Cloverleaf interchange
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A cloverleaf interchange is a two-level interchange
Interchange (road)
In the field of road transport, an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream. It differs from a standard intersection, at which...
in which left turns, reverse direction in left-driving regions, are handled by ramp roads (US: ramps
Interchange (road)
In the field of road transport, an interchange is a road junction that typically uses grade separation, and one or more ramps, to permit traffic on at least one highway to pass through the junction without directly crossing any other traffic stream. It differs from a standard intersection, at which...
, UK: slip roads). To go left (in right-hand traffic), vehicles first continue as one road passes over or under the other, then exit right onto a one-way three-fourths loop ramp (270°) and merge onto the intersecting road.
Overview
Cloverleaf interchanges, viewed from overhead or on maps, resemble the leavesLeaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
of a four-leaf clover
Four-leaf clover
The four-leaf clover is an uncommon variation of the common, three-leaved clover. According to tradition, such leaves bring good luck to their finders, especially if found accidentally...
.
In the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
, cloverleaf interchanges existed long before the interstate system. They were originally created for busier interchanges that the original diamond interchange
Diamond interchange
A diamond interchange is a common type of road junction, used where a freeway crosses a minor road. The freeway itself is grade-separated from the minor road, one crossing the other over a bridge...
system could not handle. Their chief advantage was that they were free-flowing and did not require the use of such devices as traffic signals. This not only made them a viable option for interchanges between freeways (where such devices are typically not an option), but they could also be used for very busy arterials where signals could present congestion problems.
They are very popular in the U.S. and have been used for over 40 years as the Interstate Highway System
Interstate Highway System
The Dwight D. Eisenhower National System of Interstate and Defense Highways, , is a network of limited-access roads including freeways, highways, and expressways forming part of the National Highway System of the United States of America...
expanded rapidly. One problem is that, frequently, large truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
s exceeding the area speed limit
Speed limit
Road speed limits are used in most countries to regulate the speed of road vehicles. Speed limits may define maximum , minimum or no speed limit and are normally indicated using a traffic sign...
(i.e. 25 mph; 40 km/h) roll over. Another problem is the merging of traffic (see below). For these reasons, cloverleaf interchanges have become a common point of traffic congestion at busy junctions.
At-grade
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...
cloverleaf configurations with full four leafs and full outside slip ramps are extremely rare, though one exists in Toms River, New Jersey
Toms River, New Jersey
Toms River is a census-designated place and unincorporated area located within Toms River Township and is the county seat of Ocean County, New Jersey. It is part of a larger Toms River Township...
. Any other intersections with merely one, two, or three leaf ramps with outer ramps would not be designated a "cloverleaf" and simply be referred to as a Jughandle
Jughandle
A 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...
intersection.
History
The first cloverleaf interchange patented in the US by Arthur Hale, a civil engineerCivil engineer
A civil engineer is a person who practices civil engineering; the application of planning, designing, constructing, maintaining, and operating infrastructures while protecting the public and environmental health, as well as improving existing infrastructures that have been neglected.Originally, a...
in Maryland
Maryland
Maryland is a U.S. state located in the Mid Atlantic region of the United States, bordering Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware to its east...
, on February 29, 1916. Several cloverleafs were built in the late 1920s; however, it is unclear which was first.
A modified cloverleaf, with the adjacent ramps joined into a single two-way road, was planned in 1927 for the interchange between Lake Shore Drive
Lake Shore Drive
Lake Shore Drive is a mostly freeway-standard expressway running parallel with and alongside the shoreline of Lake Michigan through Chicago, Illinois, USA. Except for the portion north of Foster Avenue , Lake Shore Drive is designated as part of U.S...
(US 41) and Irving Park Road (ILL 19
Illinois Route 19
Illinois Route 19 is a major east–west arterial road in northeastern Illinois, United States. It runs from Illinois Route 25 in Elgin, to Lake Shore Drive on the north side of Chicago. Illinois 19 is long...
) in Chicago, Illinois, but a diamond interchange
Diamond interchange
A diamond interchange is a common type of road junction, used where a freeway crosses a minor road. The freeway itself is grade-separated from the minor road, one crossing the other over a bridge...
was built instead.
The first cloverleaf interchange built in the US was the Woodbridge Cloverleaf at Route 25
Route 25 (New Jersey)
Route 25 was a major state highway in New Jersey, United States prior to the 1953 renumbering, running from the Benjamin Franklin Bridge in Camden to the Holland Tunnel in Jersey City. The number was retired in the renumbering, as the whole road was followed by various U.S. Routes - U.S...
and Route 4
Route 4 (New Jersey)
Route 4 is a state highway in Bergen County and Passaic County, New Jersey, United States, that is also known as the Mackay Highway. The highway stretches from Route 20 in Paterson east to an interchange with Interstate 95, U.S. Route 1/9, U.S. Route 46, and U.S. Route 9W at the George Washington...
