Earlier quoted context omitted.
If I trained a child to drive, I'd be comfortable letting them drive at 6. I believe I was around that age the first time I drove (handling steering, with assistance on gas / brake). My memory is that the only difficult part was a lack of power steering on hilly terrain. Same age for walking around town unsupervised: the Japanese do and don't seem to lose many. My original point was focused on the technical feasibili…
And my point is that it's not just about experience-years, it's also about the breadth of knowledge. When driving, humans do not use just the experience acquired from looking at things from behind the wheel. They also use their general understanding of physics, of materials, of concepts related to visibility, traction, not to mention expected behaviour of other people and how to read face expressions.
E.g. the disaster that is the first major snowfall, every year, or automatic transmissions, antilock brakes, and traction control systems becoming standard
The human can only reliably be trusted to keep the car between the lines, stop appropriately, and occasionally make turns. Which is something much simpler to compete with!