Other Edit Where HOV lanes are present for carpooling the ramps of a diamond interchange may be folded to the inside lanes instead of the outside In urban areas this saves some space as well as requiring only one intersection instead of the two one way intersections which in rural or suburban areas can be turned into a single point urban interchange This in turn reduces waiting time for motorists at traffic lights on the smaller road which may be a large local thoroughfare with heavy traffic See also Edit Roads portalReferences Edit Diamond interchange on US 35 to I 71 in Jeffersonville Ohio at 39 37 10 N 83 36 28 W 39 61945 N 83 607858 W 39 61945 83 607858 a b c d Staff April 2010 Chapter 9 Other Interchange Configurations Alternative Intersections Interchanges Informational Report AIIR Federal Highway Administration FHWA HRT 09 060 Retrieved October 8 2012 Marshall Chris 2012 Interchanges Dumbbell Interchange Chris s British Road Directory Self published Archived from the original on January 18 2013 Retrieved February 25 2013 Federal Highway Administration FHWA Manual on Uniform Traffic Control Devices MUTCD Edition 2009 Revision 2 May 2012 Figure 3C 14 Example of Markings for a Diamond Interchange with Two Circular Shaped Roundabout Ramp Terminals p 412 PDF p 452 a b Double Roundabout Interchange Design and Operations An Applied Technology and Traffic Analysis Program Unconventional Arterial Intersection Design University of Maryland College Park Maryland State Highway Administration 2011 Archived from the original on December 24 2013 Retrieved February 25 2013 Google Teardrop roundabout in Avon CO Map Google Maps Google The New US 31 Hamilton County Frequently Asked Questions Hamilton County Indiana March 2015 Retrieved December 3 2015 Roe Highway Berkshire Road Interchange PDF Gateway WA Gateway WA April 2015 Archived PDF from the original on September 26 2015 Retrieved September 26 2015 Staff August 2004 Chapter 10 Alternative Intersection Treatments Signalized Intersections Informational Guide Federal Highway Administration FHWA HRT 04 091 Retrieved October 8 2012 a b https dot ca gov media dot media programs design documents chp0500 032020 pdf bare URL PDF Chatterjee Indrajit amp Sharma Siddharth 2007 Comparative Analysis of Conventional Diamond Interchange and Contra Flow Left Turn CFL Interchange Report Center for Transportation Research and Education at Iowa State University S2CID 108139034 ATTAP March 9 2017 Unconventional Intersection Interchange Designs amp Strategies Contraflow Left Interchange University of Maryland Retrieved July 15 2017 Amada Dugan San Marcos opens up region s first continuous flow intersection KXAN News 30 April 2014 Intersection Improvements to SH 80 and Loop 82 at I 35 777 E Hopkins St Texas State University retrieved 30 December 2014 TxDOT to modify recently completed I 35 Hopkins Street interchange San Marcos Mercury 18 May 2015 Staff April 24 2012 Interchange Design Promptlist Federal Highway Administration Missouri Division Retrieved November 27 2017 Garcia Rene P E October 1 2014 Freeways Roadway Design Manual Texas Department of Transportation Chapter 3 New Location and Reconstruction 4R Design Criteria Section 6 Retrieved November 27 2017 External links EditCity of Carmel Indiana USA Roundabouts or dogbone interchanges page Diverging Diamond Interchange Informational Guide Federal Highway Administration Retrieved from https en wikipedia org w index php title Diamond interchange amp oldid 1135105510, wikipedia, wiki, book, books, library,

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