only experience i have of this is when my late partner was nearing the end, his wish was to spend as much time as we could at a special place 150 miles away, one Friday evening after finishing work and packing the car we set off as usual, me driving, I remember nothing about the journey from 5 minutes in till we reached our destination almost three hours later! I had driven down motorways, dual carageways, single track country lanes, over traffic lights and roundabouts, yet to this day do not remember the journey. my Partner asked if i was ok when i stopped the car, apparently i said yes why, and he replied because i had not said a word the whole three hours! oops!
I always drove with music on and the window open, and he apparently had tried conversing with me too, so when one dissociates there is little i feel can be done to stop it, though sweets can help stop it starting so too can plenty of rest beforehand.
i only drive a mobility scooter now, so the roads are fairly safe.