![I-75 US 224 interchange](https://upload.wikimedia.org/wikipedia/commons/2/2c/I-75_US_224_interchange.png)
A diverging diamond interchange (DDI), also called a double crossover diamond interchange (DCD),
is a subset of
diamond interchange
A diamond interchange is a common type of road junction, used where a controlled-access highway crosses a minor road.
Design
The freeway itself is grade-separated from the minor road, one crossing the other over a bridge. Approaching the ...
in which the opposing directions of travel on the non-
freeway
A controlled-access highway is a type of highway that has been designed for high-speed vehicular traffic, with all traffic flow—ingress and egress—regulated. Common English terms are freeway, motorway and expressway. Other similar terms ...
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
Left-hand traffic (LHT) and right-hand traffic (RHT) are the practices, in bidirectional traffic, of keeping to the left side or to the right side of the road, respectively. They are fundamental to traffic flow, and are sometimes referred to ...
from that which is customary for the jurisdiction.
The crossovers may employ one-side overpasses or be at-grade and controlled by
traffic light
Traffic lights, traffic signals, or stoplights – known also as robots in South Africa are signalling devices positioned at intersection (road), road intersections, pedestrian crossings, and other locations in order to control flows of traf ...
.
The diverging diamond interchange has advantages in both efficiency and safety, and—despite having been in use in France since the 1970s—was cited by ''
Popular Science
''Popular Science'' (also known as ''PopSci'') is an American digital magazine carrying popular science content, which refers to articles for the general reader on science and technology subjects. ''Popular Science'' has won over 58 awards, incl ...
'' as one of the best engineering innovations of 2009 and in the U.S. has been promoted as part of the Federal Highway Administration's
Every Day Counts initiative. The flow through a diverging diamond interchange using overpasses at the crossovers is limited only by
weaving
Weaving is a method of textile production in which two distinct sets of yarns or threads are interlaced at right angles to form a fabric or cloth. Other methods are knitting, crocheting, felting, and braiding or plaiting. The longitudinal th ...
, 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.
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.
History
![Interstate 44 and Route 13 diverging diamond interchange](https://upload.wikimedia.org/wikipedia/commons/4/44/Interstate_44_and_Route_13_diverging_diamond_interchange.png)
The first known diverging diamond interchanges were in France in the communities of
Versailles
The Palace of Versailles ( ; french: Château de Versailles ) is a former royal residence built by King Louis XIV located in Versailles, about west of Paris, France. The palace is owned by the French Republic and since 1995 has been managed, u ...
(
A13 at D182),
Le Perreux-sur-Marne
Le Perreux-sur-Marne (, literally ''Le Perreux on Marne'') is a commune in the Val-de-Marne department in the eastern suburbs of Paris
Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 re ...
(
A4 at N486) and
Seclin
Seclin () is a commune in the Nord department in northern France. It is part of the Métropole Européenne de Lille.
Population
Notable residents
* Andre Ayew, Ghana national football team footballer
*Victor Mollet, architect
*Jonathan Roussel ...
(
A1 at D549), all built in the 1970s. The ramps of the first two have since been reconfigured to accommodate ramps of other interchanges, but they continue to function as diverging diamond interchanges. The interchange in Seclin (at ) between the
A1 and Route d'Avelin was 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.
In the United States in 2005, the
Ohio Department of Transportation
The Ohio Department of Transportation (ODOT; ) is the administrative department of the Ohio state government responsible for developing and maintaining all state and U.S. roadways outside of municipalities and all Interstates except the Ohio T ...
(ODOT) considered reconfiguring the existing interchange on
Interstate 75
Interstate 75 (I-75) is a major north–south Interstate Highway in the Great Lakes and Southeastern regions of the United States. As with most Interstates that end in 5, it is a major cross-country, north–south route, traveling from S ...
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. By 2006, ODOT had reconsidered, instead adding lanes to the existing overpass.
