I-875 (proposed)  Ohio; Kentucky; Indiana (link)

A proposed $1.6 billion, 225-mile outer beltway around Cincinnati, concentric with I-275. The proposed route: "would pass through Brown County, Ohio, crossing into Kentucky via the new Maysville-Aberdeen bridge, along Kentucky 9 near Brooksville, then intersecting the cities of Falmouth in Pendleton County, Williamstown in Grant County, Owenton in Owen County, through Carroll County and into Gallatin County. The road would connect with the Markland Dam near Warsaw before crossing into Indiana."

There has not been much buzz about this route since 1997, however.