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.

It is true. At night a 70-year-old person is basically blind. They can't cope with oncoming headlights because their pupils take seriously minutes to make adjustments that a young eye can make in seconds. Old pupils don't open as wide as young pupils. Old eyes have only half the rod receptors a young eye has. These effects are already noticeable to people at age 50.

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.

> They can't cope with oncoming headlights [at night]

One of the reasons I stopped driving 20 years ago (~30) was because I have this problem. Made night driving much more stressful.

That'll be why it's all people half my age (I'm about 50) who are terrified of driving at night because they can't see properly, and I (and people my age) can read the number the guy in the car in front is calling on his phone, then.