The
Missouri Department of Transportation
The Missouri Department of Transportation (MoDOT, ) is a state government organization in charge of maintaining public roadways of the U.S. state of Missouri under the guidance of the Missouri Highways and Transportation Commission. MoDOT designs, ...
was the first US agency to construct one, in
Springfield
Springfield may refer to:
* Springfield (toponym), the place name in general
Places and locations Australia
* Springfield, New South Wales (Central Coast)
* Springfield, New South Wales (Snowy Monaro Regional Council)
* Springfield, Queenslan ...
at the junction between
I-44
Interstate 44 (I-44) is a major Interstate Highway in the central United States. Although it is nominally an east–west road as it is even-numbered, it follows a more southwest–northeast alignment. Its western terminus is in Wichita Fa ...
and
Missouri Route 13
Route 13 is a highway in Missouri which runs almost the entire north–south length of the state. Its northern terminus is at U.S. Route 69/ 136 in Bethany. Its southern terminus is at the Arkansas state line in downtown Blue Eye, Misso ...
(at ). Construction began the week of January 12, 2009, and the interchange opened on June 21, 2009. This interchange was a conversion of an existing standard diamond interchange, and used the existing bridge.
In 2010, the
Federal Highway Administration
The Federal Highway Administration (FHWA) is a division of the United States Department of Transportation that specializes in highway transportation. The agency's major activities are grouped into two programs, the Federal-aid Highway Program a ...
released a publication titled "Alternative Intersections/Interchanges: Informational Report (AIIR)"
with a chapter dedicated to this design. Additional research was conducted by a partnership of the
Virginia Polytechnic Institute and State University
Virginia Tech (formally the Virginia Polytechnic Institute and State University and informally VT, or VPI) is a public land-grant research university with its main campus in Blacksburg, Virginia. It also has educational facilities in six regi ...
and the
Turner-Fairbank Highway Research Center Turner-Fairbank Highway Research Center is a U.S. Department of Transportation facility located in McLean, Virginia. The center carries out research studies and was renamed after Francis Turner in 1983. It had been known as the Fairbank Highway Re ...
and published by Ohio Section of the
Institute of Transportation Engineers
The Institute of Transportation Engineers (ITE) is an international educational and scientific association of transportation professionals who are responsible for meeting mobility and safety needs. ITE facilitates the application of technology and ...
.
In October 2016, the
New Mexico Department of Transportation
The New Mexico Department of Transportation (NMDOT; es, Departamento de Transporte de Nuevo México) is a state government organization which oversees transportation in New Mexico, State of New Mexico in the southwestern United States. The agency ...
completed the first diverging diamond interchange in
New Mexico
)
, population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano)
, seat = Santa Fe
, LargestCity = Albuquerque
, LargestMetro = Tiguex
, OfficialLang = None
, Languages = English, Spanish ( New Mexican), Navajo, Ker ...
. The interchange at
NM 14 (Cerrillos Road) and
Interstate 25
Interstate 25 (I-25) is a major Interstate Highway in the western United States. It is primarily a north–south highway, serving as the main route through New Mexico, Colorado, and Wyoming. I-25 stretches from I-10 at Las Cruces, New Mexic ...
in
Santa Fe was reconstructed to this interchange, and included replacement of aging overpasses carrying I-25 over NM 14 as well as adding traffic signals.
In November 2016, the
Delaware Department of Transportation
The Delaware Department of Transportation (DelDOT) is an agency of the U.S. state of Delaware. The Secretary of Transportation is Nicole Majeski. The agency was established in 1917 and has its headquarters in Dover.
The department's responsibil ...
completed the conversion of the
DE-1 and
DE-72 (Wrangle Hill Rd) overpass west of
Delaware City, DE
Delaware City is a city in New Castle County, Delaware, United States. The population was 1,695 at the 2010 census. It is a small port town on the eastern terminus of the Chesapeake and Delaware Canal and is the location of the Forts Ferry Cross ...
into a diverging diamond interchange.
