I have thought this for many years. There are many more cars on the road these days and driving conditions are definitely worse than when I passed my test. If it was the law, we would all know it was coming. Reactions, eyesight and physical strength generally decline as we get older and we are not always aware of it. I would propose the first retest at 70, then 75 and after that 80. After the age of eighty, I think it should be an annual test. There could be a two strikes policy for each test so that if you fail one test you get a chance to retake it. If a second test is failed, then you could be offered the opportunity of a course of lessons with the test at the end being the final chance, or you could decide that this is the time to give up driving. Public transport needs to be improved at the same time otherwise, sadly. there will be more tragedies like this one - there have been several like this in the past, unfortunately.