Add a trip in realtime

You can add a trip instance in realtime. Duplicate an existing trip prototype defined in the static GTFS data and schedule it at another time. To add a trip in realtime:

• Specify schedule_relationship as ADDED.
• Identify the trip by referring to the static trip and use the trip_id. 
• Specify a new schedule using start_time. It’s recommended that the start_time be different from the start_time of the original trip. All arrival or departure times at stops are copied from the original trip and shifted accordingly unless explicitly specified.

It’s possible to add a trip for both the exact_times trip and frequency trips cases. For a frequency-based static trip with exact_times set to 0, use schedule_relationship of SCHEDULED instead. The ADDED trips will also be treated as scheduled.

Added trips must not contain block transfers as it’s not possible to add a trip with block transfers in realtime.

Add with TripUpdates

To maintain reference to the added trip, the <trip_id, start_time, schedule_relationship> tuple must remain stable. A stop_time_update could be added to define predictions for the added trips.

Example code:

trip_update {
  trip {
    trip_id: xxx
    start_time: 12:34:56
    schedule_relationship: ADDED
  }
}

Add with VehiclePosition

To maintain reference to the added trip, the <trip_id, start_time, vehicle_id, schedule_relationship> tuple must remain stable.

Example code:

vehicle {
  trip {
    trip_id: xxx
    start_time: 12:34:56
    schedule_relationship: ADDED
  }
}

Add with ServiceAlerts

Additional trips don’t show up as part of the results. Instead, an additional service message is attached to existing trips. To indicate additional trips, specify ADDITIONAL_SERVICE in the effect field of the alert and indicate the appropriate informed_entity. The alert can be added at agency, route, or trip levels.

Example code:

alert {
  informed_entity {
    trip: {
      trip_id: "G5"
      start_time: "15:15:00"
    }    
  active_period {
      start: 1284457468
      end: 1284468072
    }
  effect: ADDITIONAL_SERVICE
  ...
}

This is how the ServiceAlerts information displays:

Changes to the GTFS specification

A GTFS proposal to support schedule_relationship=DUPLICATED trips was approved. We’re currently working on the new GTFS spec to provide DUPLICATED trips, which deprecates ADDED trips. After Google supports the changes, we’ll update this article.

If you already added support for DUPLICATED trip, refer to the migration guide.