Streets, worn and laid out
Paths are worn by footfall and resurfaced in place; the town also lays out a street plan to its gates and crossings, builds it out of quarried stone, and drives it through the occasional building.
The simulation counts traffic per column, and above a threshold the ground becomes packed dirt, then gravel, then cobble, then setts, then asphalt, replacing the surface in place. Each era caps how far the ladder goes: the paving ladder is in the rules reference. Roads actually increase walking speed, so homes and plots compete on route cost.
Wear is not the whole of a street. Every five years the city redraws a plan: a line from the middle to each wall gate, each crossing and each civic door, the furthest built thing in each quarter, and a ring joining the spokes about two thirds of the way out. The route is chosen over walkable columns, preferring level ground, ground people already walk, and ground that is nobody’s house. From the industrial era streets are three paces wide and a grid of sixteen-pace blocks is laid outside the old core, so the medieval lanes stay where they were and the new districts come out square.
Planned columns are an intention, not a pavement: up to two dozen are open as roadworks at a time, builders lay gravel on them out of quarried stone, new plots may not overlap the plan, and a plot that fronts onto a street outscores one that does not, which is what makes the town come out in blocks along lanes rather than as a heap with gaps. Where something is already standing on the line, one building a year at most is bought out, pulled down for its material and re-commissioned off the line. It costs legitimacy and the chronicle records it.
The street plan of the metropolis is the footpath network of the hamlet, straightened only where somebody paid to straighten it.
In the code: crates/sim/src/city/streets.rs crates/sim/src/city/traffic.rs crates/sim/src/block.rs