I know everyone here has a 90 year-old relative who is as sharp as a fighter pilot but the fact remains that 85+ year-olds seldom have the reflexes, cognitive agility or perceptual acuity to drive safely.
I remember talking with a grocery store manager while living there as he looked for a missing car of an elderly shopper. He said he learned quickly not bother asking the model, or color of car because he said they rarely remember. He took the key fob and clicked until he found it, or found a matching car and tried the key.