The interchange is viewable via live traffic camera on th
DelDOT website
The first interchange in Canada opened on August 13, 2017, at
Macleod Trail
Macleod Trail is a major road in Calgary, Alberta. It is a six- to eight-lane principal arterial road extending from downtown Calgary to the south of the city, where it merges into Highway 2. South of Anderson Road, Macleod Trail is an expressw ...
and 162 Avenue South in
Calgary
Calgary ( ) is the largest city in the western Canadian province of Alberta and the largest metro area of the three Prairie Provinces. As of 2021, the city proper had a population of 1,306,784 and a metropolitan population of 1,481,806, makin ...
,
Alberta
Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...
followed by one in
Regina, Saskatchewan
Regina () is the capital city of the Provinces and territories of Canada, Canadian province of Saskatchewan. The city is the second-largest in the province, after Saskatoon, and is a commercial centre for southern Saskatchewan. As of the 2021 C ...
the next year as part of the
Regina Bypass
The Regina Bypass is a four-lane twinned highway connector road in Regina, Saskatchewan. The route connects Highway 1 (the Trans-Canada Highway) with Highway 11, forming a partial ring road around the city of Regina.
Phase on ...
project.
The first diverging diamond interchange in
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
opened to traffic by the
Queensland Department of Transport and Main Roads on November 28, 2019. The interchange, located in
Caloundra, Queensland
Caloundra ( ) is a coastal town and the southernmost town in the Sunshine Coast Region in South East Queensland, Australia.
Geography
Caloundra is north of the Brisbane central business district. Caloundra is accessible from Landsborough r ...
, connects Caloundra Road to the
Bruce Highway
The Bruce Highway is a major highway in Queensland, Australia. Commencing in the state capital, Brisbane, it passes through areas close to the eastern coast on its way to Cairns in Far North Queensland. The route is part of the Australian Na ...
. The former interchange was upgraded and converted as part of the larger Bruce Highway Upgrade Program.
In December 2019, the
Virginia Department of Transportation
The Virginia Department of Transportation (VDOT) is the agency of the state government responsible for transportation in the state of Virginia in the United States. VDOT is headquartered at the Virginia Department of Highways Building in downtown ...
completed the conversion of the interchange at Courthouse Road and I-95 in Stafford, VA into a diverging diamond interchange.
In 2020, the
California Department of Transportation
The California Department of Transportation (Caltrans) is an executive department of the U.S. state of California. The department is part of the cabinet-level California State Transportation Agency (CalSTA). Caltrans is headquartered in Sacrame ...
(Caltrans) completed the first diverging diamond interchange in
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
. An interchange at
State Route 120 and Union Road in
Manteca, California
Manteca (Spanish for "lard") is a city in San Joaquin County, California. The city had a population of 83,498 as of the 2020 census.
History
Manteca is a city in the Central Valley of California, located east of San Francisco. It was fou ...
was converted to this interchange and opened to traffic on November 25.
Use
Operational
, over 160 DDIs were operational across the world including:
* 3 in Australia with more planned
* 1 in Belgium
* 3 in Canada
* 1 in Denmark opened September 17, 2017
* 2 in France, built in 1970s
* 1 in Malaysia
* 2 in Saudi Arabia
* 2 in South Africa
* 1 in the United Arab Emirates
* 1 in Costa Rica
* Over 150 in the United States of America with 80 more under construction
Advantages
* Two-phase signals with short cycle lengths, significantly reducing delay.
* Reduced horizontal curvature reduces the risk of off-road crashes.
* Increases the capacity of turning movements to and from the ramps.
* Potentially reduces the number of lanes on the crossroad, minimizing space consumption.
* Reduces the number of conflict points, thus theoretically improving safety.
* Increases the capacity of an existing overpass or underpass, by removing the need for turn lanes.
* Costs significantly less than a normal interchange.
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.
* 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).
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.
* Highway bus stops must be sited outside the interchange.
