Some approaches to safe systems design aren’t reasonable. In particular, the idea that cars should never go faster than the speed at which a fatal injury might occur if there’s a conflict with a vulnerable road user is mostly nonsensical. That might work in a small city or town center (and the road has to be designed so the speed is self-enforcing) but many are advocating for this to be the norm throughout entire cities. That’s like saying airplanes shouldn’t fly higher than 10 feet off the ground in case they fall from the sky or that ladders shouldn’t be taller than 2 feet lest the user make a mistake and fall off. Some design ideas might create a perfectly safe system, but render the tool essentially nonfunctional.