When we have encountered this, our parents voluntarily gave up their keys.
The first was my Dad, who was a very good driver, but one time had a minor accident that was his fault, with one of his granddaughters in the car. She thankfully wasn’t hurt, but he felt terrible. His health was failing at that point, so he must have realized it was time to let others take care of him. He was gone in just another year after that incident.
The next was my FIL, who never much liked driving anyway. He had macular degeneration, so let his wife do most of the driving during his last few years.
Then came my Mom. She could drive fine, but she used landmarks as her guide very often, rather than reading street names. She died in the town where she was born and raised, and then raised her kids. It grew A LOT over 80+ years. At one point she made a wrong turn and couldn’t figure out where she was anymore, because businesses had closed, and new storefronts had taken over. Thankfully, she pulled into a store lot and went inside and was able to call my sister, who spoke to the clerk to figure out where Mom was. She was a little over a mile from home. It scared her enough to get her to give up the keys.
MIL was the hardest, but at 93 gave up her keys. She’d had two fender benders in parking lots (church and grocery store) in 6 months time. Her vision was getting worse and her reaction time was slowing. When we offered to give her an Uber card account that we keep refilled, she realized it was just a phone call away to have someone take her where she wanted to go. Problem solved.
There still is a working car in her garage, but that’s for when her kids or caregivers are there and can drive her where she wants to go. She KNOWS she can’t see well enough to drive at this point. (She’s 97, and still lives in her own home.)
My wife at 83 doesn’t have that problem.
Her IPhone using WAZE permits her to find her way wherever she wants to go.
My dad always came across to me as a very good driver, because he drove our family everywhere, and he seemed to be able to drive forever without having to take a break, and I never felt unsafe. We drove up and down the East coast as kids, drove all the way across the country on our way to California where we would take a plane to his next duty station in Japan, and he drove us through a tour of Europe, and he seemed superhuman to me. He could just drive and drive. No head nodding. No weaving. He was like an iron presence.
We all slept in the back with the seats down, and so many times I would wake up, and everyone else in the car was dead asleep, but I could see the back of my dad's crewcut head, unfiltered Pall Mall cigarette dangling out the side of his mouth, radio on low, and green highway signs appearing momentarily before disappearing into the blackness of the road traveled behind us.
I felt completely safe in that car.
In his entire life, I never recall him ever putting even so much as a dent in the family car, never had an accident that I know of.
The only time I ever felt alarmed with him was when I came home on leave one time when I was maybe 19-20, and my dad called home one night and needed someone to pick him up because his car had been stolen. He worked in Cambridge, MA as an operations manager at a bank (this was his job after he retired from the Navy) and had stopped at a shopping center to get a pack of cigarettes, and when he came out, his car was gone. (this was about 30 miles from where we lived)
For me at that time, before GPS, driving into Boston was like Columbus sailing the Ocean Blue in 1492. There be dragons. I didn't have any experience, and Boston, with its aggressive, rude, unforgiving, nasty drivers, and byzantine roads that were, rumor has it, developed from old cow paths, was fearful terra incognita for me.
And Cambridge, on the perimeter of Boston, was just as bad as the core city.
But I dutifully jumped into my beloved 1966 Doge van that had a automatic shift stick that protruded from the dashboard, and drove towards the Fresh Pond Mall, a high crime area in the city of Cambridge where my dad was stranded.
I picked him up, and pulled back out on the road and entered an awful, hideous two lane traffic circle adjacent to the mall. (We call it a rotary, others may call it a roundabout)
It was the height of rush hour, and in 1978-79, it was absolutely clogged with cars. No quarter was asked from drivers, and none was given. It was not driving for people who were inexperienced navigating it, or who were faint of heart, and I was both in that situation.
When I got to the rotary, I could not get into the rotary. The rule of thumb is that the people in the rotary have the right of way so you have to yield to them, but with traffic that congested there was never an opening. And by God, people were damn well not going to leave a space or wave you in. I don't know how long I sat there at the mouth of the rotary, but people behind me began honking their horns at me.
My dad sized up the situation and said "Let me drive."
In the middle of this huge, nasty traffic snarl, I jumped out of the driver seat and ran around the van to the passenger seat and my dad took over. I watched in astonishment how when he got behind the wheel, not looking left or right, he just pulled into the rotary traffic in a horribly scary and perfunctory way!
I would have never been able to do that, and my dad knew it. He had been navigating that stretch every single day for years.
When I later mentioned to my dad that I couldn't believe how he pulled into that traffic, he simply said "You have to do it. You have to see them in your peripheral vision and not even turn your head. You can't make eye contact with the oncoming drivers, because they take that as a personal challenge and will make it impossible for you to pull in. So you look at them out the corner of your eye, and when you see the slightest opening, you look straight ahead and go for it."
I never learned that rule in Driver's Education.
My Dad was a high-functioning alcoholic for most of his life, and I never remember him driving intoxicated until he was older and we were all out of the house, but I didn't realize he was an alcoholic until I was in my late teens and early twenties, so I may simply not have been seeing it.
But when he reached sixty, it was clear his alcohol was taking control of him in a way it had not before, and I was living at home after I got out of the Navy and had to drive to various bars in the towns to find him and bring him home, which was sad and humiliating to me, because I hero-worshiped my dad.
That was very tough for me, having to go into bars and convince him to go home. My parents were close to divorce at that point (my mother had a lifetime of his alcohol abuse) and my entire family was very alarmed that he was going to kill someone, or himself.
We had a family intervention and he understood, entered an inpatient alcoholism program at a nearby hospital, and became sober. But he was a solid driver until he died at the age of 75.
My mother, however, was another story.
