When Are The Driving Days Over?

My family is very important to me. Just as when my children were young, now I am concerned about my elderly parent and in-laws.
We are at the crossroads of how to get my father-in-law to stop driving. In all my years of dealing with the elderly, somehow things don't always work out the way experts advise. And I'm one of the experts! So when are the driving days over?

My 88 year old father-in-law became disoriented this afternoon on his way to our home. He and my mother-in-law left home at 4:05 pm, were to pick up a pizza and be to our home easily by 5:00 pm. At 5:45, my husband left to look for them, thinking they may have had a flat tire or some other car problem. His parents arrived at 6:00 pm, shakey but none the worse for wear. I came to find out he had passed our street several times and gotten "lost" in a school parking area. Yes, it sounds preposterous but it's true.

In his own words, my father-in-law said " I think my driving days are over". If it's only that easy. I'll see it when I believe it.