GTFS (General Transit Feed Specification) is an open format for describing stop locations, schedules, etc.
It resulted from a collaboration between Portland-based transportation company TriMet and Google in 2005.
To popularize and control the development of the format, the company Mobility Data was created.
More than a thousand transportation companies provide data in this format
to developers and companies.
The data are distributed as a ZIP archive with CSV files:
Especially curious to me is the GTFS-Pathways
format extension (
pathways.txt) describing the multi-level stations, transfers, and boarding zones.