Have you ever seen a road junction that looks like it has a cloverleaf in the middle? Well, funnily enough they’re called cloverleaf interchanges. But sometimes, they don’t have all four loops and so they’re known as partial cloverleaf interchanges or parclos.
More specifically, a partial cloverleaf interchange is an alteration of the cloverleaf interchange designed by the Ontario Ministry of Transportation initially to widen one of its highways:
In the years that followed, Ontario continued to cement the reputation for high safety standards that it first established with the QEW. When it came time to widen the 401 in the late ’60s, the DHO modified the cloverleaf design, which had originally featured eight loop ramps, to reduce weaving on high-speed roads: the partial cloverleaf, featuring just two off-ramps, improved safety, and only minor work was required to modify existing interchanges. While dozens of eight-ramp cloverleaf interchanges were built on the QEW, 400, and 401 from 1937 up until the 1960s, only one remains, at Belleville. The partial cloverleaf, or “parclo,” is now common throughout North America.
via TVO
Outside of North America, parclos are also used in European countries including Hungary, the Netherlands, and the United Kingdom. It was
To add another colloquialism to this blog, we also have a parclo variation known as a “dumbell” (due to its appearance) which is a combination of a diamond interchange and the roundabout interchange. According to roads.org.uk, the UK’s first full motorway interchange was a variation on this—or “a parclo with roundabouts”, built on the Preston Bypass and opened in 1958.
Filed under: Canada infrastructure roads