The only solid argument I can think of for not retesting those over 70, (an age I'm rapidly approaching!), is one of cost.

Granted young and inexperienced drivers do have proportionaly more accidents but these are not due generally to physical deterioration and the causes can be better addressed by education, restrictions for new drivers and tougher initial testing.

I know that my reactions are slowing down, my eyesight and hearing aren't what they were when I was 30 and nor is my physical flexibility.  I see no problem with taking a test every couple of years, if only for personal reassurance.

I took a council minibus test a few months ago, so I can drive for the Girl Guides, took just a couple of hours out of my day - there's no reason why a car test should take any longer.  If you fail to pass the driving test it means you aren't safe on the road and don't have the right to drive - I'm sure most right minded people would agree that is the way it should be.

So if the cost can be kept to an acceptable level what real argument is there for saying that we shouldn't check that those who have reached an age where it is known that physical and mental ability diminishes, are still capable of driving safely?