For sure older drivers must indirectly cause accidents too. They pull out too slowly in front of people, they don't move with the flow of traffic which causes slowdowns, and they swerve into other lanes without turn signals. None of these may cause accidents with them, but can cause other people to end up in accidents because of the unpredictability.

I fully support more frequent tests for people whose cognition is declining.

I actually also support more frequent tests for everybody because there are a lot of people who should NOT be allowed to drive just because they're so bad and/or dangerous. Driving is a privilege, not a right, which comes with very serious consequences when done poorly.

Not sure I agree with both parts of your premise, there. Young drivers can pass their tests, and then on the first day that they have their license, go out in some Lamborghini supercar unsupervised on the motorway, finances allowing. It encourages a 'I have this bit of plastic, I'm as good as anyone' mentality; together with the general impetuosity of youth, you get the risky, accident-causing behaviour.

Compare that to a motorbike license - pass driving theory and CBT, and then a practical test, and you get the bog-standard licence to ride a chicken-chaser moped. You can then work your way up the licences, with minimum age requirements and time for holding each, until you have access to the big bikes, finances allowing. Make car drivers do the same, that'll cut down on the risky behaviour and the scale of the accidents that they could cause.

Admittedly, about the shittiest car that you can buy now will still do a hundred miles an hour, so you'd need some artificial limitations on power and which roads you can use..

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1056066/how-to-get-a-motorcycle-licence.pdf