“While beneficial to operations and safety, truck-only lanes are cost prohibitive with the current financial constraints of the Iowa DOT,” the agency said in a technical memo last July.

It added that expanding to six lanes would bring many of the same benefits. The report did not recommend lane restrictions or speed restrictions, but it said they could be pursued in the future.

As for expanding U.S. 30 and U.S. 34, the DOT found that would not bring sufficient benefits. The study also examined the kind of changes that might come from the trend toward automated driving.

The DOT still has work to do. It still hasn’t detailed its findings on financing improvements with tolls. That would be a controversial step, and one that would require legislation.

“We considered it our responsibility to at least look at it,” Hofer said.

Taking such a step would mean some operational and safety benefits, in that improvements could be done more quickly. But it also would be a change to how the state traditionally funds road improvements. That report is due soon.