Trying to be charitable to both arguments: - speed is obviously a factor, but there's a wealth of other factors. 90 on a clear highway with little traffic, and

Trying to be charitable to both arguments: - speed is obviously a factor, but there's a wealth of other factors. 90 on a clear highway with little traffic, and the driver is alert? Fairly safe. 90 while weaving between lanes, leaving little reaction time? Not safe. - drivers seriously overestimate their competence. Humans undervalue outlier events. This is the root of the stat about accidents occurring within a mile of home. That's why we have generally-lax enforcement of motorway limits but "strict" enforcement of urban limits in the UK. I'm not asserting that we've got it right here, but it looks more sensible in my eyes. Caveat: urban centres are increasingly adopting 20mph. I think there's a tacit understanding that people will drive at 27. When it was 30, they'd do 34, so that's a big increase in survivability.