Editing Partial cloverleaf interchange (section)

===A4===
[[File:Parclo A4.svg|thumb|upright|A4 Interchange for right-hand traffic, or B4 interchange for left-hand traffic]]
The parclo A4 (also called "six-ramp partial cloverleaf") contains six ramps.<ref>[http://www.kurumi.com/roads/interchanges/sixramp.html Six-ramp partial cloverleaf interchanges]</ref> On each side on the freeway, there is an (often multi-lane) exit ramp, followed by a loop ramp and directional ramp entering the freeway. The on-ramps are in the same configuration as a cloverleaf interchange, but there is one off-ramp for each freeway direction instead of two, typically requiring a controlled intersection where the off-ramp meets the arterial road.

The ''parclo A4'' is one of the most popular designs, as all movements from the arterial road to the entrance ramps are made by right-hand turns, providing for a safer entrance to the freeway by eliminating left-hand turns into opposing traffic (which require queues waiting to make such turns). This also makes logical sense since freeways have a higher capacity than arterials and right-turn ramps serve effectively to absorb capacity and reduce traffic on the arterial.

Some parclos have the right-turning (directional) on-ramp leave the arterial road after the exit ramp intersection. This configuration is often used when another road meets the freeway off-ramp and gives traffic from this road the option of turning right to use the directional on-ramp to enter the freeway.

Traffic exiting the freeway to the arterial road is provided with a long, relatively straight exit ramp, preventing most speed-related rollovers. These exit ramps are also frequently multi-laned to accommodate traffic turning left, right, or going straight ahead in some cases. Traffic signals are commonly installed at the end of the exit ramp to regulate the freeway traffic flowing onto the arterial.

The parclo A4 is particularly well-suited to suburban areas with high traffic levels. Ontario freeways throughout much of the southern portion of the province, especially freeways in the [[Golden Horseshoe]] and [[Ottawa]] area, use the A4 parclo.  These interchanges also exist on some highways in the [[Montreal]] area.   One issue in suburban areas is the presence of three conflict points in each direction for pedestrians and non-motorised vehicles, the first of which is a moderate speed, low visibility conflict.

Caltrans favors this form for some recent projects, for example the reconstruction of [[Interstate 880 (California)|I-880]] and other highways in the [[San Francisco Bay Area]] and the [[Greater Los Angeles Area]]. They often replaced previous full cloverleafs. All exiting traffic for both directions has a relatively straight ramp and is controlled by a traffic light. Running off the road on an entering ramp is much less likely than on an exiting ramp. [[Ramp meter|Metering lights]] are a common feature on the entering ramps.

[[File:ParcloSK.jpg|thumb|An A4 parclo at [[Saskatchewan Highway 1]] (the [[Trans Canada Highway]]), [[Saskatchewan Highway 39]]  and [[Saskatchewan Highway 301]]. The eastbound directional onramp is located further south of the overpass and is not pictured.]]
The junction of Saskatchewan Highway 1 (east-west), Saskatchewan Highway 39 (south, part of the CanAm route)  and Saskatchewan Highway 301 (north) is an A4 parclo.  Highway 1 serves as the freeway, while Highway 39/301 is the arterial road.