Continuous flow intersection
Encyclopedia
At-grade intersection
An at-grade intersection is a junction at which two or more transport axes cross at the same level .-Traffic management:With areas of high or fast traffic, an at-grade intersection normally requires a traffic control device such as a stop sign, traffic light or railway signal to manage conflicting...
that moves the turning vehicles, conflicting with the through-movements (to the left where traffic drives on the right, and vice-versa), out of the main intersection
Intersection (road)
An intersection is a road junction where two or more roads either meet or cross at grade . An intersection may be 3-way - a T junction or fork, 4-way - a crossroads, or 5-way or more...
. A CFI moves the left turn down the road several hundred feet, eliminating the left-turn traffic signal
Traffic light
Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signalling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic...
phase. A fly-over designed CFI (non-at-grade) was a previously patented design invented by Francisco Mier, of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
. Over 40 have been implemented over the past decade. As the design was patented, agencies previously had to pay to obtain the rights for use of the design; however, the patent has expired in the United States. This general configuration has appeared in different versions in various places, with the implementation of channelization
Channelization (roads)
Channelization is an engineering concept which employs the use of secondary roads to separate certain flows of traffic from the main traffic lanes. This method came into favor in the United States in the 1950s.-References:...
in the United States since the 1950s, such as the Telegraph Road section of U.S. Route 24 in Michigan.
CFI locations in the United States
Listed in order of implementation:- Haddon Township, New JerseyHaddon Township, New JerseyHaddon Township is a Township in Camden County, New Jersey, United States. As of the United States 2010 Census, the township population was 14,707....
and Audubon Park, New JerseyAudubon Park, New JerseyAudubon Park is a Borough in Camden County, New Jersey, United States. As of the 2010 United States Census, the borough population was 1,023.Audubon Park was incorporated as a borough on July 3, 1947, from portions of Audubon Borough, based on the results of a referendum held on October 28, 1947,...
, New Jersey Route 168 at Nicholson Road, is a hybrid continuous flow intersection that also employs a jughandleJughandleA jughandle is a type of ramp or slip road that changes the way traffic turns left at at-grade intersections. Instead of a standard left turn being made from the left lane, left-turning traffic uses a ramp on the right side of the road...
. (A nearby intersection on New Jersey Route 168 at US Highway 130 in Haddon Township, New JerseyHaddon Township, New JerseyHaddon Township is a Township in Camden County, New Jersey, United States. As of the United States 2010 Census, the township population was 14,707....
and Camden, New JerseyCamden, New JerseyThe city of Camden is the county seat of Camden County, New Jersey. It is located across the Delaware River from Philadelphia, Pennsylvania. As of the 2010 United States Census, the city had a total population of 77,344...
resembles a Parallel Flow Intersection, or PFI). - Shirley, New YorkShirley, New YorkShirley is a hamlet in Suffolk County, New York, United States. As of the 2000 census, Shirley population was 26,395....
, opened in 1996, at the entrance to Dowling CollegeDowling CollegeDowling College is a private co-educational liberal arts college with three campuses spread across Long Island, New York. The college's main campus in Oakdale, NY sits on the site of William K. Vanderbilt's former Idle Hour estate, which is now known as Fortunoff Hall. The Brookhaven Campus in...
. - Accokeek, MarylandAccokeek, MarylandAccokeek is an unincorporated area and census-designated place in Prince George's County, Maryland, United States, located about 8.5 miles southwest of Washington, D.C. The population was 7,349 at the 2000 census. It is home to Piscataway Park....
, opened in 2000, at the intersection of Routes 210Maryland Route 210Maryland Route 210 , or Indian Head Highway, is a state highway in Prince George's and Charles counties in Maryland. At its northern end, MD 210 starts from the end of South Capitol Street in Washington, D.C., connecting the U.S. Capitol with Indian Head, Maryland...
and 228Maryland Route 228Maryland Route 228 is a state highway in the U.S. state of Maryland. Known as Berry Road, the state highway runs from MD 210 in Accokeek east to U.S. Route 301 and MD 5 Business in Waldorf...
. - Baton Rouge, LouisianaBaton Rouge, LouisianaBaton Rouge is the capital of the U.S. state of Louisiana. It is located in East Baton Rouge Parish and is the second-largest city in the state.Baton Rouge is a major industrial, petrochemical, medical, and research center of the American South...
