Editing Cloverleaf interchange (section)

== 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 [[Grade separation#Weaving|weaving]]. Weaving limits the number of lanes of turning traffic. 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 [[diamond interchange|diamond]], [[parclo interchange|parclo]] and [[single-point urban interchange]]s (SPUI) when connecting to an [[arterial road]] in non [[Free-flow interchange|free-flowing traffic]] on the crossroad and the [[stack interchange|stack]] or [[Interchange (road)#Combination interchange|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 [[Norfolk, Virginia]], the interchange between [[U.S. Route 13|US&nbsp;13]] and [[U.S. Route 58|US&nbsp;58]] was originally a cloverleaf—it has since been converted to a [[SPUI]]. Also, many cloverleaf interchanges on [[California]] freeways, such as U.S. 101, are being converted to [[parclo interchange|parclos]]. In [[Hampton, Virginia]], a cloverleaf interchange between [[Interstate 64]] and [[U.S. Route 258|Mercury Boulevard]] has been partially unwound into a partial stack interchange. During 2008 and 2009, four cloverleaf interchanges along [[I-64 (MO)|I-64]]/[[U.S. Route 40 in Missouri|US&nbsp;40]] in [[St. Louis]], [[Missouri]], were replaced with [[Single-point urban interchange|SPUIs]] as part of a major highway-renovation project to upgrade the highway to Interstate standards. The original cloverleaf interchange in [[Delmont, Pennsylvania]] between Routes 22 and 66 was also converted to a [[SPUI]].

A compromise is to add a [[Local-express lanes|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 [[Wisconsin Highway 23|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 [[traffic light]]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]], at the interchange between [[Interstate 5 (Washington)|Interstate 5]] and [[Washington State Route 512]], where a visible [[ramp stub]] shows that one of the four leaves was removed, thus eliminating weave on I-5.<ref>{{coord|47.1630484|N|122.4804883|W}}</ref> In the future, the traffic signal will be replaced by a two-lane flyover, completing the freeway-to-freeway interchange once again.{{citation needed|date=July 2021}} 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&nbsp;km/h (approx. 43&nbsp;mph).

The cloverleaf interchange was not implemented in great numbers in the [[United Kingdom]], because of these performance problems. There were originally three, one in [[Redditch]] and two in [[Livingston, Scotland|Livingston]]. One of the Livingston examples was remodeled in the mid-2000s as part of a public transport project. The Girton interchange near Cambridge was a "half"-cloverleaf interchange that regularly experienced peak-time congestion due to [[A14 road (Great Britain)|A14]] westbound traffic weaving with [[M11 motorway|M11]] traffic.<ref>{{Cite web|last=Atkins|author-link=Atkins_(company)|title=The A14 Girton to Felixstowe Congestion Study Report| url=https://www.eastsuffolk.gov.uk/assets/Planning/Suffolk-Coastal-Local-Plan/Document-Library/Infrastructure/A14-congestion-study-2005-Final-Report-2.pdf|url-status=live|access-date=2021-12-16| website=East Suffolk Council|publisher=[[Highways England|Highways Agency]]| at=Section 5-3|archive-url=https://web.archive.org/web/20211216171544/https://www.eastsuffolk.gov.uk/assets/Planning/Suffolk-Coastal-Local-Plan/Document-Library/Infrastructure/A14-congestion-study-2005-Final-Report-2.pdf |archive-date=2021-12-16 }}</ref> This interchange was [[A14 road (England)#A14 Cambridge to Huntingdon Improvement Scheme|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|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 [[Ontario Highway 62|Highway 62]] and [[Ontario Highway 401|Highway 401]] interchange in [[Belleville, Ontario]], the [[Ontario Highway 4|Highway 4]] and [[Ontario Highway 401|Highway 401]] in [[London, Ontario]], as well as the [[Lawrence Avenue]] and [[Don Valley Parkway]] interchange in Toronto. The [[Don Mills Road]] and [[Don Valley Parkway]] and the [[Ontario Highway 27|Highway 27]] and [[Dixon Road]] are also other examples; however, one quadrant of each has a loop missing.