National Transit Tracker

A single map that ingests public transport feeds across Sweden and keeps them moving in real time. The interesting part is not the map, it is everything behind it. Feeds arrive late, out of order, and sometimes not at all. Vehicles disappear and reappear.

Delay is computed continuously per line rather than sampled, and free text incident reports from public forums are matched onto the lines they actually affect. It is the same class of problem as network telemetry: high cardinality streams, missing and late data, unstructured text that has to be mapped onto a fixed topology.