I’ve noticed that stumbling around for some questions about service=siding for railways that one user has changed some sidings into main tracks i.e. usage=main/branch under the justification that these are important for passengers (Changeset: 132981782 | OpenStreetMap, Changeset: 131667310 | OpenStreetMap).
The justification @DaveF gave is that these are main tracks because they’re intensively in regular passenger service which is different from how I know it in that passenger use doesn’t matter, only that trains explicitly need to request to enter these trains alongside the fact that trains have to slow down to enter these (and for further notes, Dave also put in a complain in the Wiki about the definition as on the Wiki).
The one true edge case where I’m in favour of treating both tracks as the main tracks is when both tracks are unidirectional (e.g. signals are placed in only one direction) after splitting from a bidirectional track (so there is main and a minor track but rather two main tracks) but this also is something I’m unsure of (example).
Relatedly, I also remember a changeset but I’ve checked many other places where “German rail enthusiasts”[1] supposedly mapped and the practices are the same as in Germany, apparently.
As a newish mapper but a 23yr driver on the railway. My definition would be passing loops are integral to the normal operation of the railway and diagrammed movements, sidings are only used for storage and shunting purposes. Passenger use is irrelevant for loops as you say, but permission is not required other than the normal clearance of the controlling signal.
Some things to note: Tagging can sometimes be a bit inconsistent with real world use (in this case, it’s siding in the American definition, not in the British definition) so a serivce=siding can be used to be both by passenger service and for temporary storage (that’d be service=yard).
In addition, by “request” I don’t mean some sort of “permission” but some sort of active involvement (mind you, I also have troubles to explain it properly).
What I meant is that you can determine which tracks of a station are through tracks and which aren’t by the layout of the points. This, as you know, primarily affects driving speeds since diverting points, thanks to the curve, must be driven at a reduced speed compared to straight points and trains which have no need to enter these passing loops will drive with straight points to preserve their speed.
Furthermore, the definition by both @DaveF and @Richard become a problematic when you look at the (generalised) real world usage, most notably most HSR stations which have four tracks (on a double-tracked railway) but platforms only at the outer tracks. Are these usage=* because they’re regularly used by passengers (especially because trains have to enter these tracks because it’s the only way for them to serve passengers in the first place) or service=siding because they’re at the end passing loops (just one which happens to be important to passengers)?