Do you go with your parent to the doctor? If not, can you call the doctor's office and mention your concerns, so the doctor is aware and can perhaps help your loved one realize that driving is no longer safe for him? If you can somehow have the doctor tell him that he should no longer drive, there will still be drama, but at least you won't have all of the blame placed upon you.
I recently went through the same thing with my mom. She was diagnosed with dementia 2 years ago, a week before she was off to renew her license. She of course felt that there was nothing wrong with her.
My mom failed the tests at first, passing only on the last try (I can't remember how many times you can take the written test, I think it might be 6?). Same with the driving test - failed all until the very last one, and the instructor happened to be an older gentleman that apparently was won over by my mom's tears.
One year ago, my mom had a neuropsych evaluation, and was told she needed to follow-up with a senior services rep that specifically works with elderly drivers to make sure they are safe. My mom never did this, because of course the doctor was crazy.
One year later, after 2 accidents where some phantom car apparently ran her off the road each time, getting lost a few times, running into mailboxes and the edge of the garage, and twice being pulled over for driving under the influence (she is also a prescription drug addict) and somehow having the officers take pity on her and not haul her away, her psychiatrist finally told her this August she was no longer allowed to drive. However, I had to take away her keys. That was really hard to do, there was a lot of anger and awful words said to me, but I just kept telling her I was following the doctor's orders. That was all I would say to her, arguing about it when your loved one is yelling at you doesn't help at all. Just keep repeating "doctor's orders" and remind yourself you are helping your loved one, not hurting him.
After that, my mom took too many drugs again and started drinking, ended up no longer being allowed to live in her home again, and is presently in assisted living until this Wednesday, when she moves in with me. I will be here to drive her where she needs to go, my brother took the car out of state to his place, and she has no idea how to drive my hybrid since there is no "key" (sensor fob only, safely hidden in my purse's deep compartment).
I wish you lots of luck, and lots of strength. If you can have a doctor say the tough words, it would be best. You will still have to deal with the anger and taking away the keys, but hopefully some of the blame will fall on the doctor. As previously mentioned, make sure there are other ways for your loved one to get around, so they don't feel confined. I think the loss of freedom to go where you want, when you want, is hard to accept, but hopefully you can put a nice spin on this, and mention that you guys will spend more time together going places? Not sure if that will help, it didn't help with my mom, but maybe for someone else it might?
Good luck. It will be tough, but you will be ok, just remind yourself this is for everyone's safety. And remember, "Doctor's orders!"
