I wish there was open train data.
"Open train data" is a bit vague without mentioning where these trains might be, but I did find the London Tube schedule[1] in GTFS[2] format, as well as the bus schedule[3] also in GTFS format. Look for your city or country name followed by "open data" and you might find interesting datasets. In the UK the National Public Transport Data Repository (NPTDR) publishes a database of every public transport journey in Great Britain for a selected week in October each year[4] (only goes until 2011 though).
[1] Tube, scheduled trips: https://hash.ai/@tfl/tfl-gtfs
[2] GTFS is a CSV-based transit data format: https://developers.google.com/transit/gtfs/reference
[3] Buses, scheduled trips: https://data.bus-data.dft.gov.uk/timetable/download/
[4] NPTDR database: https://data.gov.uk/dataset/d1f9e79f-d9db-44d0-b7b1-41c216fe...