note that it says they are "considering" it, they consider a lot of crap that never happens, trial balloons get sent out all the time on nutso ideas to see what happens.
I always thought that a tractor had to be licensed to be on the road anyway, they are on the road with other people and they are big, and they do represent a traffic hazard since they only go about 10mph.
The ones around here are pretty considerate though, they will pull over and let cars pass, but there's always that one jerk.............................