We're working on live public transport schedules as the first step to public transport routing. Here is the helper web app that shows currently supported GTFS feeds in different countries and cities and helps to match bus/tram/train stops from OpenStreetMap.org with stops from GTFS: https://gtfs-osm-matcher.organicmaps.app/
If you are interested in public transport schedules in your city, please let us know about feeds for your place/country, and help by adding/editing stops in OpenStreetMap.org
@organicmaps I'm interested in improving OSM data in Luxembourg. Could you add the luxembourg data sources to this? they can be found in the Transitous feeds.
https://github.com/public-transport/transitous/tree/main/feeds
transitous/feeds at main · public-transport/transitous

Free and open public transport routing. Contribute to public-transport/transitous development by creating an account on GitHub.

GitHub
@Luke_Vader thanks, we’ll check it and add.
@organicmaps Amazing, thanks!
One question, what do I do if more then one ID references to the same stop? e.g. the german feed has a different ID from the Luxembourg one, but they are the same stop?
are semicolon separated IDs valid?
@Luke_Vader If they are from the different datasets use different tags like gtfs:ref:<lux transport agency> and gtfs:ref:<germany transport agency>
@organicmaps
Thanks for that clarification.
Sorry to bother you, but two more things:
1. The editor you host wants to create a tag "ref:gtfs" instrad of "gtfs:ref" which is incorrect by both your previous clarification and the OSM wiki (edit: i created a github issue)
2. shouldn't it rather be gtfs:stop_id:*=* ?
3. I taged a relation with gtfs:ref=[ID] but it does not show in your UI as correlated. Is it taking into account relations? (It was done 3 days ago, and your UI shows data from today)

@Luke_Vader The current implementation suggests the most popular tag for the area, but if you are starting from scratch, you can pick one you like. Just edit osm tag key if you don't like the one added by default. Maybe there's a bug in how the most popular tag is calculated.

Relation tags are not supported yet. Any help and improvements are appreciated!