Part 4 — The road network: the map every mission runs on

Part 3 turned one truck's raw signals into an operating diary — driving, stopped, dark, refuelled. That diary was about the truck moving through space. This part is about the space itself: the reusable map a mission is planned against and judged by.

The map is deliberately shared. The same Douala port, the same Touboro border, the same stretch of asphalt between Yaoundé and Ngaoundéré serve every fleet that runs the corridor, so Korido curates each piece once and lets every mission reference it. The three chapters build that map from the ground up:

• Waypoints and road geometry — the atoms of the map: named geofenced places (each with an operational and a tight core radius), the enter/exit/dwell visits they record, and the curated road segments between them. This is also where the Tier-1 boundary idea is introduced — the reason only some places can anchor a comparison.
• Corridors — a corridor is a named, ordered sequence of waypoints. This chapter shows how its waypoint pairs resolve to shared roads when a mission is built, how an operator pins a preferred road per leg, and how inference runs the other way — from a pickup and a delivery back to a matching corridor.
• Route Guard — Korido's name for corridor monitoring. A mission's resolved roads and waypoint geofences are unioned into a single acceptance region, frozen at creation, and a conservative deviation lifecycle decides — through noise — when a truck has genuinely left its route.

A single principle carries the part: one geometry per road, curated once and shared everywhere. Fix a road in one place and every corridor and every mission that runs it is corrected at once. With the map in hand, Part 5 puts trucks to work on it.