* 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:
** Drivers who take the wrong exit
** Bypassing a crash at the bridge
** Allowing an
oversize load
In road transport, an oversize load (or overweight load) is a load that exceeds the standard or ordinary legal size and/or weight limits for a truck to convey on a specified portion of road, highway, or other transport infrastructure, such as a ...
to bypass a low bridge
Further considerations
* 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 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
![DCMI-Flow](https://upload.wikimedia.org/wikipedia/commons/2/24/DCMI-Flow.jpg)
A
free-flowing interchange variant, patented in 2015, has received recent attention.
Called the double crossover merging interchange (DCMI), it includes elements from the diverging diamond interchange, the
tight diamond interchange, and the
stack interchange
A directional interchange, colloquially known as a stack interchange, is a type of grade-separated junction between two controlled-access highways that allows for free-flowing movement to and from all directions of traffic. These interchanges e ...
. 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. As of 2016, no such interchanges have been constructed.
See also
*
List of road interchanges in the United States __NOTOC__
The following list contains the most notable road interchanges within the United States divided by each state, which are mainly part of the national Interstate Highway System and are all freeways intersecting with each other at a junction ...
*
Single-point urban interchange
A single-point urban interchange (SPUI, or ), also called a single-point interchange (SPI) or single-point diamond interchange (SPDI), is a type of highway interchange. The design was created in order to help move large volumes of traffic thro ...
(SPUI)
*
Jughandle
A jughandle is a type of ramp or slip road that changes the way traffic turns left at an at-grade intersection (in a country where traffic drives on the right). Instead of a standard left turn being made from the left lane, left-turning traffic ...
*
Hook turn
A hook turn (Australian English) or two-stage turn (British English), also known as a Copenhagen Left (in reference to cyclists specifically), is a road cycling manoeuvre or a motor vehicle traffic-control mechanism in which vehicles that would n ...
*
Michigan left
A Michigan left or P-turn is an at-grade intersection design that replaces each left (farside) turn at an intersection between a (major) divided roadway and a secondary (minor) roadway with the combination of a right (nearside) turn followe ...
*
Superstreet
A superstreet, also known as a restricted crossing U-turn (RCUT), J-turn, or reduced conflict intersection (RCI), is a type of road intersection that is a variation of the Michigan left. In this configuration, in contrast to the Michigan left, t ...
References
Further reading
*
*
*
*
External links
DDI Guideline – A UDOT Guide to Diverging Diamond Interchanges Utah Department of Transportation, June 2014
Transportation engineers discuss the design of the fifth U.S. DDI in Alcoa, TNVideo of Paramics Traffic Simualtion software modeling a Double Crossover Diamond InterchangeDiverging Diamond Interchange Visualization Instructional video on how to drive in a DDI, NCDOTcommunications, published on 10 March 2011
Images of Diverging Diamond Interchange in Springfield, Missourithe first in North America.
Animation of Diverging Diamond Interchange under construction at Elmhurst Road on Interstate 90 near Elk Grove, Illinois, to be completed in 2016Animation of Diverging Diamond Interchange at I-590/Winton Road (Rochester, New York)
Examples
* Diverging diamond in
Versailles
The Palace of Versailles ( ; french: Château de Versailles ) is a former royal residence built by King Louis XIV located in Versailles, about west of Paris, France. The palace is owned by the French Republic and since 1995 has been managed, u ...
, France
* Diverging diamond in
Seclin
Seclin () is a commune in the Nord department in northern France. It is part of the Métropole Européenne de Lille.
Population
Notable residents
* Andre Ayew, Ghana national football team footballer
*Victor Mollet, architect
*Jonathan Roussel ...
,
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
* Diverging diamond in
Springfield, Missouri
Springfield is the third largest city in the U.S. state of Missouri and the county seat of Greene County. The city's population was 169,176 at the 2020 census. It is the principal city of the Springfield metropolitan area, which had an estimat ...
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Road junction types
de:Anschlussstelle (Autobahn)#DDI / DCD