Class GTFSRealtimeTripDescriptor

The direction_id from the GTFS feed trips.txt file, indicating the direction of travel for trips this selector refers to.

Linkage to any modifications done to this trip (shape changes, removal or addition of stops). If this field is provided, the trip_id, route_id, direction_id, start_time, start_date fields of the TripDescriptor MUST be left empty, to avoid confusion by consumers that aren't looking for the ModifiedTripSelector value.

The route_id from the GTFS that this selector refers to.

The relation between this trip and the static schedule. If a trip is done in accordance with temporary schedule, not reflected in GTFS, then it shouldn't be marked as SCHEDULED, but likely as ADDED.

The scheduled start date of this trip instance. Must be provided to disambiguate trips that are so late as to collide with a scheduled trip on a next day. For example, for a train that departs 8:00 and 20:00 every day, and is 12 hours late, there would be two distinct trips on the same time. This field can be provided but is not mandatory for schedules in which such collisions are impossible - for example, a service running on hourly schedule where a vehicle that is one hour late is not considered to be related to schedule anymore. In YYYYMMDD format.

The initially scheduled start time of this trip instance. When the trip_id corresponds to a non-frequency-based trip, this field should either be omitted or be equal to the value in the GTFS feed. When the trip_id correponds to a frequency-based trip, the start_time must be specified for trip updates and vehicle positions. If the trip corresponds to exact_times=1 GTFS record, then start_time must be some multiple (including zero) of headway_secs later than frequencies.txt start_time for the corresponding time period. If the trip corresponds to exact_times=0, then its start_time may be arbitrary, and is initially expected to be the first departure of the trip. Once established, the start_time of this frequency-based trip should be considered immutable, even if the first departure time changes -- that time change may instead be reflected in a StopTimeUpdate. Format and semantics of the field is same as that of GTFS/frequencies.txt/start_time, e.g., 11:15:35 or 25:15:35.

The trip_id from the GTFS feed that this selector refers to. For non frequency-based trips, this field is enough to uniquely identify the trip. For frequency-based trip, start_time and start_date might also be necessary. When schedule_relationship is DUPLICATED within a TripUpdate, the trip_id identifies the trip from static GTFS to be duplicated. When schedule_relationship is DUPLICATED within a VehiclePosition, the trip_id identifies the new duplicate trip and must contain the value for the corresponding TripUpdate.TripProperties.trip_id.