If people are ignoring the speed limit, you turn to infrastructure changes so people drive slower, eliminating slip lanes, no 5 lane roads in ‘walkable’ neighborhoods, or if you do add in pedestrian islands, etc.

If the focus is on road deaths, why bring up the red herring of cyclists and pedestrians? Pedestrians aren’t killing people, cars are.

To your point about cars from the 50s, they even talked about how cars today are bigger, faster, and higher (this last especially kills many more peds).