Two system feeds, one agency. Can we send two static GTFS and RT-GTFS feeds?

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Joseph Raquel

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Oct 20, 2020, 7:45:02 PM10/20/20
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Hello- We have two different systems (two contractors) can we send two different static GTFS and two RT-GTFS feeds?  If so how is this handled?  Through the agency_id?

lai...@gmail.com

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Oct 21, 2020, 2:18:04 AM10/21/20
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Short answer, yes. New York MTA has 6 different  GTFS static feeds for buses, but 1 GTFS-RT feed for all of them.

Longer answer: what may concern some users (both developers and passengers) is the comparative quality of the data of the different systems.If one is lacking, you will likely hear about it.

Leo Frachet

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Oct 21, 2020, 8:05:14 AM10/21/20
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Hi Joseph,

You say you have two GTFS and two GTFS Realtime, are they matching one-to-one? Aka does your contractor A produce the GTFS A and the GTFS Realtime A, with the ids matching among them, and then your second contractor B produces the GTFS B and the GTFS Realtime B, with the ids matching among them?

If yes, then there is really no issue with that, since they are distinct. It's just two different sources of data.

I think that the NY MTA example is more complicated, since there is not a one-to-one match.

Leo Frachet | fr, en, de | Executive Director of MobilityData IO | mobilitydata.org


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Joseph Raquel

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Oct 21, 2020, 11:47:28 AM10/21/20
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Hi Leo- The two locations run the same but independent CAD/AVL systems (Avail) provided by Foothill Transit.  The two systems are separated because they are run by two different contractors, each monitor their own set of routes.  
We have not turned on RT-GTFS yet because i'm not sure if the static GTFS file needs to be combined or if i can have two separate static GTFS file sets.  Currently our HASTUS system creates a combined static GTFS.

So if a designate a unique agency_id for each location within the static and real time GTFS, will Google and 3rd party developers be able to handle the feed?  

Leo Frachet

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Oct 21, 2020, 4:42:52 PM10/21/20
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You have two options:
- either you have two distinct static GTFS and two distinct GTFS Realtime:
  - Pro: it's easier
  - Con: You cannot provide transfer time between the two static GTFS
- or you merge the two static GTFS into one and still have the two distinct GTFS Realtime:
  - Pro: You can provide transfer time between the two static GTFS
  - Con: The identifiers should not overlap. If two trips, one in each dataset, share the same trip_id, they will collide at the merging of the dataset. And prefixing the identifiers would break the link with the GTFS Realtime.

So you have to speak with your software vendor, and it depends of the assignation of your identifiers and your need for transfers.

Leo Frachet | fr, en, de | Executive Director of MobilityData IO | mobilitydata.org
l...@mobilitydata.org | +1 514 222 7204 | Montréal, Québec, Canada


harri...@gmail.com

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Oct 22, 2020, 8:04:39 AM10/22/20
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Are there many cases of having multiple TripUpdate feeds for one GTFS static field ? It is not something I have come across.

And is that a scenario that is implemented in most GTFS consuming applications ?

I would have thought the more common situation is that if you are merging static feeds, you also merge the associated real time feeds. 


Michael Smith

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Oct 22, 2020, 12:16:18 PM10/22/20
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I would encourage the combining of both the GTFS and the GTFS-realtime feeds so that client applications can see all of the routes for your system in a single place. There are a good number of applications where the user is provided with a list of routes, such as for a real-time map. If you provide two separate sets of feeds then the user would have to know which agency to use to be able to access the route that is of interest to them. The passengers of course don't know how the routes are divided between your two operators. Therefore this could be pretty confusing to the passenger.

Sean Barbeau

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Oct 23, 2020, 10:29:59 AM10/23/20
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Joseph,
Just to clarify - are these feeds for a single agency/brand "Foothill Transit" that is presented to the rider? In other words, if you populate agencies.txt in two static GTFS datasets will the records be identical? Or is more than one agency/brand presented to the rider (e.g., one per CAD/AVL)?

I agree that having a single GTFS and corresponding single GTFS-realtime feed is ideal and should be supported by all consumers, but it sounds like you'd need to build a GTFS-realtime feed aggregator to do this (an aside - I don't know of any out-of-the-box open-source tools that aggregate GTFS-realtime feeds, but in theory it wouldn't be too hard to create one based on some of the demos/utilities listed here). 

Outside of that, if you're stuck with two GTFS-realtime feeds it will depend on individual consumers if they prefer/support a single static feed or two static feeds that each correspond to a GTFS-realtime feed. If both CAD/AVLs are for a single branded "Foothill Transit" agency, I would think the single static feed would be preferable - otherwise, if the same agency is split across two static feeds the consumer would need some way for you to map that data together so they don't appear as two separate (but duplicate) agencies in the consumers UI. To my knowledge there isn't a standardized process for declaring that two agencies in separate static GTFS files are the same logical entity.

It would be great if consumers could comment which they support/prefer.

Sean

Sean Barbeau
Center for Urban Transportation Research
University of South Florida

Joseph Raquel

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Oct 23, 2020, 5:51:58 PM10/23/20
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Hi Sean- Yes, both feeds would be under a single Foothill Transit brand.  The agencies.txt files would be identical.  We currently use Nextbus and they get one static combined GTFS, but query two different servers, and combine the data all under Foothill Transit.
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