My family had to hide the keys from my grandpa when it was clear he was un-fit to drive.
That is why it was shocking to see him roll up in his Cadillac in his suit one day. Obviously he had made some extra copies.
It is a delicate subject. Taking the keys away from a family member, usually someone who is senior to you. But it is something that has to be done at times.
Alison from Safety Mom just attended the Lifesavers Convention and here is a piece she wrote about when to tell someone it is not safe to drive anymore.