Invented in Mexico by civil engineer Francisco Mier, the continuous flow intersection or CFI was developed as a lower cost transportation solution for congested intersections. The design both costs less than conventional interchanges or SPUI’s and requires less right of way. The CFI reduces construction time and requires minimal closures to existing facilities to build.
The CFI separates traffic turning left from a highway mainline at a crossover signal a few hundred feet ahead of the main intersection. While oncoming traffic is stopped, motorists turning left cross the oncoming lanes and enter a far left turn lane at the main intersection. Since drivers have already crossed the lanes of oncoming traffic, they will turn left onto the cross street at the same time that through traffic is also moving. This configuration eliminates the extra step in the light cycle required to move left turns through separately and allows extra “green light time” to be redistributed throughout the intersection.
Initial CFI’s were implemented by 2005 in Baton Rouge, Louisiana, Maryland and New York with positive results.
Source: UDOT Continuous Flow Intersection Tutorial.