Two things spring to mind here. Firstly, my wife's Granddad was a notoriously bad driver, mainly due to poor eyesight. After visiting us, we were always amazed that they never once had any trouble getting home again. Occasionally we would see them passing in the streets, and flash the headlamps and wave, but not once did he ever see us. Scary, very scary.
On a separate note, a few years ago I literally came within inches of killing an old couple in their old bean tin of a car with my wife's XJ. Thank goodness we were in a 40 zone and no faster. The old duffer driving was coming towards us, and had pulled on to the central hatchings to turn right (across us) into a petrol station. We saw him pull into the centre way ahead of us, and there was very little traffic around in either direction. Anyway, after staying in the middle for several seconds as we approached, he waited until we were within a few yards of him and then set off. Fortunately I was ready for him, and managed to swerve to the right in an attempt to go behind him. We skidded to a halt with the horn blaring away right next to him - he eventually saw/heard us and stopped too. We were both sat skewed across the centre of the road passenger side to passenger side and not enough room to open any doors. The old duffer's wife's face was a picture. He looked absolutely clueless, and clearly wondered where on earth we had magically apparated from, even though we had seen them for 20 to 30 seconds already. Dozy old *******. We would have crushed their bean tin car for certain.
Nearly a case of the last thing to go through his mind was his wife's.