Utah has one. I think they are more common when the non freeway road has very high levels of traffic. An even more efficient interchange is the roundabout int

Utah has one. I think they are more common when the non freeway road has very high levels of traffic. An even more efficient interchange is the roundabout interchange https://en.wikipedia.org/wiki/Roundabout_interchange https://en.wikipedia.org/wiki/Roundabout_interchange The only problems with the roundabout interchange are that you need two different bridges spaced a distance apart which can add construction costs and they require more area than a standard interchange, although about the same as a clover leaf.