Single-point urban interchange

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Schematic of a freeway-under SPUI where traffic drives on the right. Traffic entering the freeway is in red. Traffic exiting the freeway is in green. Through traffic is in gray. All traffic motion of the same color can proceed simultaneously.

A single-point urban interchange (SPUI, /ˈsp/ or /ˈspjuː/), 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 through limited amounts of space safely and efficiently.


A typical freeway-over SPUI

A single point urban interchange is similar in form to a diamond interchange, but has the advantage of allowing opposing left turns to proceed simultaneously by compressing the two intersections of a diamond into one single intersection over or under the free-flowing road.[1]

The term "single point" refers to the fact that all through traffic on the arterial street, as well as the traffic turning left onto or off the interchange, can be controlled from a single set of traffic signals. Due to the space efficiency of SPUIs relative to the volume of traffic they can handle, the interchange design is being used extensively in the reconstruction of existing freeways as well as constructing new freeways, particularly in dense urban environments.[2]

Sometimes a SPUI will allow traffic to proceed straight through from the off-ramp to the on-ramp; this usually happens when the ramps connect with frontage roads. Since most through traffic travels over or under the intersection, the SPUI is still much more efficient than a surface intersection.


The first SPUI opened on February 25, 1974 along US 19 (SR 55), which goes over SR 60 east of Clearwater, Florida. It was designed by Wallace Hawkes, Director of Transportation Engineering at J.E. Greiner, Inc. (now URS Corporation), who has been called the "granddaddy of the urban interchange".[3][disputed ]


The most commonly cited advantages of single point urban interchanges are improved operation efficiency and safety as well as reduced right-of-way requirements compared to other interchange forms.[4] Left turning traffic from both directions of the intersecting roadways are able to turn simultaneously without crossing the path of the opposing left turns. Because traffic passing through the interchange can be controlled by a single signal, vehicles can clear the intersection much more quickly than in a diamond interchange (which requires two sets of traffic signals).

SPUIs also allow for wider turns, easing movement for large vehicles such as trucks and RVs. Furthermore, a SPUI takes up considerably less space than a full cloverleaf interchange, allowing construction to take place on a limited amount of property and minimizing state use of eminent domain.[5]

Finally, single point urban interchanges are reportedly safer than other space-efficient interchange forms such as (standard) diamond interchanges. Research suggests that, although there may not be a significant difference between the two types of interchanges in terms of total collisions, the injury and fatality rates are notably lower for SPUIs than diamond interchanges.[6]


The major disadvantage of single point urban interchanges over other types of road junctions is the increased cost due to the need for a longer or wider bridge. A freeway-under SPUI (as in the upper diagram) requires a wider bridge over the free-flowing road to make room for the compressed on- and off-ramps. However, this disadvantage poses less of a problem in cases where the arterial, or non-freeway road already requires a very wide bridge. The intersection of 97 Street, having seven through lanes, with Yellowhead Trail in Edmonton, Alberta, Canada, though a diamond interchange in concept, required such a wide bridge that traffic-signal phasing allows this intersection to behave as a SPUI.53°34′53″N 113°29′31″W / 53.58139°N 113.49194°W / 53.58139; -113.49194 (SPUI Edmonton) A freeway-over SPUI (as in the lower photo) requires a longer bridge of the free-flowing road to cross the wider area required for the SPUI intersection below.[3]

Additionally, because vehicles must be able to cross the pavement in six different ways, a SPUI generally has a very large area of uncontrolled pavement in the middle of the intersection. This can be unsafe particularly if drivers are unfamiliar with the interchange type. Drivers making a left turn may become confused as oncoming turning traffic passes them on the right-hand side (or left-hand side in countries that drive on the left).[3]

Also, due to the large intersection area, the traffic lights need a longer yellow and red phase to clear the intersection, and even then it may not be long enough for a bicyclist entering on green or yellow to make it across before opposing traffic gets a green.[4] In general, SPUI designs should not be used where bicycle traffic is expected unless fairly substantial changes to the design or special accommodations are provided.[7]

Pedestrians are usually not able to get through the intersection with one green light. It can take up to four cycles to walk through the entire length of a SPUI.[7]

Finally, SPUIs can be somewhat difficult to clear of snow. The large area in which lanes cross may have to be shut down to allow efficient and thorough cleaning lest a snowplow leave piles of snow, interfering with traffic and visibility in the middle of the uncontrolled pavement. Additionally, if the wide area of uncontrolled pavement is on a bridge, as in the diagram, the snow cannot be pushed to the sides of the bridge as it may pose a hazard to the road underneath. This problem can be exacerbated by the comparatively large bridge width required by the SPUI.

