Time to take grandparents keys

My parents came to visit for several days earlier this month. My mom’s memory is starting to go. Dad seems to recognize the severity of it, mom only a little bit. She doesn’t understand why dad got a message to her doctor asking that the doctor test her. I know she does a lot of their driving. I asked dad if he was comfortable with her driving and he said yes, why wouldn’t I be fine with her driving? Now I need to figure out a way to see if her driving really is fine for now.