# Paris Metro Lines — data notes

## Instance construction

The official instance is frozen and scoring never calls a live API. It contains 302 Metro stations; RER, tramway, bus and Transilien services are excluded.

Station names, coordinates and Metro memberships originate from public RATP / Île-de-France Mobilités station data. The archived source and attribution are recorded in the full JSON metadata. The official [Île-de-France Mobilités stop reference](https://data.iledefrance-mobilites.fr/explore/dataset/arrets/) is published under Licence Ouverte 2.0.

Named interchanges are collapsed into single station nodes. Existing edges follow the physical Metro topology, including the branches of lines 7 and 13 and the loops of lines 7bis and 10. Existing travel time uses 28 km/h plus 0.38 minutes per edge.

Candidate tunnels connect every station pair at most 3.25 geographic kilometres apart. Construction length is `1.08 × geographic distance`; travel time uses 45 km/h plus 0.32 minutes per edge. The resulting lengths and times are serialized explicitly.

The 13,031 scored demand pairs and their weights are fixed. Demand is synthetic but geographically informed, combining broad station activity, interchange strength, distance, modest major-hub priors and deterministic pair sampling.

The 2D coordinates use an arbitrary local origin and a longitude-corrected planar kilometre projection. They are provided for optimization and plotting; scoring uses the serialized edge values.

## Full JSON additions

The full JSON uses station identifiers instead of integer indices and adds:

- Station display names, latitude, longitude and Metro memberships.
- Existing-edge Metro memberships.
- Geographic map bounds, Paris boundary and Seine geometry.
- Source and generation metadata.