Three-phase traffic signals are required. Other interchange types designed for efficiency, such as the six ramp parclo and the diverging diamond, require just two signal phases.

Inverted SPUI[edit]

Inverted SPUI where traffic drives on the right. Ramps are located between carriageways.

A rarely built variant of the SPUI is the inverted SPUI, in which the carriageways of the free-flowing road are separated, with left on- and off-ramps running between the carriageways and coming to a single at-grade intersection with the cross street. This can be built less expensively than a standard SPUI by allowing for shorter, simpler bridges at the interchange. An inverted SPUI in Greensboro, North Carolina connects West Wendover Avenue to South Holden Road at 36°03′53″N 79°50′53″W / 36.064781°N 79.848098°W / 36.064781; -79.848098.[8]

On Interstate 244 in Tulsa, Oklahoma are inverted SPUIs at Sheridan Road 36°09′48″N 95°54′16″W / 36.163289°N 95.904535°W / 36.163289; -95.904535 and Memorial Drive 36°09′44″N 95°53′13″W / 36.16234°N 95.886873°W / 36.16234; -95.886873. On Interstate 290 in Chicago, Illinois at South Harlem Avenue 41°52′25″N 87°48′16″W / 41.873635°N 87.804505°W / 41.873635; -87.804505.[9]

A three-arm inverted SPUI is in Pultney Township, Belmont County, Ohio, between Bellaire and Bridgeport on State Route 7 at 40°02′52″N 80°44′01″W / 40.047657°N 80.733542°W / 40.047657; -80.733542. Only the southbound carriageway of SR 7 bridges over them, while SR 7's northbound carriageway remains at-grade. A similar design used in a three-arm inverted SPUI of at-grade freeflowing traffic can be found in a seagull intersection. The cross street of this inverted SPUI are ending at a trumpet interchange on Interstate 470. SR 7's left on- and off-ramps run between its carriageways, meeting I-470's ramps at an at-grade intersection. I-470 itself bridges over both carriageways of SR 7 a short distance north of the ramps' intersection. This design was likely chosen not for cost savings, but because the northbound carriageway of SR 7 is bordered by railroad tracks, commercial properties and the Ohio River, and because I-470 bridges the river just east of SR 7 – a more conventional interchange design was likely more difficult to achieve.

Use in North America[edit]

The first SPUI in Clearwater, Florida



In Edmonton are three SPUIs along the Trans-Canada Highway 16 (Yellowhead Highway) located at 97 St NW: 53°34′53″N 113°29′32″W / 53.581468°N 113.492151°W / 53.581468; -113.492151, 82 St NW: 53°34′56″N 113°28′02″W / 53.582296°N 113.467185°W / 53.582296; -113.467185 and Fort Rd NW: 53°34′50″N 113°27′11″W / 53.580589°N 113.453055°W / 53.580589; -113.453055.

City of Calgary has a SPUI at MacLeod Trail to Glenmore Trail, 50°59′39″N 114°04′18″W / 50.994264°N 114.071551°W / 50.994264; -114.071551.


In Winnipeg there is a proposed SPUI at Marion Street and Archibald Street.


In Ontario there are two SPUIs. One is located on the Airport Parkway (Ottawa Road 79) in Ottawa at the Hunt Club Road (Ottawa Road 32) interchange. 45°21′01″N 75°39′18″W / 45.350213°N 75.654933°W / 45.350213; -75.654933 The other is on Highway 406 at the Fourth Avenue (Niagara Regional Road 77) interchange in St. Catharines. 43°09′27″N 79°15′35″W / 43.157376°N 79.259735°W / 43.157376; -79.259735

United States[edit]


In Huntsville there are four SPUIs on Memorial Parkway SW.


In Fairbanks there are two SPUIs on the Johansen Expressway, one at the junction with College Road and the other at the junction with Peger Road. A modified SPUI exists at the intersection of the George Parks Highway, Seward Meridian Parkway and Fireweed Road in Wasilla.


