Around here farm registered road vehicles are still required to run road tax fuel, unless they never leave the property.
Lou I'm sure there are exceptions but overall how hrs out of a tractor's total hrs are spent on the road? Based on what I see around here it's pretty low.
Around here it varies quite a bit,
the smaller family sized farms that still chop (silage hay and corn) into wagons and not trucks such as the large operations do.
As an example for haylage,
going to mow is road to the field a few miles, several hours in the field and then back to the farm,
tedding, raking is the same,
then chopping, one tractor on the chopper to the field and then in the field chopping, then
2 or 3 tractors and people hauling and unloading, these tractors will spend the majority of the day roading
back and forth, more road time then in the field and unloading.
Then the silo blower or bagger tractor is sitting and working all day with no road time.
In this area the roads are commonly used to get to and from fields and even from one field to the next.
All in all it's hard to say how many hours are field and how many are road, but quite a few road hours in the course of a growing and harvest season.