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 through limited amounts of space safely and efficiently.
- 1 Overview
- 2 Advantages
- 3 Disadvantages
- 4 Use in North America
- 4.1 Canada
- 4.2 United States of America
- 4.2.1 Alabama
- 4.2.2 Alaska
- 4.2.3 Arizona
- 4.2.4 California
- 4.2.5 Colorado
- 4.2.6 Connecticut
- 4.2.7 Florida
- 4.2.8 Georgia
- 4.2.9 Idaho
- 4.2.10 Illinois
- 4.2.11 Indiana
- 4.2.12 Iowa
- 4.2.13 Kansas
- 4.2.14 Kentucky
- 4.2.15 Maryland
- 4.2.16 Michigan
- 4.2.17 Minnesota
- 4.2.18 Missouri
- 4.2.19 New Hampshire
- 4.2.20 New Jersey
- 4.2.21 New Mexico
- 4.2.22 New York
- 4.2.23 North Carolina
- 4.2.24 Ohio
- 4.2.25 Oklahoma
- 4.2.26 Oregon
- 4.2.27 South Carolina
- 4.2.28 South Dakota
- 4.2.29 Tennessee
- 4.2.30 Utah
- 4.2.31 Virginia
- 4.2.32 Washington
- 5 Use in Asia
- 6 Use in Europe
- 7 Inverted SPUI
- 8 See also
- 9 References
- 10 External links
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.
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.
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".[disputed ]
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 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. 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.
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.
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. 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.
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).
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. 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.
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.
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.
Use in North America
City of Calgary has a SPUI at MacLeod Trail to Glenmore Trail, .
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. The other is on Highway 406 at the Fourth Avenue (Niagara Regional Road 77) interchange in St. Catharines.
United States of America
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:
- 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.
A SPUI exists at the 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.
The first SPUI in the U.S. 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.
SPUIs are used at these junctions in metro Atlanta (freeway route listed first):
- SR 400 at SR 141 Connector (Lenox Road NE, exit 2)
- Several junctions along SR 141 (Peachtree Industrial Boulevard). These SPUIs also involve frontage roads.
- Tilly Mill Road
- Winters Chapel Road
- SR 140 (Jimmy Carter Boulevard)
- Sugarloaf Parkway at New Hope Road, near Lawrenceville
There is a SPUI at the junction of I-84 and S. Vista Ave in Boise, and at the intersection of Ten Mile Road and I-84 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.
There is a SPUI at the junction of I-75 and SH92 at Williamsburg in Southern Kentucky. There are nine total in Kentucky with one under construction.
There is a SPUI at the junction of I-695 and MD-140 in Pikesville.
There is a SPUI at the junction of I-70 and MD-85/East St. in Frederick.
There is a SPUI at the junction of I-270 and Falls Rd. in Rockville.
There is a SPUI at the junction of MD-100 and MD-170/Telegraph Rd. in Severn.
There is a SPUI at the junction of 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
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 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.
Also in Albuquerque, a modified SPUI is used at the interchange of Paseo del Norte and 2nd Street NW (under construction as a replacement for the intersection of Paseo del Norte and Jefferson Street NE ( ), as part of a larger project to improve the nearby interchange between I-25 and Paseo del Norte.). Another modified SPUI is
SPUIs are found in several locations in the state, including:
- 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 had a SPUI open in 2002.
There is a SPUI at the South Medford exit on I-5 (Exit 27).
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).
On State Route 385 at Tennessee State Route 175 in Collierville.
On State Route 385 at South Houston Levee Road in Collierville.
On State Route 385 at Forest Hill Irene Road in Collierville.
On State Route 385 at Riverdale Road in Memphis.
On State Route 385 at Kirby Parkway in Memphis.
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. Bangerter Highway (SR-154) is connected to I-15 with a SPUI in Draper at , 7800 South to Bangerter at is SPUI in West Jordan.
A third SPUI at I-405 and NE 116th Street (at ) was completed in 2012. This particular junction only serves traffic coming/going south on I-405.
Use in Asia
Beside some diamond interchanges, there are SPUIs at Eunos Flyover at, Loyang Flyover at and the Paya Lebar interchange at .
Use in Europe
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 ). 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.
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 .
A three-arm inverted SPUI is in Pultney Township, Belmont County, Ohio, between Bellaire and Bridgeport on State Route 7 at . 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.
- 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.
- St. Louis District. "Single Point Urban Interchanges". Missouri Department of Transportation. Retrieved July 15, 2012.
- "Single-point Urban Interchange (SPUI)". Kurumi.com. Retrieved April 9, 2008.[unreliable source]
- 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.
- St. Louis District. "Single Point Urban Interchange Frequently Asked Questions". Missouri Department of Transportation. Retrieved July 15, 2012.
- 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.
- 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.
- "Overview". azdot.gov. Retrieved February 1, 2014.
- "Idaho’s First SPUI – I-84 Vista Interchange". Stanley Consultants. Retrieved July 31, 2013.
- "[INDOT] Allisonville Road Bridge Over I-465 Opens to Traffic - 9/24/2012 - IN.GOV". in.gov. Retrieved February 1, 2014.
- "[INDOT] Allisonville Road Project Open House - 5/17/2012 - IN.GOV". in.gov. Retrieved February 1, 2014.
- Michigan Department of Transportation. "US-23/M-59 opens; SPUI introduced in Livingston County". Michigan Department of Transportation. Retrieved September 26, 2013.
- "MoDOT Kansas City Area District News Release". modot.com. Retrieved 2014-04-02.
- "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, ..."
- Morgan, Jamie. "New Jersey Turnpike Authority". Construction Today. Retrieved February 3, 2014.
- http://www.paseoi25.com/Default.aspx. Missing or empty
- Anderson, Steve. "Nicolls Road". NYCRoads. Retrieved March 18, 2010.
- "The Latham SPUI now has its own website". September 17, 2008.
- Brown, Matthew (January 20, 1991). "Resist Impulse to Say 'Phooey' to the Safe and Efficient 'SPUI'". Deseret News. OCLC 10171976. Retrieved January 24, 2014.
- Jonathan Reid, P.E. (July 2004). "Unconventional arterial intersection design, management and operations strategies" (PDF). Parsons Brinckerhoff. Retrieved September 9, 2012.
- Single-point Urban Interchange (SPUI), aka Single-Point Diamond. Retrieved November 30, 2013[unreliable source]
|Wikimedia Commons has media related to Single-point urban interchanges.|
- Michigan Department of Transportation page about SPUIs
- Missouri Department of Transportation page about SPUIs
- Page about SPUIs at kurumi.com[unreliable source]