skills/network-accessibility-analysis/references/authoritative-sources.md

# Authoritative sources

- Last verified: 2026-07-19
- Review cadence: every 3 months
- Refresh triggers: OSMnx or r5py major release, GTFS specification change, or feed update

## Canonical sources

- [OSMnx documentation](https://osmnx.readthedocs.io/en/stable/) — street-network retrieval, modeling, routing, and projection.
- [GTFS Schedule reference](https://gtfs.org/documentation/schedule/reference/) — feed fields, calendars, times, and validation semantics.
- [r5py documentation](https://r5py.readthedocs.io/stable/) — multimodal travel-time matrix workflows.

Pin the OpenStreetMap snapshot or acquisition date and archive GTFS inputs. Record mode, cost function, departure window, network filters, snapping rules, and software versions.