Currently, the Iowa DOT is pouring tens of millions of dollars into upgrading urban interstate systems in Council Bluffs and Sioux City. I-80 in Iowa City has been upgraded to six lanes, and the complete rebuild of I-235 in Des Moines is a decade in the past now.
But as this article in the Des Moines Register points out, rural interstates are carrying enough traffic that they need to be six-laned, too. (And that’s without mentioning, again, that four-laning US 20 still isn’t finished.)
The biggest choke points, in my personal experience, are I-380 between Cedar Rapids and Iowa City and I-35 between Ankeny and Ames. Those aren’t the only locations the state is looking at, though: The entire eastern half of I-80 could be a candidate for six-laning in the future.
The closest comparative project would be I-80 in eastern Nebraska, recently opened to six lanes from Omaha to Lincoln. Ohio finished six-laning I-71 from Columbus to Cleveland just before this Thanksgiving.
The Iowa projects would be ambitious, and currently only done piecemeal, as with a proposed bridge replacement on I-35 south of Ames. The long-range plan, such as it is, will likely be a factor in the gas tax debate next legislative session.