Switching from one busy highway to another can be a logic-defying, heart-stopping endeavor—one that a carefully engineered interchange is meant to ease.
In the United States and in many other countries, drivers can make right turns easily without crossing any lanes of traffic. The common “cloverleaf” interchange takes advantage of this fact—in effect, replacing a 90-degree left turn with a 270-degree right turn. The opposite would be true in England and other countries where drivers stay to the left side of the road.