  • Tucson metropolitan area:
    • On Interstate 19 there is a SPUI at the West Valencia Road interchange.
    • On I-19 a SPUI is planned on Ajo Way.[10]
    • State Route 210 (Barraza-Aviation Parkway) meets Kino Parkway at a SPUI.
  • Phoenix metropolitan area:
    • On Interstate 10 in Phoenix there are two SPUIs: one at the North 7th Street interchange and one at the North 7th Avenue interchange.
    • On Interstate 17 in Phoenix there are a total of five SPUIs at the following crossroads: West Dunlap Avenue, West Northern Avenue, West Glendale Avenue, West Bethany Home Road and West Camelback Road.
    • There are several SPUIs on State Route 51 in Phoenix at the following crossroads with the freeway: East McDowell Road, East Thomas Road, East Indian School Road, a modified SPUI at East Bethany Home Road, East Glendale Avenue, East Shea Boulevard, East Cactus Road, East Greenway Road, East Bell Road and East Union Hills Drive.
    • On State Route 202 in Tempe there is a single SPUI with North Scottsdale Road and in Phoenix there are three SPUIs at these crossroads: North 44th Street, North 32nd Street and North 24th Street.
    • In the short length of State Route 143 there are two SPUIs: one at the junction with East Washington Street and the other at the junction with West University Drive.
    • On State Route 101 there is an extensive number of SPUIs; starting at the junction with State Route 202 the SPUI interchange list goes as follows: East Guadalupe Road, North Pima Road, East Shea Boulevard, East Cactus Road, East Raintree Drive, North Frank Lloyd Wright Boulevard, North Tatum Boulevard, North Cave Creek Road, West Bell Road, West Glendale Avenue and West Camelback Road.



  • Intersection of SH-470 and SH-8 (Morrison Road) in Morrison. Another exists at the intersection of US-85 (Santa Fe Drive) and Evans Avenue in Denver. This SPUI was necessitated by a multi-track rail corridor directly to the east of Santa Fe Drive. Another SPUI exists at University Boulevard and Interstate 25 in Central Denver.



The first SPUI in the US was built near Clearwater in 1974. It is located where US 19 crosses State Road 60. There are several others in the state, including one at the eastern terminus of the Beachline Expressway at State Road 401. The Florida Department of Transportation during their ongoing US 19 reconstruction work has also been incorporating them in the newly constructed areas.

On the east side of Jacksonville, several SPUIs have been built on I-295 and on Butler Boulevard.


SPUIs are used at these junctions in metro Atlanta (freeway route listed first):


  • I-84 and S. Vista Ave (exit 53) in Boise, and at the intersection of Ten Mile Road and I-84 (exit 42) in Meridian.[12] SPUI interchanges are under construction at I-84 and Broadway Ave. (exit 54) in Boise, and at I-84 and Meridian Rd./SH 69 (exit 44) in Meridian.


The Stevenson Expressway (I-55) in Chicago features three SPUIs: at Central Avenue (Exit 285), Pulaski Road (Exit 287), and Damen Avenue (Exit 290). The SPUI design is well-suited as an upgrade to original diamond interchanges on this road, which was built on a narrow strip of land sandwiched between the Chicago Sanitary and Ship Canal and railroad tracks. There is a SPUI at the junction of I-80/I-94 (Kingery Expressway) and US 6/IL 83 (Torrence Avenue) in Lansing and another SPUI at the junction of US 20 (Elgin Bypass / Dr. Martin Luther King Jr. Memorial Highway) and South McLean Boulevard in Elgin.





  • I-75 and SH92 at Williamsburg in southern Kentucky. There are nine total in Kentucky with one under construction.


  • I-695 and MD-140 in Pikesville
  • I-70 and MD-85/East St. in Frederick
  • I-270 and Falls Rd. in Rockville
  • MD-100 and MD-170/Telegraph Rd. in Severn
  • US-29 and Randolph Rd./Cherry Hill Rd.

There are three SPUI interchanges on MD-5 at MD-337/Allentown Road, Coventry Way, and MD-223/Woodyard Road[18]


SPUIs are in use at the Beck Road and Wixom Road exits of I-96 in Novi; the Westnedge Avenue exit of I-94 in Portage; the Telegraph Road exit of I-94 in Taylor (at 42°15′54″N 83°16′14″W / 42.264924°N 83.270425°W / 42.264924; -83.270425), east of the Detroit Metropolitan Wayne County Airport; the Kalamazoo Avenue interchange on M-6; and the M-59 exit of US 23 in Hartland.[19]



New Hampshire[edit]

The first SPUI in New Hampshire was constructed at the interchange where New Hampshire Route 108 crosses NH 101 at exit 11 in Stratham. Other locations include:

New Jersey[edit]

A modified SPUI opened in 2001 within the reconstructed intersection of US 1, US 130, and Route 171 in North Brunswick.[21] (40°27′40″N 74°27′18″W / 40.461°N 74.455°W / 40.461; -74.455)

The first conventional SPUI opened in 2013 at the New Jersey Turnpike's relocated Interchange 8 and Routes 33 and 133.[22] (40°16′08″N 74°30′00″W / 40.269°N 74.500°W / 40.269; -74.500)

New Mexico[edit]

Two SPUIs are located in the Albuquerque metropolitan area: the I-40 Exit 162 interchange at Louisiana Boulevard (35°05′51″N 106°34′07″W / 35.097572°N 106.568729°W / 35.097572; -106.568729), and the interchange between Coors Road (NM 448) and Paseo del Norte (NM 423) (35°10′51″N 106°40′05″W / 35.180939°N 106.668099°W / 35.180939; -106.668099).

