Mapping train platforms subareas and markers

General talk Tagging general discussion
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Hello. For about one year now, there is a project on-going with NBMS/SNCB (the Belgian railway public service) about mapping railway stations. A next step is to map platform sub-area and sub-areas markers: meaning a railway platform that gives access to a train line but which is subdivided in 2 or more parts along the track, deserving the same train or not, typically numbered with letters: A, B, … I have some questions about the data models currently used and documented.

Mapping the marker denoting the subareas

  • A dedicated tag seems to exist: railway=platform_marker

  • see FR:Tag:railway=platform_marker - OpenStreetMap Wiki. The pictures in this wiki page are exactly what I mean by platform subareas in the Belgian context.

  • usage: only in France (416 items) and in Algeria (1 item)!

This seems a very nice solution, but, just a question: is another tag (railway=signal + railway:signal:stop ?) used outside France (and Algeria)?

Mapping the platform sub-areas

1) Use “railway:part = platform”

2) Use “railway=platform” for mapping individual platform subarea

It seems the common usage, but it brings several drawbacks:

  • info on the platform like height, surface, etc. can be duplicated, thus prone to maintenance errors

  • more complex for data consumption: for our use case of data consumption, we’d like to identify only one platform by railway stop, because we want to identify the access objects that exist on the platform. Of course, adjacent platforms can be merged when consuming the data, but this bring several fragilities and drawbacks (what we do of divergent tag values, are the adjacent platform really accessible for the travelers, …)

3) Use “railway=platform_edge”

The problem of one platform for 2 stops and the problem of the platform subareas is maybe solved by the usage of platform_edge.

The only thing is that it is mapped as a way (line), not an area. Usually, this line is then used for mapping the railway=platform area as a relation, with the platform_edge as one of the outer way. Seems widely used in Germany, but not in Belgium where the railway=platform as a closed way is preferred.

I’d like to hear here about what would be an appropriate data model for the train platforms, including these two open questions:

  • how to deal with the fact that a platform generally gives access to 2 tracks, e.g. track 1 and 2? Map one unique platform with ref=1;2 or map 2 separate platforms?

  • how to deal with platform subareas, like 1A, 1B, 2A, 2B? Map them separately? Superimpose platforms? Use railway:part=platform (area) and/or railway=platform_edge (line)?

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  1. Without understanding French, I find =platform_marker and =platform_section unclear. Aside from the Continental Europe use of them, there can be different train service, length / number of cars for each train service, each car, door number, and perhaps more positions. They need to be organized better. (Relatedly, this can be compared and coordinated with platform doors and gates) For =platform_section, this is confusing alongside sub-divided =platform_edge, when it seems to be for the queue line.
  2. As mentioned, there are different tiers of “parts” of a platform, from the side, through the section, down to each door. So railway:part=platform doesn’t work. Moreover, there doesn’t seem to be any other railway:part= imaginable, meaning it has limited usability. Theoretically, railway:part= would need a corresponding railway= in the first place, similar to how building:part= corresponds to building=. Their data hierarchy is different. railway= express different features, that are totally different; while building= are different types of similar-looking (usually enclosed) structures, with differing architecture and layout.
  3. Same for Q1 below. =platform should not be duplicated.
  4. Can you explain why they need to be areas? How do you define where the area ends inwards? In the middle of the island? On the inner side of the platform edge walkway? This has the same problem with dividing an island platform into 2 =platform .
    Q1. 2 =platform should not be added. This is arbitrary, unrealistic, and gives a false impression there are 2 back-to-back side platforms (it’s possible to have a wall dividing one, or they are 2 side platforms of different systems). What happens when there is a waiting room or shop in the middle: How should it be drawn, and which =platform does it belong to? =platform_edge is the proper choice.
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For the complete FR tag system for railway see FR:Gares ferroviaires - OpenStreetMap Wiki

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Thanks Kovoschiz.

About drawing multiple platforms on one platform, I agree that it is not a good choice. It causes issues if you want to count the access (or any features) on these platforms. But I saw it sometimes (maybe 1% or less than the Belgian train platforms).

But still, the subareas could be drawn with another tag. It would be used mainly for rendering the zones A and B in the platforms on custom maps.

=platform_section is not common from what I know. However, =platform_marker is clear to me: all Belgian train platforms are clearly signposted with blue platform markers. They are not related to the trains, but to the platforms.