If Joe Biden moved to Queensland, he’d need a formal letter from his doctor to keep driving his car, even if just for a quick run down to the shops or the pharmacy.

Otherwise he’d be fined up to $8000 and lose his licence forever.

So would Donald Trump, although the taint of his offence wouldn’t quite match the 34 felonies he’s convicted of in a New York court.

The law in Queensland requires every driver over 75 to carry a medical certificate attesting their fitness to drive. And it needs to be renewed every year (with a helpful reminder from the Department of Transport and Main Roads if you’re at risk of forgetting).

Why? Well. according to Dr DTMR, age reduces vision, muscle strength, flexibility and co-ordination – all of which affect how we drive.

All of these are liveable with modifications like wearing the right spectacles, driving an automatic, not manual, car or just adjusting your seat.

But here’s the killer, according to the DTMR: “Your ability to process information, and react to it, tends to slow down as you age. Driving under pressure can become stressful, giving you less time to react to changes on the road.

“When planning a trip, think about whether you are comfortable driving at peak hour, merging onto a busy freeway, changing lanes in traffic, travelling an unfamiliar route, dealing with a busy intersection.”

Our American friends might condemn that as further evidence of our “nanny state”, a criticism worth noting if their gun ownership of 120 firearms per 100 people got somewhere near our 14 per 100.

For no American state imposes such driving restrictions on its senior citizens. Nor, it is obvious, on its heads of state.

What we’ve seen play out over the past 10 days is living, breathing evidence of the process of ageing. It’s not an illness, just a natural process in which nature catches up with each of us in its own way.

Based on what we’ve seen of Joe Biden, he is in no condition to hold executive responsibility, let alone ultimate power. His stiffness of walking may be immaterial, as may his quavering voice, but the noticeable loss of sharpness, the struggle to harness thoughts, let alone the words to describe them should leave us all quaking in despair if, by some remote chance, he stays in the Presidential race and defeats Donald Trump in November.

His defiance denies him the opportunity to age gracefully and instead leaves him ageing disgracefully, grasping a job he arrogantly believes he is most capable of doing. His one achievement of this campaign has been to make Donald Trump appear youthful, stable and capable.

The western world is now well into an era where its voting and economic power sits with those classified as aged or ageing. Countries with voluntary voting (USA and United Kingdom among them) are seeing higher voter turnouts from older voters who carry a natural bias to those closer to their generation.

That will mean more policies to support the aged. Many (such as cleaning up the aged care system) are well overdue. Others such as the wealth shelters that protect the fortunes of those better able to provide for themselves are likely to escape attention.

None of this is designed as a critique of men and women of age continuing to be active in public lie and policy. But it is a claim for recognising that our limitations change as we age.

My observation over time is that we physically decline, losing stamina from middle age and while our wisdom increases through our 50s, 60s and 70s, , our mental acuity declines. Most of us are less open to new ideas, less quick to join the dots and respond rapidly.

Hence the restrictions on driving and pretty well anything that involves a motor.

Five years ago, I wrote a book, Has The Luck Run Out?, in which I posed the question of what is old? Based on what I had read of various strands of research, I thought the answer was 75. But I was still under 60 and speculated that I might think differently in five years or so.

And I do. But based on what I have seen in the contest for the world’s most powerful elected position, I doubt I’ll ever budge from thinking 78 is old and 81 is definitely too old.

(And a final note on this: Former US President Franklin Roosevelt, who had been crippled with polio for 25 years, was 63 when he died just as the western alliance had won the war in Europe and was months from finishing the war with Japan. Youth did not constrain him but nor might have age.)