Around here it's wheat - The Palouse. One must always be on guard when traveling the county roads in this area. USUALLY there will be a vehicle in the lead with lights flashing and some type of "wide vehicle" sign.
The tractor/cultivator or combine can take the entire road. I've always been able to find a pull-off or driveway to wait for their passing.
The tractor or combine will have its light flashing and traveling at VERY reduced speeds.
I've never, in my 38 years here, seen nor heard of this situation requiring any intervention from LEO.
Whether the tractor or combine is under their own power or on a trailer - the "unit" will still be just as wide.
However - I do wonder about the city folks, their uber fast BMW's and this exact situation. I guess it all works itself out - never seen an accident.
Either that or somewhere there are quite a few fast cars all balled up and in a big pile.
The young, slick city dude, his fast sports car, a vivacious blond - - see them on the county back roads very often. God must be very forgiving......