https://visionzeronetwork.org/projec...nd-case-study/
Lowering the speed limits overall allow us to make changes to road design which naturally reduce speed of vehicles. This is a chicken and the egg scenario. We can't retrofit existing infrastructure until one parameter changes, the easiest being speed limits.
My wife is taking a proposal to council in December with Calgary's first entirely vision zero designed community, Rangeview. Interestingly, when they changed the design to be based on Vision Zero based design the economics made the community more profitable.
I'd love to see a more complete CBA regarding the overall spend differences of reducing the speed limits.