(now US 1/9 and Route 35
Route 35 (New Jersey)
Route 35 is a state highway in the U.S. state of New Jersey, primarily traveling through the easternmost parts of Middlesex, Monmouth, and Ocean counties. It runs from the entrance to Island Beach State Park in Berkeley Township, Ocean County to an intersection with Route 27 in Rahway, Union County...
) in Woodbridge Township, New Jersey
Woodbridge Township, New Jersey
-Communities:Many distinct communities exist within Woodbridge Township. Several of these communities have their own ZIP codes, and many are listed by the United States Census Bureau as census-designated places, but they are all unincorporated areas and neighborhoods within the Township that,...
. It opened in 1929, and has been replaced with a partial cloverleaf interchange. The original cloverleaf interchange was designed by the Rudolph and Delano building firm from Philadelphia, and was modeled after a plan from Buenos Aires
Buenos Aires
Buenos Aires is the capital and largest city of Argentina, and the second-largest metropolitan area in South America, after São Paulo. It is located on the western shore of the estuary of the Río de la Plata, on the southeastern coast of the South American continent...
, Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
The first cloverleaf west of the Mississippi River
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
opened on August 20, 1931 at Watson Road and Lindbergh Boulevard
Lindbergh Boulevard
Lindbergh Boulevard named after the aviator, Charles Lindbergh, is a section of U.S. Route 61 and U.S. Route 67 that extends through Missouri. Lindbergh Boulevard is home to Missouri's only traffic tunnel underneath a runway at Lambert International Airport....
near St. Louis, Missouri
St. Louis, Missouri
St. Louis is an independent city on the eastern border of Missouri, United States. With a population of 319,294, it was the 58th-largest U.S. city at the 2010 U.S. Census. The Greater St...
as part of an upgrade of US 66
U.S. Route 66
U.S. Route 66 was a highway within the U.S. Highway System. One of the original U.S. highways, Route 66 was established on November 11, 1926 -- with road signs erected the following year...
. This interchange, however, has since been replaced with a diamond interchange
Diamond interchange
A diamond interchange is a common type of road junction, used where a freeway crosses a minor road. The freeway itself is grade-separated from the minor road, one crossing the other over a bridge...
.
The cloverleaf was patented in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
on October 15, 1928. The first cloverleaf in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
opened in October 1935 at Slussen
Slussen
Slussen is an area of central Stockholm, connecting Södermalm and Gamla stan. The area is named after the locks between Lake Mälaren and the Baltic Sea. The locks themselves allow passage between these two bodies of water...
in central Stockholm
Stockholm
Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
, followed in 1936 by Schkeuditzer Kreuz near Leipzig
Leipzig
Leipzig Leipzig has always been a trade city, situated during the time of the Holy Roman Empire at the intersection of the Via Regia and Via Imperii, two important trade routes. At one time, Leipzig was one of the major European centres of learning and culture in fields such as music and publishing...
, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. This is now the interchange between the A 9 and A 14
Bundesautobahn 14
is an autobahn in eastern Germany.Currently, the route comprises two disconnected sections:* The old A 241. A North-South route in Mecklenburg-Vorpommern which runs from Wismar to Schwerin....
, and has a single flyover
Overpass
An overpass is a bridge, road, railway or similar structure that crosses over another road or railway...
from the westbound A 14 to the southbound A 9. Kamener Kreuz
Kamener Kreuz
The Kamener Kreuz was formerly a full cloverleaf interchange near Dortmund in North Rhine-Westphalia Germany where the Autobahnen A1 and A2 meet. It lies between the towns of Kamen and Bergkamen in the west and the city of Hamm and the municipality Bönen in the east...
was the first in continental Europe to open fully in 1937, at A 1 and A 2 near Dortmund
Dortmund
Dortmund is a city in Germany. It is located in the Bundesland of North Rhine-Westphalia, in the Ruhr area. Its population of 585,045 makes it the 7th largest city in Germany and the 34th largest in the European Union....
Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
.
Problems
A point of conflict is the merging of exiting and entering traffic in the same lane, known as weaving. Most road authorities have since been implementing new interchange designs with less-curved exit ramps that do not result in weaving. These interchanges include the diamondDiamond interchange
A diamond interchange is a common type of road junction, used where a freeway crosses a minor road. The freeway itself is grade-separated from the minor road, one crossing the other over a bridge...
, parclo
Parclo interchange
A partial cloverleaf interchange or parclo is a modification of a cloverleaf interchange. The parclo interchange was developed by the Ontario Ministry of Transportation as a replacement for the cloverleaf on 400-Series Highways, removing the dangerous weaving patterns and allowing for more...
and Single-point urban
Single-point urban interchange
A single-point urban interchange , also called a single-point interchange or single-point diamond interchange , is a type of highway interchange...
