Six-laning Interstate 80 across Iowa would necessitate replacement of every bridge along the way outside of the urban areas. As part of the Iowa DOT’s comprehensive statewide study of the interstate, it has studied which locations would have the least hardship if an existing bridge weren’t replaced and the road closed. One example that’s already in planning is 108th Street in Jasper County as part of building new bridges across the Skunk River.
Not surprisingly, Pottawattamie, Cass, and Adair counties have most of the bridges at lowest priority in the evaluation (PDF).