 By the late 1980s, traffic levels were so high that the route was upgraded into a six-lane grade-separated limited-access expressway, with most of the intersections converted into right-in/right-out interchanges, and a few others being converted into more standard interchanges.The upgrade of the route was completed by the early 1990s.The US 50/US 301 concurrency on the Eastern Shore included a four-lane drawspan connecting Kent Island to the mainland; the upgrade from 4 lanes to 6 lanes included rerouting US 50/US 301 onto a high-level fixed span just north of there, with the drawspan now being used for MD 18.