The keys need to go!....help.

You can always his family doctor and talk to them about his license revoked. I went through something very similar with my Grandfather. He actually blacked out while driving and hit a street sign. My family got together and called his family doctor and talked to him on the phone for a few minutes. The very visit in there, his doctor said that due to circumstances he had to report a medical condition to the DMV and his license would be revoked. The threat being made that the doctor would go to the DMV was enough that he turned his license in on his own, for fear that the insurance rates would go up for my Grandmother to continue driving. Good Luck

I had to take the car from my 89 year old grandpa after he told me that he was driving down the street and looked up and was left of center. THAT was enough for me! I told him that I was taking his keys and that if he needed to go ANYWHERE to call me and I would be right there. He was pissed that I would do that to him but I explained to him that if I had been driving in the opposit direction and he hit me, how would he feel?! He still argued for months with me but I would mentally walk him through a car accident caused by him and he would agree with me that he shouldn't drive.
Say things like, "What if you hit someone head-on and they die and you survive, how would you handle that?" of "What if you go off the road and hit a tree and there is noone around to help you...."
It might not work for your Grandpa, but it's worth a shot! I know it took a lot of convincing for my grandpa, but he is now 94 and still mentally capable, he clearly understands why I took the car 5 years ago and I dont have to worry about him wrecking his car!
Good luck to you, I hope he understands!!

It's such a hard situation because you are taking away his sense of independence. AbusedMom is right. A doctor can have their license revoked, but be willing to be sensitive about this as it's a very hard adjustment.