, opened in March 2006, at the intersection of Airline Hwy and Siegen Lane. - West Valley City, UtahWest Valley City, UtahWest Valley City is a city in Salt Lake County and a suburb of Salt Lake City in the U.S. state of Utah. The population was 129,480 at the 2010 census,...
, opened in September 2007, at the intersections of Bangerter Highway and 5300 South (SR 173), 4700 South, 4100 South, and 3500 South - Fenton, MissouriFenton, MissouriFenton is a city in St. Louis County, Missouri, United States, and a suburb of St. Louis. The population was 4,022 at the 2010 census.-History:Due to its proximity to fertile land and the Meramec River, the Fenton area has been inhabited for over 1,000 years...
, opened October 2007, at the intersection of Highway 30 and Summit Drive/Gravois Bluffs Blvd. - Miami Township, OhioMiami Township, OhioMiami Township, Ohio may refer to:*Miami Township, Clermont County, Ohio*Miami Township, Greene County, Ohio*Miami Township, Hamilton County, Ohio*Miami Township, Logan County, Ohio*Miami Township, Montgomery County, Ohio...
, construction spring of 2009, at intersection of SR 741 and Miamisburg-Springboro Road/ Austin Pike. - Salt Lake County, UtahSalt Lake County, UtahSalt Lake County is a county located in the U.S. state of Utah. It had a population of 1,029,655 at the 2010 census. Its county seat and largest city is Salt Lake City, the state capital. It occupies Salt Lake Valley, as well as parts of the surrounding mountains, the Oquirrh Mountains to the west...
, announced October 2009, the Utah Department of Transportation revealed plans for five more continuous flow intersections along Bangerter Highway and Redwood Road. As of March 11, 2011, four of them are now open. - Natchez, MississippiNatchez, MississippiNatchez is the county seat of Adams County, Mississippi, United States. With a total population of 18,464 , it is the largest community and the only incorporated municipality within Adams County...
, opened January 2010 at the intersection of US 61 and Junkin Drive, designed by ABMB Engineers and constructed by MDOT - Lafayette, LouisianaLafayette, LouisianaLafayette is a city in and the parish seat of Lafayette Parish, Louisiana, United States, on the Vermilion River. The population was 120,623 at the 2010 census...
, ground broke January 2010 at the intersection of US 167 (Johnston St.) and Camellia Boulevard. Estimated cost of $3.5 Million. - Loveland, ColoradoLoveland, ColoradoLoveland is a Home Rule Municipality that is the second most populous city in Larimer County, Colorado, United States. Loveland is situated north of the Colorado State Capitol in Denver. Loveland is the 14th most populous city in Colorado. The United States Census Bureau that in 2010 the...
, ground broke June 2010 at the intersection of US 34 (Eisenhower Blvd.) and Madison Ave. Estimated cost of $4 Million. - Orem, UtahOrem, UtahOrem is a city in Utah County, Utah, United States, in the north-central part of the state. It is adjacent to Provo, Lindon, and Vineyard and is about south of Salt Lake City. Orem is one of the principal cities of the Provo-Orem, Utah Metropolitan Statistical Area, which includes all of Utah and...
, construction began April 2010 (expected completion of December 2012) on the I-15 CORE project which includes the redesign of the University Parkway and Sandhill Road intersection into a continuous flow intersection.
Operational details
In the diagram to the right, while the east/west traffic is flowing through the intersection, the north/south left-turn traffic is allowed through each of the smaller intersections that are a few hundred feet from the main intersection. When the north/south through traffic is allowed through the main intersection, the north/south left-turn lanes are also allowed through the intersections. All traffic flow is controlled by traffic signals as at a regular intersection.
The Louisiana DOTD article on the Baton Rouge CFI includes a particularly informative diagram of that intersection.
To reduce confusion regarding the left-turn lane, the left-turn lane and the straight-through lanes are usually separated by a concrete barrier
Jersey barrier
A Jersey barrier or Jersey wall is a modular concrete barrier employed to separate lanes of traffic. It is designed to both minimize vehicle damage in cases of incidental contact while still preventing crossover in the case of head-on accidents....
or traffic island
Traffic island
A traffic island is a solid or painted object in a road that channelises traffic. It can also be a narrow strip of island between roads that intersect at an acute angle. If the island uses road markings only, without raised kerbs or other physical obstructions, it is called a painted island...
. This diagram shows the straight-through lanes offset by one lane through the intersection and are guided by lines painted through the intersection. But this is just a sample configuration; the lanes may be offset by more lanes or none at all.
