I myself come from a background in network security which maybe colors my thinking, but there is a sort of quirk/feature that nobody ever argues for less security, only more. Basically this means you are always at the intersection of usability and and security. It is, however, usually clear what “usability” means in a given context.
So the question that lingers in my mind is this: how do you find the sweet spot for roads? The video says, and I agree, that people putting their convenience above the safety of others is an asshole. But how do you avoid the reducto ad absurdum that is mentioned AND THEN TOSSED OUT WITHOUT COMMENT where further decreasing speed always increases safety by some margin?
Where is the Pareto optimal point and how do you find it? If everyone goes 5kph, one guy a year is going to die. Are we really just trying to find maximum throughput per person per unit space? Is it maximal throughout with minimal infrastructure? What is the actual problem (generally) to solve here? There’s discussion AROUND the topic (about 2/3 through the video) but it’s all special case. Would be easier if there was a theme besides “hey go slower asshole”.