(SPUI) interchanges when connecting to an arterial road
Arterial road
An arterial road, or arterial thoroughfare, is a high-capacity urban road. The primary function of an arterial road is to deliver traffic from collector roads to freeways, and between urban centres at the highest level of service possible. As such, many arteries are limited-access roads, or feature...
, and the stack
Stack interchange
A stack interchange is a free-flowing grade separated junction between two roads.In countries where one drives on the right, left turns are handled by semi-directional flyover/under ramps...
or cloverstack when connecting to another freeway or to a busy arterial where signals are still not desired.
Not only are these ideas true for new interchanges, but they also hold when existing cloverleaf interchanges are upgraded. In Norfolk, Virginia
Norfolk, Virginia
Norfolk is an independent city in the Commonwealth of Virginia in the United States. With a population of 242,803 as of the 2010 Census, it is Virginia's second-largest city behind neighboring Virginia Beach....
, the interchange between U.S. 13
U.S. Route 13
U.S. Route 13 is a north–south U.S. highway established in 1926 that runs for from Interstate 95 just north of Fayetteville, North Carolina to the northeastern suburbs of Philadelphia, Pennsylvania, in Morrisville. In all, it traverses five states in the Atlantic coastal plain region,...
and U.S. 58
U.S. Route 58
U.S. Route 58 is an east–west U.S. Highway that runs for from U.S. Route 25E just northwest of Harrogate, Tennessee to U.S. Route 60 in Virginia Beach, Virginia. Until 1996, when the Cumberland Gap Tunnel opened, US 58 ran only inside the commonwealth of Virginia...
was originally a cloverleaf—it has since been converted to a SPUI
Spui
Spui is a Dutch term meaning a specific type of small sluice used for refreshing the network of waterways in a village or town. It may refer to the following things:*Spui, a river in the Netherlands...
. Also, many cloverleaf interchanges on California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
freeways, such as U.S. 101, are being converted to parclos
Parclo interchange
A partial cloverleaf interchange or parclo is a modification of a cloverleaf interchange. The parclo interchange was developed by the Ontario Ministry of Transportation as a replacement for the cloverleaf on 400-Series Highways, removing the dangerous weaving patterns and allowing for more...
. In Hampton, Virginia
Hampton, Virginia
Hampton is an independent city that is not part of any county in Southeast Virginia. Its population is 137,436. As one of the seven major cities that compose the Hampton Roads metropolitan area, it is on the southeastern end of the Virginia Peninsula. Located on the Hampton Roads Beltway, it hosts...
, a cloverleaf interchange between Interstate 64
Interstate 64
Interstate 64 is an Interstate Highway in the Midwestern and Southeastern United States. Its western terminus is at I-70, U.S. 40, and U.S. 61 in Wentzville, Missouri. Its eastern terminus is at an interchange with I-264 and I-664 at Bowers Hill in Chesapeake, Virginia. As I-64 is concurrent with...
and Mercury Boulevard
U.S. Route 258
U.S. Route 258 is a spur of US 58 in the U.S. states of North Carolina and Virginia. The U.S. Highway runs from US 17 Business and North Carolina Highway 24 Business in Jacksonville, North Carolina north to Virginia State Route 143 at Fort Monroe in Hampton, Virginia...
has been partially unwound into a partial stack interchange
Stack interchange
A stack interchange is a free-flowing grade separated junction between two roads.In countries where one drives on the right, left turns are handled by semi-directional flyover/under ramps...
. During 2008 and 2009, four cloverleaf interchanges along I-64/U.S. 40
U.S. Route 40
U.S. Route 40 is an east–west United States highway. As with most routes whose numbers end in a zero, U.S. 40 once traversed the entire United States. It is one of the original 1920s U.S. Highways, and its first termini were San Francisco, California, and Atlantic City, New Jersey...
in St. Louis, Missouri
Missouri
Missouri is a US state located in the Midwestern United States, bordered by Iowa, Illinois, Kentucky, Tennessee, Arkansas, Oklahoma, Kansas and Nebraska. With a 2010 population of 5,988,927, Missouri is the 18th most populous state in the nation and the fifth most populous in the Midwest. It...
were replaced with SPUI
Spui
Spui is a Dutch term meaning a specific type of small sluice used for refreshing the network of waterways in a village or town. It may refer to the following things:*Spui, a river in the Netherlands...
s as part of a major highway-renovation project to upgrade the highway to Interstate standards.
