I have menieres, though I don't drive, and from my understanding I have to get my doctor's ok to be able to drive. I'd say it's a common sense thing and depends on the extent of vertigo, from general off balance to full on drop attacks, especially if the latter come without warning.
It's to make sure they are safe on the road. If someone got a bad attack of vertigo or a sudden drop attack when driving the danger speaks for itself.
Maybe there is a time period of controlled symptoms like not having had a drop attack for so many years, I guess like epilepsy with being free from fits for so long.
I'd say the ear symptoms could be very distracting too - on top of fluctuating hearing loss and tinnitus I get things like weird frequency like switches where one side of my hearing shuts off randomly and I get a frequency like sound in my ears.
On a general note, so far so good with the methotrexate :) Had more energy this weekend than I have had a long long time and been able to get out and enjoy my birthday :) Feels so good! Up to 15mg weekly from this week so hoping it'll kick in on the pain soon!