"clear the mud from a very small area by the field entrance, if necessary lay some hardcore down. Then place a trough near the entrance - how you fill it with water is up to you - hose, rainwater, water in containers transported over, whatever. Next drive the tractor to the mud free area, dip a stiff broom in the water"
The longest trailers towable behind tractors are about 44ft plus drawbar(an artic lorry trailer), stick a tractor on the front and you're looking at about 20metres in length. Once you've handbrushed the 4-16 wheels of tractor plus implement/trailer of 0-12 wheels (which will take how long?) the mud is going to build up after a few repeats of that. So hardcore is out of the question. It pretty much has to be concrete or tarmac (which will need to cleaned each time too)?
Now to let other tractors into the field while you laboriously spend your day cleaning, you could well be needing space for another 20m tractor/trailer length to get in the field, put that 3x20m pad upto 3x40m, there'll probably be some king of queue building up so at least a 3x60m concrete pad in each and every field.
With grass, okay so you wouldn't have an artic trailer, but around 12-15m tractor/trailer (8 wheels) with a round trip of around 10mins (maybe 3 tractors/trailers on). You'd be needing maybe 3 times as many tractors/trailers/men to keep up with the 'harvester' in order to clean them each trip
"you could always invest in tractor mounted brushes"
They'd block up, and would never be stiff enough to 'sweep' the mud off, especially clay like mud. Plus the vast majority builds up in between the tread anyway so wouldn't make much difference
Okay, so not typical (nor my picture), but how do you get this much mud off with a brush? And how long would it take?
"Dirtworker FTW.... "
I don't think so ..
I'm not saying its not farmers responsibility to clean up their mess, but trying to have no muck on the road whatsoever is completely unworkable as far as I can work out. Signage is one short term compromise (not a brilliant one), but is at least 'workable'
Building sites typically have more traffic and all day every day, rather than a 'freak' intensive harvest period a field may get for an hour or two (as outlined above), not that it makes any difference in law
Horses get to crap on the road and the riders don't have to pick it up (yet dog walkers are supposed to)?