1. Total US population, and total deaths per year
2. Amount of miles traveled yearly.
Measure butt-in-seat hours.
If we aren't then you're just measuring the fraction of the population that drives (which is largely a reflection of wealth and demographics) which isn't really a measurement of the safeness of the roads and driving.
[1] https://en.wikipedia.org/wiki/List_of_countries_by_traffic-r...
Specifically in the US the limit is 26,000 lbs GVWR without a CDL. That is the gross vehicle rating cannot be over 26,000 lbs, even if it actually weighs less when driven.
I've always assumed that exceeding the GVWR is illegal but searches show conflicting results.
That said, I think people should be reasonably safety-conscious about vehicle maintenance, avoiding risky situations, and avoiding things that could sabotage the automatic-driving part of their brain, like doing other things at the same time that require their attention and their hands and eyes.
Be a passenger in a car with a driver you're unfamiliar with. Lots of people struggle with that and way overestimate the speeds the driver is going at.