We had huge problems over this. Dad had always been a law-abiding citizen till he got dementia, but telling him he was not allowed to drive and that he had no insurance didn't deter him at all. We took his keys while he was upstairs and fitted a crook lock. It took ages to get the keys though, because he knew that we wanted him to stop driving, so he kept them in his pocket most of the time.
We started to worry about Dad's driving before he had many other signs of dementia. He had an accident on his way home from a tea dance with his wife, and didn't stop. There was quite a lot of damage to his car, and his story just didn't add up. I couldn't understand why my stepmother hadn't made him stop, and why she didn't tell us about it for weeks. All we knew was that the car was away for repairs. Until that point, Dad had been a bit forgetful, but we hadn't thought much about it. He was very plausible, but from that time we started to question things more. My stepmother was in denial, but the CPN said that was quite common. It was me who went to the doctor about Dad, and it took a while before he took it seriously. I eventually convinced the doctor that we needed a scan, and after that everything fell into place. Dad has Vascular Dementia, and I suspect that he'd had a stroke when he hit the other car.
I used to have nightmares about him driving. The CPN made him a laminated notice that she put on the inside of his front door, reminding him that the doctor had said he was not allowed to drive, but he just kept hiding it! We let down the tyres, but he drove anyway. If we hadn't fitted the crook lock and taken his keys, we wouldn't have been able to make sure he didn't drive. I'd persuaded a friend who is in the police to come over to his house wearing her uniform, and tell him what would happen if he was caught driving, but he took no notice. He said the doctor had no right to tell him he couldn't drive, and then he denied ever having had an accident! After we'd disabled his car, we tried to persuade him to sell it and use the money for taxis, but he refused. We've only just sold it now. Shortly after we stopped him from driving, he had a bigger stroke, and pneumonia, and was taken into hospital. He moved from there to a nursing home, so he is safe now. He still tells me he has been out in his car when I go to visit, or asks me if I need a lift back!
It's very hard because it is the last bit of independence a person has, but it could cost an innocent person their life, so we have to take the hard decisions. My children have told me I will be giving up driving by the time I'm 70, and using my bus pass, so that nobody has to have the awkward conversation. I don't like to tell them that there are no rules that say you are safe until then!
I hope you can get this sorted. We found that there was no point in appealing to reason, because Dad just forgot the inconvenient bits, and then said we were trying to trick him out of his independence. It was very upsetting. Just remember you are doing the right thing: by the person with dementia, and by anyone in their path.
Love, Sue