I disagree with this principle. I’ll only speak of the US since it’s what I know.

Who decides what’s safe? How do they come to those conclusions? At least in the US, our speed limits are politically and financially driven as much as it is for safety. Identical conditions can have widely different limits depending on where you are and what state you’re in.

Similarly, there would be greater use of variable speed limits. A straight stretch of road is perfectly fine in my sports car at 110 mph with no other cars around. But if it’s congested, perhaps 40 is the right speed limit.

As has been pointed out earlier, towns in the UK can vote in a 20 mph speed? So the average citizen can decide what’s safe? This morning when I drove to the EDI airport, 20 mph was the fastest I could drive safely despite being the only car around? A similar road would have been 45 mph in the US. So am I just horribly reckless and lucky at home?

I’d contend safety is one consideration. So are politics, desire to discourage traffic using certain streets through calming measures, desire for the government to make money from fines, etc. It’s not random, but it’s not as scientific as you’re presenting either.

I’m not really interested in debating this issue; like I said, yall have your laws and customs and it’s my responsibility to follow those to the best of my ability when in your country. I’m only sharing my POV and experience because I’m fascinated when I see topics where our countries and cultures diverge so dramatically.