Inflammatory opinion incoming.
Issues with age and driving are an inverted bell curve IMHO. Lots of challenges with running out of talent when you’re young and running out of capability when you are old.
The weight stuff is so far proven to be a rumour started by the DF - If I recall correctly you were the chap who though the Chinese were going to hack our buses to stop the swing bridge in it’s tracks, but for my 2p, I’d be happy when 70 to have a medical every 3 - 5 years to ensure I am still fit to drive. As is already the case in many sensible EU countries, bendy bananas and all.
The amount of geriatrics I see on the road driving slow and dangerously is equalled by the amount of youngsters driving like twarts. They tend to get better though. Old people don’t, they get worse.
The reality is there is an age where you should just stop driving. That can be 65, 70, 80 or 90, depending on the person, their health and their reactions and awareness.
Edit - AFAICT they are just talking about imposing a test on what the eyesight should already be. If you have worsening eyesight you are already supposed to say so, and get a test, just people don’t. And those people are mainly older ones (the links already shared have the stats evidence for this). The 3.5T extrapalation just looks like it is because there is a stricter test for those driving 3.5T or more, so more older people will fall into that category, even if their eyesight means they can still drive a car. I think for the DF though that explanation can be complex for the hard of understanding.