Service alerts at a headsign level

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Ryan King

Apr 26, 2024, 12:31:36 AMApr 26
to, Anatoli Plotnikov, Rui Song, Alex Mendes da Costa
Hi everyone,

Is there a specific reason why for alerts you can't associate them with a particular headsign? In other words, creating an alert for a specific line variant (eg it terminates at x station, or is an express train).

Have agencies/providers ever expressed interest in being able to specify alerts at this level of granularity?


Bodo Minea

Apr 26, 2024, 1:54:54 AMApr 26
I don't think that would make much sense because there's no such thing as a line variant in GTFS and a headsign based selector would be 'fuzzy' (eg. Based on a text that's not guaranteed to be a unique or direct identifier). Such a field would not only be ambiguous but also inconvenient and computationally expensive for a consumer to implement (eg. having to compare possibly long and complex internationalized text strings).

I believe the current way agencies go about doing this is by making the alert specific to the affected trip IDs (multiple trip ids can be attached to a single service alert). 

So there is a trip id entity selector that serves this purpose with enough granularity and that would be the standard way to go about it.

If for some reason you cannot uniquely identify the affected trips (eg. for frequency based or dinamically added trips) and you have route branches that are often affected by disruptions in different ways, an approach could be to split the route into two different route_ids with the same short name/color etc so that they look the same to users of a journey planner but will provide you with a simple differentiator for service alerts.

I hope this helps.

Best regards,

On Fri, Apr 26, 2024, 06:31 'Ryan King' via GTFS-realtime <> wrote:
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