I do think there should be drivers written tests required every certain number of years. Not just for the elderly but could also apply to the general public. Maybe every 10 years so that everyone can be updated on the newest driving rules. I see people blatantly forgetting/ignoring the rules and the city adding new types of traffic devices that were never in the drivers handbook when I got my license. The book changes each year and I think everyone could benefit from looking it over more than once in their lifetime. So I think it would be good to require driving written tests over the years and vision checks. As for an actual driving test that should only be required if your physical or mental capability has changed significantly probably at the request of a doctor.
I agree with what some people have been urging; testing everyone every 5 or so years. Not only to be able to check for physical impairments like poor eyesight, reaction time, etc.; but also as mentioned in the quote above to check people's understanding of the rules of the road. I know our city just installed a new traffic light that has a blinking green arrow. I had no clue what that was about. There was a traffic sign next to it that explained that "vehicles turning left must yield while
--> is blinking", but if I were turning the first time I saw that I may not notice the sign or not have time to read it completely, esp. if you were used to the solid green arrows and didn't realize that it blinking means something different.
I wouldn't even be against requiring people to take a refresher course every so often just to go over some of these new changes in the law. When I reffed for soccer, in order to first get our reffing certificate we first had an in-depth course talking about all of the rules in soccer as well as a lengthy written and practical exam. But then each year thereafter we had to take a refresher course which mainly covered any new rule changes, different things that FIFA had been talking about (such as the spirit behind some of the rules in order to interpret them consistently), and any rules that were either something that many refs missed or interpreted incorrectly. Then following the course there was a shorter written test for renewals. Maybe something like this applied to driving would make more people aware of the different laws yet wouldn't be so burdensome or expensive to renew your license either.
I could also see shortening that time between tests for both the young and the old to every year or two. For the young, the repetition would ensure that they get the experience of knowing what the rules are and how to drive correctly and safely. For the elderly it is more of a test to see whether physical changes that occur with aging aren't impairing the driver. I've actually been a little skeptical about the studies showing that elderly drivers are not dangerous on the roads. Most of the time, the studies only vehicles that are involved in an accident, but it may neglect to include reasons behind the collision. For example some elderly drivers know that their reaction times are slower, so tend to drive slower. If they are driving slowly on a highway (even if the highway has a minimum posted limit) the elderly driver may pose a danger to other drivers and may even be the cause of the accident even if their car was not hit. A person may not be expecting a car traveling at the minimum limit of 40 on a highway with a maximum limit of 65 (which means most traffic may be driving even faster at 70) and may tend to swerve out of the lane to avoid rear-ending the slow car. However if the person doesn't fully check the next lane, or hits their brakes too hard may actually get hit by a third car. And the issue may be exacerbated if one of the drivers of the 2nd or 3rd cars is young and therefore not as experienced as to how to handle situations like this; they may jerk the steering wheel too sharply or not properly check the next lane, etc.
But even if there were these mandatory tests, it wouldn't ensure that people would always drive the way they do during the tests. During the test, a person may, for example, leave their cell phone at home knowing they'd fail if the phone distracted them while driving. But then after passing the test, the person may go back into their bad habits of fiddling with the phone while they were driving. I know for my test, I made a conscious effort to keep my hands in the proper "2 and 10" positions at all times, but now I'm more apt to drive with only one hand on the wheel (esp. on empty stretches of highway where there isn't much issue with handling the steering). So even with the additional tests, you will still have the idiots that text and drive, apply their makeup (or shave their face, cuz guys are idiots too), drive too fast / slow, etc. But I think that the test would just help to reinforce the rules and may help to catch people that truly should not be allowed to drive for all our safety.