Duplicate agency_ids across different agencies

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Karl Wagner

May 6, 2020, 6:23:54 PM5/6/20
to GTFS Changes
I've found that the same agency_id is being used by more than one agency.  For example, both the Des Moines Area Regional Transit Authority and Dallas Area Rapid Transit both use "DART" as their agency_id in GTFS static feeds.  Should there be some sort of authority that approves or issues agency_ids to avoid duplication?  Is there a naming convention needed to avoid duplication?  For example dart.tx.us for Dallas and dat.ia.us for Des Moines Iowa?  Maybe something similar to IANA is needed for agency_ids?

Anybody have any practical experience on how to handle agency_id collisions for multi-agency systems?

Stefan de Konink

May 6, 2020, 6:48:40 PM5/6/20
to gtfs-c...@googlegroups.com
Andrew Byrd the benevolent owner of gtfs.org initially wanted to use the
domain to assign unique feed_ids. That would allow producers to register an
unique feed_id and thereby have a custom namespace.

I think the best practise is to combine the feed_id and other properties to
form a unique combination (for an integrated feed), or if possible use,
unique tablespaces in a database.


Tim Millet

May 6, 2020, 7:06:59 PM5/6/20
to GTFS Changes

Hi Karl,


Within a dataset, each id field requires unique id values. However, unique id values are not required throughout different datasets.


MobilityData (mobilitydata.org) is currently projecting to build a database of unique identifiers, including agency_ids, to support the transit data industry on this issue. However, any data producer will still remain free to provide id values the way they want within their dataset.

Pascal RHOD (Kisio)

May 7, 2020, 10:48:35 AM5/7/20
to GTFS Changes
In navitia.io, we chose to prefix all feeds with a unique prefix to avoid those Id collisions.
This prefix is specified at the source level (ie. the URL of the feed) to keep it consistent.

Sean Barbeau

May 7, 2020, 11:19:26 AM5/7/20
to GTFS Changes
FWIW, Transitland does currently have unique identifiers for operators/agencies using a "Onestop ID scheme":

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