A compromise is to add a collector/distributor road next to the freeway; this doesn't eliminate weaving but moves it off the main lanes of the freeway. An example of this is the State Highway 23/Interstate 43
Interstate 43
Interstate 43 is a intrastate Interstate Highway located entirely within the U.S. state of Wisconsin, connecting Interstate 39 and Interstate 90 in Beloit with Milwaukee and U.S. Route 41 and U.S. Route 141 in Green Bay. I-43 is the 5th longest intrastate Interstate Highway of the Interstate...
interchange in Sheboygan, Wisconsin
Sheboygan, Wisconsin
-Airport:Sheboygan is served by the Sheboygan County Memorial Airport, which is located several miles from the city.-Roads:Interstate 43 is the primary north-south transportation route into Sheboygan, and forms the west boundary of the city. U.S...
, where the exit/entrance roads on and off Highway 23 are two lanes next to the main I-43 freeway on the north and southbound sides of the road.
A few cloverleaf interchanges in California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
have been rebuilt to eliminate weaving on the freeway while keeping all eight loop ramps, by adding bridges.
Several cloverleafs have been eliminated by adding traffic light
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...
s on the non-freeway route. Sometimes, this is even done at the intersection of two freeways, particularly when one freeway terminates at an interchange with another. An example of this is in Lakewood, Washington
Lakewood, Washington
Lakewood is a city in Pierce County, Washington, United States. The population was 58,163 at the 2010 census.-History:Lakewood was officially incorporated on February 28, 1996. Historical names include Lakewood Center and Lakes District...
, at the interchange between Interstate-5 and Wash.-512. A visible ramp stub shows that one of the four leaves was removed; thus eliminating an unsafe weave on I-5. In the future, the traffic signal will be replaced by a two-lane flyover, completing the freeway-to-freeway interchange once again. http://maps.google.com/maps?f=q&hl=en&q=seattle+wa&btnG=Search&t=k&ll=47.16297,-122.479792&spn=0.002932,0.009205&t=k
Cloverleafs also tend to occupy much more land than any other kind of interchange (with the possible exception of stack interchange
Stack interchange
A stack interchange is a free-flowing grade separated junction between two roads.In countries where one drives on the right, left turns are handled by semi-directional flyover/under ramps...
s).
Numerous cloverleaf intersections in the Lower Mainland
Lower Mainland
The Lower Mainland is a name commonly applied to the region surrounding and including Vancouver, British Columbia, Canada. As of 2007, 2,524,113 people live in the region; sixteen of the province's thirty most populous municipalities are located there.While the term Lower Mainland has been...
of British Columbia, Canada require the merging of traffic from the clover directly onto the collector/distributor lane. This requires the slowly-moving driver coming around the roundabout to merge with the quickly-moving driver exiting on the collector/distributor lane with no opportunity to accelerate to match the flow of the oncoming driver. This speed discrepancy in merging can be as great as 65 km/h (approx. 43 mph).
The cloverleaf interchange was not implemented in great numbers in the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
, because of these performance problems. There were originally three, one in Redditch
Redditch
Redditch is a town and local government district in north-east Worcestershire, England, approximately south of Birmingham. The district had a population of 79,216 in 2005. In the 19th century it became the international centre for the needle and fishing tackle industry...
and two in Livingston
Livingston, Scotland
Livingston is a town in West Lothian, Scotland. It is the fourth post-WWII new town to be built in Scotland, designated in 1962. It is about 15 miles west of Edinburgh and 30 miles east of Glasgow, and is bordered by the towns of Broxburn to the northeast and Bathgate to the northwest.Livingston...
. One of the Livingston examples was remodeled in the mid 2000s as part of a public transport project. The major junction of the M11
M11 motorway
The M11 motorway in England is a major road running approximately north from the North Circular Road in South Woodford in north-east London to the A14, north-west of Cambridge.-Route:...
and A14 at the Girton interchange near the outskirts of Cambridge
Cambridge
The city of Cambridge is a university town and the administrative centre of the county of Cambridgeshire, England. It lies in East Anglia about north of London. Cambridge is at the heart of the high-technology centre known as Silicon Fen – a play on Silicon Valley and the fens surrounding the...
consists of two cloverleaf loops, making essentially a 'half' cloverleaf interchange. This junction is prone to heavy traffic congestion at peak times, chiefly due to the requirement for westbound A14 traffic to exit the main dual carriageway
Dual carriageway
A dual carriageway is a class of highway with two carriageways for traffic travelling in opposite directions separated by a central reservation...
, traverse one of the cloverleaf loops at slow speeds, and then engage in weaving with traffic exiting the M11, in order to continue westward along the A14. In Ireland, a partial cloverleaf set-up exists at the interchange of the N4 and the M50 in Dublin, allowing free-flow movements in all directions. A similar design has been implemented at the N7/M50 interchange.