93 yo father. Stubborn. Mentally sharp. Still healthy but frail, poor eyesight, hard of hearing. Lives alone but has a good number of friends and likes to get out. Doesn't drive that much any more but still goes to pick up meds, groceries, doctor appointments. Everything within 15 minutes distance. Refuses delivery services, Uber, etc. Shouldn't be driving but it's his last vestige of independence.
Once I was no longer providing the full-time care, they quickly took away his ability completely and the live-in sister can't drive. Then he started becoming rebellious.
Do a search; this topic has many suggestions to try. Good luck to you and dad!
As his child, attempting to achieve the goal of keeping him and others SAFE may be both very difficult and possibly destructive in your relationship with him, which is SO important for him.
Have any medical personnel spoken to him about his driving? If so, can you flip the ball into one or more of the professionals’ courts?
If not, would he take an AARP Safe Driving course with you (or without you)?
When will his driver’s license be up for renewal?
Can you appeal to his sense of reasonableness and civic responsibility?
Show him statistics illustrating problems encountered by drivers over the age of 90? Might he be willing to make small payments to a younger friend for helping him out with a ride now and then?
As you point out, this sometimes becomes the last fragile vestige of “normalcy”, and especially painful and difficult to lose. Tough for him, and tough for you as well.
Poor eyesight and hearing could be enough, depending on how poor.
Has he had any fender benders?
As suggested, search for this issue as it's been covered many times.
If you're sure that he is unsafe behind the wheel, sometimes people do things like disabling the car so that they CAN't drive anywhere. And make excuses for why it's not fixed.
Good luck.