The southern end of Iowa 150 changed again in 1984. After I-380, which was constructed parallel to Iowa 150 between Cedar Rapids and Center Point, was opened to traffic, Iowa 150's routing south of Iowa 101 was essentially redundant to the new interstate. As a result, Iowa 150 was rerouted over Iowa 101 south to Vinton. The vacated section of Iowa 150 was renumbered Iowa 920 from old Iowa 101's north end to Center Point and Iowa 921 from Center Point to Cedar Rapids.