Differences between the GTFS Realtime and Google Transit implementation

This page describes the major differences between the official GTFS Realtime and Google Transit’s implementation of the specification in the following areas:

  • Ignored official specifications: These fields are part of the official GTFS. Google Transit ingests this data without error but doesn't proactively use the data.

  • Different interpretation: These fields include the parts of the official GTFS that Google Transit interprets differently than the GTFS definition of those parts.

  • Experimental support: These fields are experimental in Google Transit’s implementation. If you want to implement a new experimental field, contact the Google Transit team.

  • Google Transit-supported extension: This extension is not part of the official GTFS. The Transit-supported extension includes both public extensions and Google Transit-specific extensions. Any partner can send this information to Transit in their feed.

Realtime transit

The following sections document the major differences between the official GTFS and Google Transit's implementation of the Realtime transit feed.

Ignored official specifications in the realtime feeds

Some ignored specifications are experimental. To learn more, go to gtfs.org.

Table 1 lists the GTFS-defined fields that are ignored by Transit in the realtime feeds.

Table 1. Ignored official fields in realtime feeds
Message Ignored field defined in the GTFS Field type
message Alert image TranslatedImage
message Alert image_alternative_text TranslatedString
message Alert severity_level Enum
message Alert tts_description_text Proto
message Alert tts_header_text Proto
message CarriageDetails id String
message CarriageDetails occupancy_percentage int32
message Position bearing Float
message Position odometer Double
message Position speed Float
message Shape encoded_polyline String
message Shape shape_id String
message StopTimeUpdate (in TripUpdate) arrival.uncertainty int32
message StopTimeUpdate (in TripUpdate) stop_time_properties Proto
message TripUpdate trip_properties Proto
message TripUpdate vehicle VehicleDescriptor
message VehicleDescriptor license_plate String
message VehicleDescriptor wheelchair_accessible WheelchairAccessible
message VehiclePosition congestion_level Enum
message VehiclePosition current_status VehicleStopStatus
message VehiclePosition current_stop_sequence uint32
message VehiclePosition multi_carriage_details.id String
message VehiclePosition occupancy_percentage uint32
message VehiclePosition stop_id String

Different interpretation in the realtime feeds

Although Transit accepts certain GTFS fields, Transit interprets them differently than the GTFS.

Table 2 lists GTFS-defined fields in the realtime feeds that are either optional or required conditionally by Transit. For optional fields, the table shows whether or not the enum values are supported by Transit.

Table 2. Differently interpreted realtime feed fields
Filename Field defined in the GTFS Field type Required by Google Transit? Google Transit implementation details
message StopTimeUpdate (in TripUpdate) stop_id String Conditionally required

When a stop_id string is provided, it must meet one of the following conditions:

  • The stop_id string must be the same as in the stops.txt file in the corresponding GTFS feed.
  • If a different stop_id string is used, then the provided stop_id string must be a sibling or child string of the original stop_id string that's provided in the static GTFS. The corresponding stop_sequence field must also be provided.
message StopTimeUpdate schedule_relationship Enum Optional

Google Transit supports the following enum values:

message TripDescriptor schedule_relationship Enum Optional

Google Transit doesn't support the following enum values:

  • CANCELED—when it’s not for TripUpdate records

Google supports the following enum values:

  • CANCELED—only supported for TripUpdate records

Experimental support in realtime feeds

If you need support to integrate new experimental fields, contact Google Transit.

Google Transit-supported extensions in realtime feeds

At the time of publishing this article, no fields belong to this category. If you need any assistance, contact Google Transit.