Also in Albuquerque, a modified SPUI is used at the interchange of Paseo del Norte and 2nd Street NW (35°10′40″N 106°37′21″W / 35.177881°N 106.622373°W / 35.177881; -106.622373). Another modified SPUI is under construction as a replacement for the intersection of Paseo del Norte and Jefferson Street NE (35°10′28″N 106°35′36″W / 35.174443°N 106.593437°W / 35.174443; -106.593437), as part of a larger project to improve the nearby interchange between I-25 and Paseo del Norte.[23]

The I-25 Exit 242 interchange with US 550 and NM 165 near Bernalillo (35°18′58″N 106°32′02″W / 35.316192°N 106.533914°W / 35.316192; -106.533914) was rebuilt in a SPUI layout in the spring of 2014.

The only SPUI interchange outside of Albuquerque is the interchange of US 84/285 and NM 502 in Pojoaque.

New York[edit]

The first single-point urban interchange (SPUI) in New York State is in Centereach between State Route 25 and CR 97 – Stony Brook, Blue Point [24]

A SPUI replaced the previous interchange between I-87 and State Route 7 (Troy-Schenectady Road), Exit 6, in Latham.[25] (42°45′11″N 73°46′08″W / 42.753126°N 73.76897°W / 42.753126; -73.76897)

North Carolina[edit]

  • I-77 at Tyvola Road (exit 5) in Charlotte
  • I-85 at NC 27 (Freedom Drive, exit 34), and at NC 16 (Brookshire Boulevard, exit 36), both in Charlotte
  • I-540 at Six Forks Road (exit 11) just north of Raleigh
  • Exit 276 (Fayetteville Street) off I-40 in Durham

With the widening of I-40 in Greensboro in the 2000s, a new interchange was built at Gallimore Dairy Road. Space was limited by the adjoining tank farms, so a SPUI was built.



A second SPUI at the junction of I-35 and W. Main St. in Norman 35°13′07″N 97°29′08″W / 35.218557°N 97.485521°W / 35.218557; -97.485521 is open as of April 2014.


  • South Medford exit on I-5 (Exit 27).

South Carolina[edit]

South Dakota[edit]

Several SPUIs serve the freeway system around Sioux Falls. Exit 6 of I-229 on SD-42 (10th Street)/Downtown was the first in the city. The newest is at exit 399 of I-90 on SD-115 (Cliff Avenue)/Renner. I-29 contains four SPUIs (from north to south): exit 82 (Benson Road), exit 80 (Madison Street/Ellis), exit 79 (SD-42 (12th Street)/Downtown), and exit 73 (Tea/101st Street/future SD-100).

Four SPUIs are found in Rapid City. Exit 58 from I-90 at N Haines Ave/5th Street was the first in the city. Exit 60 from I-90 at East North Street was second. Two more were added with the completion of the southeast city bypass at Exit 61 from I-90 at Elk Vale, and at the junction of SD-79 and East Catron Blvd/Elk Vale Rd.



I-15 at 600 North in Salt Lake City

Utah uses several SPUIs on I-15 along the Wasatch Front, with the first one at the SR-201 interchange at 3200 West being built in 1980.[26] Bangerter Highway (SR-154) is connected to I-15 with a SPUI in Draper at 40°30′15″N 111°53′29″W / 40.504206°N 111.891474°W / 40.504206; -111.891474, 7800 South to Bangerter at 40°36′34″N 111°58′36″W / 40.609497°N 111.976563°W / 40.609497; -111.976563 is SPUI in West Jordan.



Use in Asia[edit]

Hong Kong[edit]



Beside some diamond interchanges, there are SPUIs at Eunos Flyover at 1°19′34″N 103°54′21″E / 1.326191°N 103.905765°E / 1.326191; 103.905765, Loyang Flyover at 1°21′37″N 103°57′40″E / 1.360214°N 103.961109°E / 1.360214; 103.961109 and the Paya Lebar interchange at 1°19′22″N 103°53′27″E / 1.322866°N 103.890912°E / 1.322866; 103.890912.

