While we're on the subject (kind of, and I know this is a touchy one) older drivers really should have to pass some kind of proficiency test at, say, 67-70 years old and every three years after. There are some lovely old folk round here but, Jesus, I really don't know how they haven't killed anyone yet.
I don't know the statistics, but I suspect that, while the occasional 'wrong side of the M-way older driver' gets lots of press coverage, less accidents are caused by older drivers than those, say, 40 or under, if insurance premiums are any guide. I realise that my reactions are probably not what they were when I held a rally license, so, I hope, I drive accordingly. 
There are many, many older drivers who are more than competent, probably the majority. But there are a significant minority who are dangerous. As time passes, and people live longer, we will have a lot of drivers into their nineties. Surely we must make sure they are safe to be on the road?
One can only compensate for slowing reactions, ie. leaving a bigger gap, braking earlier etc., for so long before we become overcautious and irritate other road users, thus becoming a liability.
I have more than a passing interest as it won't be long before I would be affected and, although I think I'd be fine at an actual driving test, I wouldn't fancy the hazard perception one.
