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 wonder what the optimal speed is to maximize speed and flow while minimizing accidents.
If it’s mixing bikes, pedestrians and cars? 30kph is about the maximum safe speed for cars because of the maximum speeds of bikes, and even then they’d need to be on separate roads