Use in Europe[edit]


Several SPUIs, built in the 1970s and later, are located on Autobahns A 40, A 42, A 44, A 46, A 57, A 59 and A 113 in Berlin. There is also a SPUI on the Frankenschnellweg, the urban part of Autobahn A 73, and Maximilianstraße, in Nuremberg (at 49°27′06″N 11°02′17″E / 49.451708°N 11.038102°E / 49.451708; 11.038102). Smaller versions of the SPUI can also be found on non-autobahn roads in German cities, having right turning traffic under signal control, located in Heilbronn, Karlsruhe, Sindelfingen, Stuttgart and Wiesbaden.


See also[edit]


  1. ^ Anonymous (July 1989). "Urban interchange moves more traffic in same space; a design new to California improves congested diamond interchanges without taking more high-priced real estate". Highway & Heavy Construction 132 (8): 52–53. ISSN 0362-0506. 
  2. ^ St. Louis District. "Single Point Urban Interchanges". Missouri Department of Transportation. Retrieved July 15, 2012. 
  3. ^ a b c "Single-point Urban Interchange (SPUI)". Retrieved April 9, 2008. [unreliable source]
  4. ^ a b Bonneson, James A. (January 1993). "Bridge Size and Clearance Time of Single Point Urban Interchange". Journal of Transportation Engineering (American Society of Civil Engineers) 119 (1): 77–93. doi:10.1061/(ASCE)0733-947X(1993)119:1(77). ISSN 0733-947X. 
  5. ^ St. Louis District. "Single Point Urban Interchange Frequently Asked Questions". Missouri Department of Transportation. Retrieved July 15, 2012. 
  6. ^ Bared, Joe; Powell, Alvin; Kaisar, Evangelos; Jagannathan, Ramanujan (May 2005). "Crash Comparison of Single Point and Tight Diamond Interchanges". Journal of Transportation Engineering (American Society of Civil Engineers) 131 (5): 379–381. doi:10.1061/(ASCE)0733-947X(2005)131:5(379). ISSN 0733-947X. 
  7. ^ a b Qureshi, Mohammad; Sugathan, Navin; Lasod, Rohit; Spring, Gary (September 2004). "Design of Single Point Urban Interchanges, Research Investigation 02-015" (PDF). Missouri Department of Transportation Research, Development, and Technology, University of Missouri-Rolla. Retrieved February 10, 2010. 
  8. ^ Jonathan Reid, P.E. (July 2004). "Unconventional arterial intersection design, management and operations strategies" (PDF). Parsons Brinckerhoff. Retrieved September 9, 2012. 
  9. ^ Single-point Urban Interchange (SPUI), aka Single-Point Diamond. Retrieved November 30, 2013[unreliable source]
  10. ^ "Overview". Retrieved February 1, 2014. 
  11. ^,-117.5936832,423m/data=!3m1!1e3
  12. ^ "Idaho’s First SPUI – I-84 Vista Interchange". Stanley Consultants. Retrieved July 31, 2013. 
  13. ^ "[INDOT] Allisonville Road Bridge Over I-465 Opens to Traffic - 9/24/2012 - IN.GOV". Retrieved February 1, 2014. 
  14. ^ "[INDOT] Allisonville Road Project Open House - 5/17/2012 - IN.GOV". Retrieved February 1, 2014. 
  15. ^
  16. ^
  17. ^
  18. ^,-76.899745&sspn=0.121012,0.308647&ie=UTF8&t=h&z=12
  19. ^ Michigan Department of Transportation. "US-23/M-59 opens; SPUI introduced in Livingston County". Michigan Department of Transportation. Retrieved September 26, 2013. 
  20. ^ "MoDOT Kansas City Area District News Release". Retrieved 2014-04-02. 
  21. ^ "Award-Winning Solutions - U.S. Route 1/U.S. Route 130/Route 171 Interchange". Gannett Fleming. Retrieved February 3, 2014. In addition, a frontage road, forming New Jersey’s first single point urban interchange, ... 
  22. ^ Morgan, Jamie. "New Jersey Turnpike Authority". Construction Today. Retrieved February 3, 2014. 
  23. ^  Missing or empty |title= (help)
  24. ^ Anderson, Steve. "Nicolls Road". NYCRoads. Retrieved March 18, 2010. 
  25. ^ "The Latham SPUI now has its own website". September 17, 2008. 
  26. ^ Brown, Matthew (January 20, 1991). "Resist Impulse to Say 'Phooey' to the Safe and Efficient 'SPUI'". Deseret News. OCLC 10171976. Retrieved January 24, 2014. 

External links[edit]