I think it's worth referencing Sweden's Vision Zero [1] here, a project which aims to reduce all fatalities from automobiles to zero. They have a system of max

I think it's worth referencing Sweden's Vision Zero [1] here, a project which aims to reduce all fatalities from automobiles to zero. They have a system of maximum traffic speeds for different zones depending on what impact risks there are in those zones. For the zone where there are possible conflicts between pedestrians and cars the maximum speed is 19mph. The rationale for this is that below that speed the risk of a fatality from an impact between a car and a pedestrian is low but above that speed the risk of fatality rises very quickly. [1] https://en.wikipedia.org/wiki/Vision_Zero https://en.wikipedia.org/wiki/Vision_Zero