In my opinion some of this is simply due to how congested built up areas are today. It's genuinely hard to get up to 30 in a city or any populated area in the UK today, and most cities in the UK now have 20mph speed limits when there's likely to be pedestrians around.

It's pretty hard to kill people if you're driving under 30, and anywhere people are driving in excess of 30 it's not that populated and cars these days are pretty safe unless you have a head on collision at significant speed.

That and the speed limits are actually enforced, at least significantly more so than they seem to be here in California:

- Lots more speed cameras

- Average speed cameras especially make a huge difference vs spot enforcement

- Tolerance for enforcement is normally 10% rather than 10 mph (i.e. 30 limit means no more than 33mph rather than no more than 40mph)