My boss is a mean 77. And let me tell you, I've been in a car with him. HE SHOULD NOT BE BEHIND THE WHEEL!!!! He stops at greens, goes at yellows and reds. He would pull in front of others, my eyes closed ready for impact. I've seen him pull into the drive at work, not coming in the part you're supposed to, but right over the median into our parking lot.
I'm not saying all elderly people are like this, but a good majority are. I think they should be tested to weed out the bad from the good. Just as I believe that teenagers should be tested every year or so to make sure they still understand the rules of the road.