*'''[https://developer.trimet.org/gtfs_ext.shtml TriMet Extensions to GTFS]''' - Includes fields for bike_policy_url, feed_id, realtime_feeds info, route_sort_order, and continuous_stops.
External Links== * [http://transitfeeds.com/ TransitFeeds.com] - An extensive collection of official public transit data from around the world, including GTFS, GTFS-RealTime and more. * [http:// en. wikipedia.org/ wiki/ General_Transit_Feed_Specification Wikipedia page on GTFS] * [http://www.appropedia.org/General_Transit_Feed_Specification The GTFS page on the Appropedia Wiki], which includes links to [http://www.appropedia.org/Open_Source_Transport_Informatics_tools pages on useful tools for working GTFS data]. * [http://www.apta.com/resources/reportsandpublications/Documents/APTA-Embracing-Open-Data.pdf APTA Policy Development and Research - Public Transportation Embracing Open Data] - APTA's discussion of the benefits and challenges of open data. * [http://onlinepubs.trb.org/Onlinepubs/tcrp/tcrp_syn_115.pdf TCRP Synthesis 115 - Open Data: Challenges and Opportunities for Transit Agencies] - A report looking at the benefits and challenges of open transit data.