My 91 yr old father-in-law over the past year has shown significant signs that his ability to drive safely is diminishing. He will frequently get lost, disorientated, and drives very slowly amongst traffic. His family has taken his car away, he is very upset and understandably so but his ability to drive a car safely and the safety to the public is a big concern. He has reacted strongly to having his vehicle taken away and is pursuing legal action to the car back. What can be done to discourage his continuing to drive? Thanks, for any helpful advise.