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Frequency-based service

Practice Recommendations Organized by Use Case

Frequency-based trips

A frequency-based trip does not follow a fixed schedule but attempts to maintain predetermined headways. These trips are denoted in GTFS frequency.txt by setting exact_times=0 or omitting the exact_times field (note that exact_times=1 trips are NOT frequency-based trips - frequencies.txt with exact_times=1 is simply used as a convenience method for storing schedule-based trips in a more compact manner). There are several best practices to keep in mind when constructing GTFS Realtime feeds for frequency-based trips.

  • In TripUpdate.StopTimeUpdate, the StopTimeEvent for arrival and departure should not contain delay because frequency-based trips do not follow a fixed schedule. Instead, time should be provided to indicate arrival/departure predictions.

  • As required by the spec, when describing trip in TripUpdate or VehiclePosition by using TripDescriptor, all of trip_id, start_time, and start_date must be provided. Additionally, schedule_relationship should be UNSCHEDULED. (e.g., re-enforcement trips).