I just drove the short freeway near Standish and noticed that it has stubs at the M-13 end. (I know that M-13 is old US 23 from here for some distance south.) Where was this freeway supposed to go, and would it have been US 23 or an x75?
It was roughly going to follow the coast up to Alpena. It probably would've split the difference between M-65 and the coastal US-23. It likely would've been signed as US-23.
Far more info: http://www.michiganhighways.org/indepth/US-23_sunriseside.html
There was indeed traffic on 23, but I didn't see enough to warrant a freeway versus the current four-lane undivided road.
Note the time of year you drove it. Traffic is much heavier during the summer for obvious reasons.
I could potentially see the need, then