Even with the caveats about limited data and untangling causation and correlation, the statistics are striking: the first year of a scheme in Wales where the speed limit on urban roads was lowered to 20mph resulted in about 100 fewer people killed or seriously injured.
I constantly encounter people who speed in my town in Wales. Then I meet them at the next light. It’s infuriating because they’re making the place more dangerous for everyone but for literally no benefit. The average road speed possible is below 20 mph so speeding just means a longer wait at the next junction.
These selfish fuckwits don’t appear to be able to grasp that though so things are still dangerous due to their childish twattery.