From personal experience I have noticed elderly people tend to make more mistakes whilst driving. Signs and speed limits are also often ignored. I feel many people over this age would struggle to pass the legal requirement for driving on public roads were they to retake it. Giving them a new driving test would keep drivers more alert and aware of anything they had previously forgotten about road safety. This, and the fact that dangerous drivers would be taken off the road, would help improve safety on and around roads.
I welcome any and all constructive criticisms you might have, thanks