Just overnight to Rest/Sleep I think is okay, these places are made for drivers to rest & get sleep while on long trips. I slept in my Chevrolet truck overnight & didn't have any issues. Most of the rest stops have a sign "No Camping" which to me means staying for a few days and or setting up a tent.
If the trucks do I don't see why you shouldn't be able to
I'm sure if you are tired they aren't going to say no!
You'd have to check with the Iowa DOT
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