How we move

The through-line here is that almost everything people experience as an inevitability on a street is a decision somebody made, usually decades ago, usually for a reason that no longer applies.

The early essays make the design case: speed, conflict and injury are outputs of geometry, and a community that wants different outcomes has to change the geometry rather than the signage. The middle of the series connects that to the economic argument, because street design is one of the few public investments where safety and commercial vitality point the same direction. The Paris essay is doing something different again: it is about the political cost of the change, and about what a city gets for paying it.

The most recent turn is from design to law. Mobility technology has moved faster than the statutes governing it, and Pennsylvania still classifies devices by category when the useful variables are mass, speed and operating capability. The e-bike question is the visible edge of a much broader regulatory gap.

What is unresolved is the local politics. The series is confident about what good street design looks like. It is less confident about how a suburb that has parked and driven the same way for fifty years agrees to change it.