The Missouri Dept. of Transportation is building its second “diverging diamond” interchange design that requires motorists at an interchange to temporarily drive on the left side of the road. It was devised by an engineer in graduate school who wasn’t aware the concept already existed in Europe. The Federal Highway Administration has tested and presented the design, and a dozen states are considering using it
The design calls for the approach road on either side of the interchange to curve to the left, so the driver can easily enter the highway on a limited-access ramp without fear of oncoming traffic from the other side of the road. Through-traffic continues on the left side of the road until reaching a second stoplight, where it shifts back to the more familiar right side.