In a reversal from years of work, the Iowa DOT appears to have scrapped or at least put on hold plans to build an interchange at the intersection of US 30 and US 218 (the Youngville Station corner).
Instead, based on this statement for a meeting this Wednesday, the current plan is to create a J-turn intersection. There are no intersections of this type in the state, although at one point they were proposed for the 65/330/117 intersection and US 151/X20 at Springville.
The J-turn is like a Michigan Left but isn’t, because the latter allows traffic on the lesser road to go straight through. The intersection is illustrated in the PDF linked above.
On the positive side, not having an interchange would reduce construction costs and have less impact on the Youngville Station area, since the building is right by the road. On the negative side, I’m ambivalent about this whole “J-turn” thing and implementation of yet another unfamiliar transportation concept in Iowa. (Iowa hasn’t gone roundabout-mad like Wisconsin. Yet.)
CORRECTION: An interchange is still on the table. This’ll teach me to wait until the maps are released.