Duplicate agency_ids across different agencies

[Karl Wagner]

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]

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.

--
Stefan

[Tim Millet]

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)]

Hello,
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]

FWIW, Transitland does currently have unique identifiers for operators/agencies using a "Onestop ID scheme":

https://transit.land/documentation/onestop-id-scheme/

Sean