2015 Google Summer of Code Ideas

This page hosts ideas for the 2015 Google Summer of Code program, as discussed on the mailing list.

• GTFS-realtime validation tool - GTFS and GTFS-realtime have become dominant formats for open data in the transit industry. While the GTFS format has a GTFS Feed Validator, no such open-source tool currently exists for GTFS-rt. Due to the implementation details of the GTFS-rt specification, the GTFS-rt spec itself does not provide strong guidance for what data fields should be populated for particular use cases of the data. This proposal would implement a tool that takes a GTFS and GTFS-rt feed as input, and examines the GTFS-rt feed to determine if it properly meets GTFS-rt best practices, both those explicitly listed in the spec and those based on the needs of consuming applications. Sample rules to validate include:

  • stop_time_updates for a given trip_id must be sorted by increasing stop_sequence (failure)
  • Frequency-based trip_updates must contain trip_id and start_time (failure)
  • Timestamps should be populated for all elements (warning)
  • All timestamps must be in POSIX time (i.e., number of seconds since January 1st 1970 00:00:00 UTC) (failure)
  • vehicle_id should be populated in trip_update (warning)
  • If both vehicle positions and trip updates are provided, VehicleDescriptor or TripDescriptor values should match between the two feeds (warning)
  • If only delay is provided in a stop_time_update (and not a time), then the GTFS stop_times.txt must contain arrival_times and/or departure_times for all stops (not just timepoints) (failure)