The Welsh parliament has passed a law bringing down the speed limit on all residential roads and busy streets to 20 mph (30 km/h). Not everyone is pleased.
They just want to make money. They've covered the country with cameras and then they dropped the speed limit to a brisk walk. Breaking 20mph is almost guaranteed by accident, and those cameras are going to snitch.
This doesn't really apply because harm to a pedestrian during an impact isn't a linear scale.
There are sharp decreases in fatalities and permanent injuries, particularly to children who are often the ones hit in neighbourhood streets, below about 30 km/h so there's a strong incentive to have drivers travelling at speeds no higher than that to avoid child murder and maiming due to inattention.
Below those speeds, and given that people do often belatedly apply the brakes when they're driving recklessly there is a much weaker case for further reduction in speed limits. At least until car geometry changes again to make them even deadlier /shrug
shrug
I agree, it's a trade off. That's why reducing car usage is the most important thing. Making it less convenient to use a car, and more pleasant to walk and cycle are some of the ways you can do that.