My dad was at sea a lot when we were kids, and my mom had to raise six of us all by herself, and it made her crazy. As kids, we fought like all families (even more so) but sometimes the physical attacks on each other would get too much for her in that enormous white 1965 Chrysler New Yorker with that huge 400 cubic inch engine in it, and she would stomp it to the pedal and accelerate to speeds of up to 100 mph as we cried in terror for her to slow down.
Her hair, nearly standing on end because we were driving her so crazy, would yell "I'm not slowing this car down until you kids behave yourselves!"
To which we would sobbingly assent to get her to slow down. He dangerous and scary driving was a lifetime experience. We used to call her behind her back "Old Leadfoot" and her seeming ignorance of road conditions or traffic was always alarming to us. When I was in high school, she was driving me over to Fort Devens to get a new pair of glasses, and as we navigated this curvy back country road in our 1972 Plymouth Cricket (a manual transmission) she was...knitting! While she was driving! I watched the unfolding road in front of us in terror as I stole quick glances at her behind the wheel knitting, and at one point the car began to drift towards the non-existent shoulder where there was a huge 6 foot high boulder. As the trajectory of the car began to point us inexorably at the large boulder, and it got closer, I said "Mom...Mom...MOOOOMMMMM! and she looked up over her granny glasses, steered back to the center of the road and went on knitting!
On a funny related story, back in the late Seventies when we had the gas crunch of 1978, mopeds became a big thing, and my dad purchased one. I have no idea why he got it, because he sure as hell was not going to ride it. One day in 1980, my mother wanted to take it out for some reason (she was maybe 50 years old at the time, and I never once in my life ever saw her even ride a bicycle!) so...she got on the moped, had my brother show her how to start and use it, and got my sister-in-law on the back, and off they went! (This picture below memorializes the "priceless" event!)

We lived on an extremely busy main road into town, and sometime later, we noticed that traffic was light to non-existent. We walked out to the road, and there she was coming down the road at maybe 15 mph on that moped with my sister-in-law on the back. Behind her was a huge caravan of cars being impeded by her slow moped! To this day, I can see all those cars behind her as if in a parade, her sitting bolt up right on the seat of the moped, her hair being pushed out sideways on each side by the airstream (as if it meant to turn her hair into airfoils to make her go faster) and her granny glasses on her nose!
My sister-in-law was so frightened she never drove with her again.
What made me decide to insist on driving if I went anywhere with her was an experience I had as she drove me somewhere in my father's large 1979 Chevrolet Caprice Classic. She was doing her classic "old granny driving" as I anxiously scanned the roadway ahead. Suddenly and without warning in the middle of a moderately busy roadway, she simply stopped the car in the milddle of the road and said conversationally "I don't feel like driving. Would you drive?" and opened the door and got out.
If you have ever seen the movie "Jurassic Park", there is a scene where the passengers are in automated vehicles (going through the dinosaur preserve) which you aren't supposed to get out of (for obvious reasons) and Jeff Goldblum's character (Dr. Ian Malcom, a celebrity hipster scientist) who, being divorced multiple times is always on the lookout for a future Ex-Mrs. Malcom) is flirting with Dr. Grant's girlfriend, to whom he is explaining "Chaos Theory"...
ELLIE: I'm still not clear on chaos.
MALCOLM: It simply deals with unpredictability in complex systems. The shorthand is the Butterfly Effect. A butterfly can flap its wings in Peking, and in Central Park, you get rain instead of sunshine. (Ellie waves her hand over her head, indicating that explanation went right over her head.)
MALCOLM: [laughing] Did I go too fast? I did a fly-by.
ELLIE: I missed it.
MALCOLM: Here. Give me your glass of water. We'll perform an experiment. [and tries to get a better look.]
MALCOLM: The car should be still, but that's okay. It's just an example. Put your hand flat like a hieroglyphic. A drop of water falls on your hand. Which way will the drop roll off? Which finger?
ELLIE: Thumb, I'd say. [Malcolm places the drop of water on Ellie's hand. It rolls off the back.]
MALCOLM: Ah ha. Okay, freeze your hand. Don't move. I'll do the same thing, start with the same place again. Which way now?
ELLIE: Let's say back the same way. [Malcolm drops the water again, and gasps.]
MALCOLM: It changed. Why? Because tiny variations... The orientation of the hairs on your hand...
ELLIE: Alan, look at this. (She says this nervously to her boyfriend Dr. Alan Grant, as Dr. Malcom is holding her hand in an intimate manner as he gazes suggestively into her eyes. Grant’s attention is outside the vehicle. He notices something and isn't paying attention to his girlfriend)
MALCOLM: ..The amount of blood distending your vessels... Imperfections in the skin...
ELLIE: "Imperfections in the skin"?
MALCOLM: Oh, just microscopic... Microscopic... That never repeat and vastly effect that outcome. That's...what?
ELLIE: Unpredictability. (Grant’s curiosity finally gets the better of him, and he opens the door of the vehicle and jumps out.)
MALCOLM: There! Look at this. See? I'm right again. Nobody could predict that Dr. Grant would jump out of a moving vehicle.
ELLIE: (getting out as well Alan?
MALCOLM: (talking to himself in an empty vehicle) And there's another example. See, here I am now by myself, um, uh, talking to myself. That's Chaos Theory.
That scene exemplifies exactly how I felt when my mother just stopped that car in the middle of the road and just jumped out. I suspect my mouth opened and closed a few times like a landed fish, but I scooted over behind the wheel and off we went.
Both my parents passed away before someone had to take the keys away from them. It has been 20years now since she died (he went five years before her, and they are both buried in Arlington National Cemetery) and I miss them terribly. But their driving behaviors still stick in my. mind, and make me laugh with pleasure at the memory of them! (Well, mostly pleasure)