ca. 1960: The Northeast Mixmaster was an integral part of Iowa’s interstate system from the beginning. Photo via Iowa DNR’s Historic Aerial Photo Project because the Iowa Orthographic website wasn’t working (noooo!).
The most complex interchange in Iowa is going to be turned into the most advanced interchange in Iowa.
The Northeast Mixmaster opened to east-west traffic in 1960 and north-south traffic in 1965 and 1967. In the 2000s, new north-south through lanes were built, and the north-south loops modified, but the east-west left exits remained in place.
Sixty years later, that’s all going to change. A meeting tomorrow night in Des Moines is the public’s first glimpse of a future long-term reconstruction of the Northeast Mixmaster that will eliminate the last left exits in Iowa (since I-29/480 is also going to change).
The biggest component programmed in so far, aside from rebuilding nearby surface-street bridges to accommodate changes, is a new two-lane ramp from eastbound 80 to northbound 35 plus. Currently, this is a one-lane left exit signed at 45 mph. That won’t be done until mid-2023. Along with that would be the two “farthest-out” exit ramps: WB 80 to NB 35 and EB 80 to SB 235. Here’s a map with only the earliest part shown (PDF).
Then, in 2024 and later, more new bridges and big flyover ramps would be built (PDF). The middle of the mixmaster would have three levels. Every exit with two exceptions would be two lanes. Those exceptions are the lightest traveled: EB 80 to SB 235 and NB 235 to WB 80, the latter being the only interior ramp left in the whole thing.
All of the exits would start farther back than where they are now, and all would have a single point of exit from the mainline. That is, all traffic to both directions would exit at the same time and split later.
We’ll still have what’s around now for a while, but big things are in the future.