I don't understand why people get hung up on the notion of "re-test" every X-number of years. The roads are full of drivers who drove to the standard for the duration of the test and know the standard required. Problem is, once they are behind the wheel by themselves they drive like utter lunatics with no regard for either their own or others safety, even basic road markings are too much trouble to comply with.
I disagree, these ''utter lunatics'' by your view are hardly the biggest problem on the roads, the biggest problem are the people who have no idea of the driving standard, or have no clue how the car works and behaves ( oversteer/udnersteer, inner workings of simple things like a gearbox or clutch, let alone what their wheels are doing, or how to reverse park), or are to slow/blind to drive (mostly elderly). Basically people who have no coordination at all, and are also rubbish at reading and anticipating traffic situations.
Personally I don't believe people who have rubbish control of the vehicle ( eg. have no clue what to do if it under or oversteers or how to properly recover from 2 wheels in the roadside, or hell, even park a car) shouldn't be driving. Same as people who are still afraid after half a year of driving ( sorry for my lack of empathy, but if you're somehow so anxious behind the wheel then perhaps you shouldn't be driving at all).
Do you think that they suddenly lost the ability or forgot how to drive within a few months/years OR simply have the mind-set that the rules don't apply to them? The majority realise they are doing something wrong but simply don't give a toss. If you put the majority back under test conditions they'd modify their driving for the time required to pass the test then carry on regardless.
You can teach almost anyone how to drive, what is much harder to do is change their attitude to driving or to other drivers.
The lack of traffic cars on the road to catch poor, irresponsible drivers is the problem. Safety cameras that rake in money but only force folk to adhere to the speed limit for 30-40 yard don't make drivers safer. All the do is hit the brakes everytime the satnav beeps.
They lost the physical ability, or never had it in the first place and somehow passed the test by having an easy route or being friendly or lucky with the examiner.
I disagree that the biggest problem is the youths, if you look at the accident statistics, accidents under young people have dropped a lot, and the biggest group is now the elderly (65+).
The problem is also generally dumb people who have no clue about their cars or traffic. It's mind boggling how many stupid/dumb bordering to mentally impaired morons are on the roads, and how they somehow manage to drive safely.
To be honest, I'm willing to go as far as saying, the UK is one of the safest countries traffic wise in Europe: There is no problem with road safety in the UK.