Having the infirm elderly driving is funny/ scary/terrifying indeed! We're going through it both past and present. My Dad had to take over all the driving when Mom's mind went because she couldn't remember where she'd driven. But he couldn't bear the thought of not having a car in his late 80's even though he didn't have the range of motion to check behind while driving ("Well, I'll only drive where I have to go forward, I'll never back up"
) and his reaction time was slow ("I only drive in the middle of the day when the small children are at school"
He had "answers" for every protest. Finally the retirement home they were living in hounded him enough, I think that was after the bees nested in the roof of the car and stung someone.
Now my father-in-law age 92 is still driving despite macular degeneration, and all the problems above. His wife called the eye doc and pleaded with him to write that her husband could no longer drive. All he wrote was that he can't drive at night.
So daily he is driving at the time of day "when the sun won't shine in my eyes which is when I can't see." I firmly believe there should be more of a physical exam that accompanies driving tests which would include range of motion and more stringent testing of reaction time...and sanity. Of course then I might not pass