East of I-35, I-80 meets up with US 65 on the outskirts of Altoona. The two routes only share the highway for as US 65 splits away at the next exit. Here, US 6 rejoins I-80 for the second time and the Interstate returns to its four-lane configuration. After a third exit for Altoona, the Interstate resumes its rural limit. Near Colfax, the highways cross the South Skunk River. After an interchange with Iowa 117, the highway is forced to the north to avoid crossing the river multiple times. As it returns south to its original line, it meets CR F48, which was another former alignment of US 6. At the Iowa 14 exit in Newton, US 6 exits off the Interstate. East of Newton is an interchange that serves the Iowa Speedway.