This page lists data that has been made available from the rail and transport industry.

Network Rail

Network Rail Datafeeds, providing real-time train movement information from Network Rail's internal systems. You will need a reasonable level of technical skill to interpret the data.
The Sectional Appendix, containing detailed information of lines, routes, junctions and permitted speeds. This data is updated in June and December each year, an extract of the data in TSV and XLSX is here and historical versions of the Sectional Appendix are available for reference.
Working Timetables - schedules for passenger, empty passenger, freight and infrastructure trains.
Engineering Access Statement/Train Planning Rules, Data relating to planned engineering blockades and constraints on timetable planning.
Signalbox Opening Times
List of Level Crossings

Railway Safety and Standards Board

Railway Group Standards has current and withdrawn Railway Group Standards (the 'Rule Book'), Rail Industry Approved Codes of Practice (RACOPs), guidance notes and and Rail Industry Standards.

ORR Data Portal, including Signals Passed at Danger (SPADs), volume of freight movement, historical Public Performance Measure data, passenger train revenue and temporary speed restrictions.

Passenger timetable data from ATOC in Common Interchange File format
London Terminals data from ATOC, detailing the valid London station used when travelling from a particular station
Fares data from ATOC - see Fares Data

TfL Open Data, where you can sign up for access to numerous feeds, including live traffic camera images, real-time bus arrivals, Tube departure boards, station locations, a journey planner and tube disruption data.

Data.gov.uk details the route of the planned HS2 line. It is ESRI shapefile format. Licenced under Open Government Licence (OGL)

OpenStreetMap contains most of the UK rail network at varying levels of detail. Some stations are tagged with naptan:AtcoCode and/or a CRS reference, and some have routes associated with them. The Osmosis application could be used to pull nodes and ways from an OSM planet dump/extract.

Some of this data is fully open, other data is available for casual use but without clear licensing conditions.

SNCF Open Data is the open data project from French national operator, SNCF.
NS API for all Dutch trains is a great, simple API including stations, schedules, and realtime feeds.
Irail is a Belgian non-profit initiative with the aim of opening up transportation data.
eRail.in Indian Railways API.
DB Open-Data-Portal for open rail data in Germany.
SBB Open Data for open rail data in Switzerland.

Trafikinfo API for trains operating in Sweden provided by Trafikverket, the Swedish Transport Administration.
Järnvägsdata contains geographical data of railway infastructure in Shapefile format.

Finland has an extensive open rail data platform thanks to the government's open-data initiative.