Cloverleaf interchange

Source: Wikipedia, the free encyclopedia.
A cloverleaf with collector/distributor roads.
A typical cloverleaf interchange with collector/distributor roads in Cutlerville, Michigan, located at: 42°50′56″N 85°40′43″W / 42.848912°N 85.678689°W / 42.848912; -85.678689
The Kathipara Cloverleaf interchange in Chennai, India
Many old cloverleaf interchanges elongate the ramps in the direction of the surface road. This one in Alhambra, California has been supplemented with collector/distributor roads, 34°04′18″N 118°07′23″W / 34.071659°N 118.122938°W / 34.071659; -118.122938
Slussen, Stockholm, 59°19′14″N 18°04′21″E / 59.32063°N 18.072501°E / 59.32063; 18.072501
In this cloverleaf in Long Beach, California, two bridges are used to eliminate weaving among cars entering and exiting the westbound lane, 33°48′21″N 118°08′31″W / 33.80595°N 118.142047°W / 33.80595; -118.142047

A cloverleaf interchange is a two-level

traffic weaving
.

Overview

A cloverleaf interchange near Sharjah International Airport in the United Arab Emirates, 25°17′55″N 55°35′37″E / 25.298611°N 55.593611°E / 25.298611; 55.593611

Cloverleaf interchanges, viewed from overhead or on maps, resemble the leaves of a four-leaf clover or less often a 3-leaf clover. In the

arterials
where signals could present congestion problems.

They are common in the United States and have been used for over 40 years as the Interstate Highway System expanded rapidly. One problem is that, frequently, large trucks exceeding the area speed limit roll over.[1] 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 cloverleaf configurations with full four leaves and full outside slip ramps are extremely rare, though one exists in Toms River, New Jersey.[2] Any other intersection 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
or parclo intersection.

History

Background

The first cloverleaf interchange

patented in the US was by Arthur Hale, a civil engineer in Maryland, on February 29, 1916.[3][4]

A modified cloverleaf, with the adjacent ramps joined into a single two-way road, was planned in 1927 for the interchange between

Chicago, Illinois, but a diamond interchange
was built instead.

Beginning

The first cloverleaf interchange built in the United States was the Woodbridge Cloverleaf[5] at intersection of the Lincoln Highway (Route 25) and Amboy—now St. Georges—Avenue (Route 4) (now U.S. 1/9 and Route 35) in Woodbridge Township, New Jersey.[6][7][8] It opened in 1929,[9] although it has since been replaced with a partial cloverleaf interchange.[10] Before the cloverleaf was replaced in the late-2000s, it was judged eligible for inclusion in the National Register of Historic Places. Because of this, a commemorative film [5] was made of the cloverleaf.[11] The original cloverleaf interchange design was adapted by the Rudolph and Delano building firm from Philadelphia, from a photo Delano saw on a magazine cover about a highway in Buenos Aires, Argentina. The original inventor is unknown.

The first cloverleaf west of the

St. Louis, Missouri, as part of an upgrade of U.S. 66.[12]

The first cloverleaf interchange in Canada opened in 1937 at the junction of the Queen Elizabeth Way (QEW) and Provincial Highway 10 in Port Credit, Ontario (now a part of Mississauga, Ontario). As originally built, Highway 10 passed over the QEW. In 1962, the interchange was rebuilt with sub-collector roads along the QEW, and the orientation was also changed so that Highway 10 then passed under the QEW. The interchange was further modified between 2008 and 2010 by removing all but one loop ramp, creating a partial cloverleaf/diamond hybrid.

The cloverleaf was patented in

Slussen in central Stockholm, Sweden, followed in 1936 by Schkeuditzer Kreuz near Leipzig, Germany. This is now the interchange between the A 9 and A 14, and has a single flyover from the westbound A 14 to the southbound A 9. Kamener Kreuz was the first in continental Europe to open fully in 1937, at A 1 and A 2 near Dortmund, Germany
.

Problems

The primary drawback of the classic design of the cloverleaf is that vehicles merge onto the highway at the end of a loop immediately before other vehicles leave to go around another loop, creating conflict known as

parclo and single-point urban interchanges (SPUI) when connecting to an arterial road in non free-flowing traffic on the crossroad and the stack or clover and stack hybrids
when connecting to another freeway or to a busy arterial in free-flowing traffic 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

SPUI
.

A compromise is to add a

collector/distributor road next to the freeway; this does not eliminate weaving but moves it off the main lanes of the freeway. An example of this is the State Highway 23/Interstate 43 interchange in Sheboygan, Wisconsin
, 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 have been rebuilt to eliminate weaving on the freeway while keeping all four loop ramps, by adding bridges, similar to braided ramps.

Several cloverleaf interchanges have been eliminated by adding

ramp stub shows that one of the four leaves was removed, thus eliminating weave on I-5.[13] In the future, the traffic signal will be replaced by a two-lane flyover, completing the freeway-to-freeway interchange once again.[citation needed
] Cloverleaf interchanges also tend to occupy much more land than any other kind of interchange.

Numerous cloverleaf intersections in the Lower Mainland 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 loop ramp 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 differential in merging can be as great as 65 km/h (approx. 43 mph).

The cloverleaf interchange was not implemented in great numbers in the

A14 westbound traffic weaving with M11 traffic.[14] This interchange was redesigned in 2019 to remove one of the loops. In Ireland, partial cloverleaf set-ups exist at the interchanges of the main roads out of Dublin and the M50, allowing free-flow movements in all directions. The Red Cow Interchange
is an example.

Most cloverleaf interchanges have been phased out in Ontario, but some close variants do remain with similar traffic flows. The main difference however is that adjacent on and off ramps are shared together by single bidirectional carriageways. Examples include the

Dixon Road
are also other examples; however, one quadrant of each has a loop missing.

See also

Comparison of traffic flows for some four-legged complete interchanges (animation)

References

  1. ISBN 0-309-06608-5
    .
  2. ^ Google Maps
  3. ^ Wie man Autobahnen kreuzungsfrei kreuzt (German) Archived March 5, 2005, at the Wayback Machine
  4. ^ Patent no. 1173505 at Google Patent Search
  5. ^ a b The Woodbridge Cloverleaf: Onramps to Innovation, retrieved 2022-07-20
  6. ^ "The Cloverleaf Interchange". WhereRoadsMeet. Archived from the original on 2008-05-14. Retrieved 2008-12-21.
  7. ^ MartÃn, Hugo (April 7, 2004). "A Major Lane Change". Los Angeles Times. Retrieved 2008-12-21.
  8. ISBN 978-0-618-81241-7
    .
  9. ^ "Woodbridge Cloverleaf Historical Marker". www.hmdb.org. Retrieved 2022-07-20.
  10. ^ "Routes 1&9-35 Interchange Improvements, Project Description, Construction Updates, Commuter Information". New Jersey Department of Transportation. Retrieved 2008-12-21.
  11. ^ "Woodbridge Cloverleaf". Hunter Research, Inc. Retrieved 2022-07-20.
  12. ^ A Bit of Missouri 66 History
  13. ^ 47°09′47″N 122°28′50″W / 47.1630484°N 122.4804883°W / 47.1630484; -122.4804883
  14. Highways Agency. Section 5-3. Archived
    (PDF) from the original on 2021-12-16. Retrieved 2021-12-16.

External links

Wikimedia Commons has media related to Cloverleaf interchanges.
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