Metrolink/SCRRA has codeshare ticketing from the Ventura County Line onto Amtrak Pacific Surfliner trains, but the VCL timetable lists the codeshare trains as their Amtrak train numbers/IDs instead of giving them a Metrolink train number as well.
Yeah – the train numbers that are mentioned in the route master are prefixed with an operator code to form an internal train ID that’s used in railroad backend systems (schedule management, authority control/train dispatching and signalling, train tracking and recording) to identify that train run on a given day of departure uniquely and unambiguously, similar to a headcode in the UK network. (FYI: I work on such a system at a US railroad, which is how I know these sorts of things.) That said, the analogy to a flight number falls down somewhat because train numbers in US & Canadian practice are not used as radio callsigns (the lead locomotive’s number is what’s used instead).
We’re talking about the same physical train being assigned two different refs by two different rail operators here – trains being exposed to GDS as a “flight” is a somewhat different case from the rail operations perspective, since the rail systems don’t ever have to deal with the GDS “flight” number for the train, but it’s very possible that the train runs on tracks of multiple operators, and even with crews from multiple operators, all of which can sell tickets for it.
Connecticut’s Shoreline East line (New London to New Haven) will sell you a ticket from New London all the way to New York City, with the Metro North commuter rail taking you from New Haven on. Though, tagging train numbers of the commuter rail seems wildly excessive. I only know this because I’m riding it to SoTM US
How embarrassing – I forgot that part of the train number is posted on a flipboard on the side of the locomotive. This is Train No. 268, pulled by the No. 911 San Carlos:
I long ago learned to ignore this sign and the conductor’s barely audible welcome/safety announcement when departing from San Francisco, which also mentions the train number. They also assign a two-character code to each service pattern – the actual thing we’re mapping as a route relation – but this is what only appears on the timetables and never on signs.
Let me know where I can surrender my railfan credentials.