Part of the issue is that the speed limit often times dictates how the street is designed. In my city, the default speed limit for city streets was 30mph. Safe

Part of the issue is that the speed limit often times dictates how the street is designed. In my city, the default speed limit for city streets was 30mph. Safety advocates lobbied for and achieved lowering that limit to 25mph. The goal was not that cars would immediately all start driving 5mph slower, but rather to direct the city's traffic engineers to start designing the street layout to lower the 85th percentile speed by about from 30mph to 25mph.