Interesting debate, being one of the older generation, reasonably fit and still thinking that I'm capable of driving any day, anywhere in any conditions. In reality I know that my reaction times, concentration levels and all the other things that you need to be a good driver are less now than they were a few years ago.
How one is tested or assessed I don't know but I would willingly undergo some form of assessment if it was a legal requirement. The IAM do run an older driver assessment course but as yet have not attended.
Like most of us I see some terrible examples of older driver mistakes but they could be aged anywhere between 65 and 85 years old and maybe even older, so a one off assessment in this age gap is of no value.
Interestingly my next door neighbour (aged around 80) was involved in an accident on the M40 last year when he blacked out and crashed into the central barrier. Luckily no other person or vehicle involved and he was kept in Oxford Hospital overnight, at the hospital he was informed that his license was being revoked and therefore couldn't drive.
Six months later, lots of hospital tests with nothing too much wrong and a letter from his consultant stating as such, his license has been returned and he drives again, albeit only locally.
Reason for this story is that it would appear the medical profession have a large part to play in deciding whether or not a person is capable of driving but is it fair or right they should decide? I'm sure opticians see may elderly drivers who should not be driving but can they report you to the DVLA.?
I think the best judge of a drivers capability is probably their immediate family but who is ever going to report a case to the police or DVLA?
Some form of pro-active assessment would be good but it won't happen, an involvement in an accident is the only way the assessment would be done.