The original cloverleaf interchange was patented in the United states by Arthur Hale in 1916. Hale’s design, though used throughout the world, has a few flaws, the most serious of which are the safety issues that arise from cars merging on and off the highway in the same lane (known as weaving). The Ontario Ministry of Transportation designed a modification to the original cloverleaf to address its shortcomings for the 400-series highways. The redesign creates more room for acceleration and deceleration and avoids the notoriously dangerous weaving lane. The Parclo has been embraced throughout the world as one of the most popular freeway-to-arterial interchange designs. As if this didn’t make it on one of those “A Part of Our Heritage” ads! Check wikipedia for the locations of Parclo interchanges along the 400-series highways so you too can experience this great Canadian design.