Earlier quoted context omitted.
The visual acuity of a 70-year-old is roughly on par with a 20-year-old wearing dark sunglasses at night.
That's not actually true. Although it's bizarre because in the US 70-year-olds seem incredibly frail compared to 70-year-olds anywhere else.
The elderly can only drive safely under ideal conditions: sun high, not on the horizon, not at night, in clear weather where nobody is using their headlights.