How do you tell your old parent she shouldn’t be driving anymore?

Just for the record, I am an American, but i have been through this multiple times. I had to deal with this issue with my grandfather, my MIL, and my own mother. Each case is different based on the individual person. For my grandfather, he just wouldn't accept that he wasn't driving as well as he did when he was 17, so we just kept disabling his car and having him take taxis until he just realized he had an easier time with the taxis than his car and gave it up. With my MIL, she was a very narcissistic woman. We saw damage to her vehicle from her hitting things or going up on curbs but she refused to give up driving. We appealed to her narcissism and explained how we wouldn't want her to kill someone and have her name drug through the mud with a bad police photo of her being what everyone sees when they google her. It worked. For my mother, it was a little trickier because she had the mental ability but was just slowing in her reflexes, but by then we had options like Uber, and many of her grandkids were getting to the age that they could drive. We just explained that the kids needed the experience of driving, and that having her there to "teach" and correct them was better than paying a driving instructor. We also showed her that if she quit paying for a car and insurance, she would have more money to do other things, even after paying for any uber rides. She ended up teaching 6 grandkids how to drive, and then started teaching some of the neighbor's kids. While we didn't take her license away, she basically only still has it because you need a licensed adult to teach a teenager. I said all this to help give you ideas on how to approach it, as no one size fits all. I hope you don't have to go the official route, but it is better than confrontation if needed. Good luck !!