The most recent environmental assessment (large PDF) for an expanded I-380 on the north side of Linn County has something new for the state of Iowa: consecutive diverging diamond interchanges.
Today, there is only one diverging diamond interchange in the state: the one at the far fringe of Waukee/West Des Moines. Two others are planned in the Des Moines area, I-35 at 1st Street in Ankeny and I-35/80 at Hickman Road.
The plan for Linn County replaces I-380’s diamond interchange at Boyson Road with a DDI and also puts a DDI at the new Tower Terrace Road interchange to the north. I-380 will be six-laned all the way up to the County Home Road exit (that currently ends at Blairs Ferry Road).
There will be a hearing on Jan. 22, with a formal presentation, which we don’t get much nowadays.