Cool chart! Why does this end arguments about setting the speed limit though? Is 10% fatalities an acceptable level for pedestrian/cyclist collisions? Sorry if I'm not interpreting it right.
Oh! In that case I totally agree. The "I wanna go faster" crowd never seems to recognise that they're also in the "I think it's ok for more people to die" camp.
I don't disagree with you, however even this chart is probably biased because everyone drives at or above posted limits. Once you lower all the limits this chart will shift left, however, the slower you are moving the more reaction time you have and accidents that do occur are less fatal or destructive, so maybe in the end it will reduce accidents. I will be curious to see after a few months or a year of data.
While I haven't read the original source material, the labels for the chart are for collision speeds, not posted speed limits for collisions.
It's true that there's a large problem in many places with speed limit compliance, but this is primarily a problem of design - the streets encourage driving at speeds that are higher than the posted limit - and secondarily about enforcement, or lack thereof.
I agree that there are likely fewer accidents occurring at lower speeds as well, given that they are easier to avoid at those speeds. This is also a good argument for 30 km/h max speeds in urban areas.