The organisation I am part of deals with this. I would be very careful about stopping older drivers full stop as some that we see that have been referred to us by various health professionals are still safe to drive, and retain the learned skills and still have the mental capacity to still drive.
We assess drivers with medical drivers (and drivers without medical conditions referred to us by the police).
At the current moment as has been said previously after 70 the driver has to reapply for their licence, but it is self regulating. The issue is that a lot has to be put on the GPs and Consultants when trying to determine if someone is safe to drive, for which they really don't have the time to do. Our department (and national organisation) aren't big enough to see them all.
Re: the Spanish model. We were involved in the European organisation looking into this (which the Spanish are part of) and with providers of these simulators and in the research we did it was found there was no real correlation between the simulators and a practical assessment of somebodies driving.
It is a difficult situation and we are constantly trying to find accurate tests that reflect a real life driving situation.
The other issue is the DVLA medical group are so far behind with medical enquiries that by the time they get the information it is out of date and if a older driver is told not to drive until the DVLA make their decision then they de-skill and can become dangerous.
Another issue we have is the lack of "after care" when someone is told to stop driving as a lot of the organisations that help keep people mobile after driving cessation means family members are reluctant to stop older relatives from driving as they do not want to look after them. Again our organisation are expanding into this area and again it is just too big for us but we can't help everyone.
It is a constant struggle to find the best way forward short of self driving cars!