2 ms·
> Doing 30mph instead of 20mph increases the chance of death for pedestrians from 5% to 45%. What is this metric supposed to imply though? We obviously have ro
by mehrdadn 8y ago
> Doing 30mph instead of 20mph increases the chance of death for pedestrians from 5% to 45%.
What is this metric supposed to imply though? We obviously have roads with limits above 30mph already, so clearly decisions aren't made based on merely chance-of-death-assuming-a-collision being too high.
- mprev 8y agoThey’re based on chance of collision with a pedistrian and, in the UK at least, on that stretch of road’s history of such incidents. So the figure shows that if there are more pedestrians likely to get in the way of your car then you should drive more slowly if you care about not killing those people.
- NeedMoreTea 8y agoThe biggest problem with UK limits is when they reduce a limit for an unrepresentative peak in accidents. When the figures regress to mean next year or two it's taken as proof the new limit was correct. So we slowly deviate from the 85th percentile rule, and get weird stretches of dual carriageway at 30 or 40 with a speed camera in the middle.
- adrianN 8y agoThis metric is supposed to imply that "it's only ten over" is not a valid excuse to speed in residential areas. Unless you assume that 20mph limits are just there for fun and not because it's an area where it's likely that a pedestrian crosses the road unexpectedly or where you share the road with cyclists.
- mehrdadn 8y agoI guess what I was trying to get at was that you need to also consider the likelihood of collision in the first place. I'd assume that's also higher in residential areas -- not sure if it's just me, but I think that would sound like a far more compelling argument than just considering the chance of death assuming a collision.