Nonetheless, due to the provision of traffic between two directions of opposing traffic, some motorists tend to maintain an ongoing criticism of the intersection. Additionally, as in the case of the half-CFI in Accokeek, the offset left-turn traffic reenters the main traffic stream via a half-signal, requiring motorists to merge from a stop condition onto the higher-speed mainline. Motorists sometimes cite discomfort due to the speed differential, a known cause of accidents, though conflicts could be reduced through the provision of an adequate acceleration lane and merge area. The Accokeek, MD CFI also has notable inequalities in traffic flow depending upon the direction of travel.
This type of intersection can require a significant amount of right-of-way to implement (dependent upon the configuration), which is why the technique is not frequently used in urban areas. However, the amount of right-of-way necessary for construction and final operation is still typically less than that of an interchange. Additionally, as there is no grade separation involved, costs are considerably less than that of an interchange alternative.
See Also
- Diverging diamond interchangeDiverging diamond interchangeA 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 to briefly drive on the...
- Double Crossover Merging InterchangeDouble Crossover Merging InterchangeA Double Crossover Merging Interchange is a new type of interchange. The traffic lane patterns lane of the DCMI’s offers a system of creating a high volume interchange that allows traffic to continuously flow without the need for costly elevated “fly-over” roadway bridges, and uses less lane area...
- JughandleJughandleA jughandle is a type of ramp or slip road that changes the way traffic turns left at at-grade intersections. Instead of a standard left turn being made from the left lane, left-turning traffic uses a ramp on the right side of the road...
- Hook turnHook turnA hook turn is a traffic-control mechanism where cars that would normally have to turn across oncoming traffic are made to turn across all lanes of traffic instead....
- Michigan leftMichigan leftA Michigan left is an at-grade intersection design which replaces each left turn with a permutation of a U-turn and a right turn. The design was given the name due to its frequent use along Michigan roads and highways since the late 1960s. In other contexts, the intersection is called a median...
- SuperstreetSuperstreetA superstreet is a type of road intersection that is a variation of the Michigan left. In this configuration, traffic on the minor road is not permitted to proceed straight across the major road or highway; traffic wishing to turn left or go straight must turn right onto the major road, make a...
External links
- Federal Highway AdministrationFederal Highway AdministrationThe Federal Highway Administration 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 and the Federal Lands Highway Program...
, Alternative Intersection Treatments - CFI - University of MarylandUniversity of Maryland, College ParkThe University of Maryland, College Park is a top-ranked public research university located in the city of College Park in Prince George's County, Maryland, just outside Washington, D.C...
, ATTAP - Animation of a CFI (Quicktime required). Additional information may be accessed via the links on the left side.
Location of a CFI in Oaklyn, New Jersey, USA
Oaklyn, New Jersey
Oaklyn is a Borough in Camden County, New Jersey, United States. As of the 2010 United States Census, the borough population was 4,038.Oaklyn was incorporated as a borough by an Act of the New Jersey Legislature on March 13, 1905, from portions of Haddon Township.-Geography:Oaklyn is located at ...
Location of a CFI in Shirley, New York, USA
Shirley, New York
Shirley is a hamlet in Suffolk County, New York, United States. As of the 2000 census, Shirley population was 26,395....
Location of a CFI in Accokeek, Maryland, USA
Accokeek, Maryland
Accokeek is an unincorporated area and census-designated place in Prince George's County, Maryland, United States, located about 8.5 miles southwest of Washington, D.C. The population was 7,349 at the 2000 census. It is home to Piscataway Park....
Location of a CFI in Baton Rouge, Louisiana, USA
Baton Rouge, Louisiana
Baton Rouge is the capital of the U.S. state of Louisiana. It is located in East Baton Rouge Parish and is the second-largest city in the state.Baton Rouge is a major industrial, petrochemical, medical, and research center of the American South...
Location of a CFI in West Valley City, Utah, USA
West Valley City, Utah
West Valley City is a city in Salt Lake County and a suburb of Salt Lake City in the U.S. state of Utah. The population was 129,480 at the 2010 census,...
Location of a CFI in Fenton, Missouri, USA
Fenton, Missouri
Fenton is a city in St. Louis County, Missouri, United States, and a suburb of St. Louis. The population was 4,022 at the 2010 census.-History:Due to its proximity to fertile land and the Meramec River, the Fenton area has been inhabited for over 1,000 years...
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- Note that due to the relatively recent installation of the CFI in Baton Rouge, West Valley, UT, and Fenton, MO, some images may not show the existing conditions.