Slope signals

[Anasmasuris]

Hi, I'd like to ask whether any country has already implemented tagging for slope signals, which inform about the incoming slope of a track? Eg. in Poland tram tracks it's shown like this:

The number inside describes the slope in ‰. I'm wondering which of the railway:signal:* templates should be used in this case. For the number, I think it should be caption.

[hiddewie]

Belgium has signs for slopes (https://wiki.openstreetmap.org/wiki/OpenRailwayMap/Tagging_in_Belgium#Signalling, gradient sign) but no tagging is documented or implemented as far as I am aware.

[besentv]

Switzerland has these, too. But there isn't any tagging either: https://de.wikipedia.org/wiki/Neigungszeiger#Schweiz

[hiddewie]

Nice. The same wiki in Swedish (https://sv.wikipedia.org/wiki/Lutningsvisare) shows Swedish, Slovenian, Spanish, Slovakian, Chinese, Japanese and Austrian signs as well.

[Anasmasuris]

As far as I am aware, it's common practice to have those, yet there isn't an implemented tagging scheme. I asked that since none of given categories in https://wiki.openstreetmap.org/wiki/Tag:railway%3Dsignal in my opinion fit the description of the slope of a track

[besentv]

Germany doesn't have them... 😂 I think you can just invent a new one?

[wolfy1339]

There are similar function signs in Canada,
they don't display a particular grade percent, the signs are heavy grade or mountain grade,
Heavy grade >= 1.0% < 1.8% on a distance of 2 miles or more
Mountain grade >= 1.8% (any distance)

Maybe a generic category for warning signs should be added?

[hiddewie]

Given that this is a specific type of signal, we could create a tag category specifically for slope/incline/gradient. I like the term slope (wiki: https://en.wikipedia.org/wiki/Slope).

Tagging proposal:

• railway:signal:slope: country-specific signal value
• railway:signal:slope:slope: slope in per mille (‰), decimals with .. Positive values for upwards slope. 0 for flat. Negative values for downwards slope. Example: 7.
• railway:signal:slope:distance distance in meters, example: 35052
• railway:signal:slope:caption: (optional) actual text on the signal, example: 7;35052

Example image: https://de.wikipedia.org/wiki/Neigungszeiger#/media/Datei:Neigungszeiger_GBT_S%C3%BCd.jpg: slope signal on south entrance of Gotthard Base Tunnel.

[wolfy1339]

But this is about the signal, and the signal does not have an incline.

I think you misunderstood. I suggested incline:caption for the signal itself, and incline on the way

[Anasmasuris]

The incline:caption wouldn't differentiate enough the shape and thus the overall information given from the sign - for example both 5;1200 would describe the track having 5‰ slope for track, but it won't show, whether the track goes up or down

[hiddewie]

Yes just the caption is not clear enough. Same as speed signals, the caption could be 4 while the speed would be tagged as 40.

So I propose tagging both the caption, and the numeric incline value.

As tag I still think railway:signal:incline:incline would work, even if it looks a bit weird. Same structure as railway:signal:speed_limit:speed.

[entbert]

Given the tag https://wiki.openstreetmap.org/wiki/Key:incline incline exists, we should maybe name the category above from slope to incline, and allow values using % and ‰ units as well.

In my opinion, the fact that the incline key exists should be reason for us to not name the signal type incline. Otherwise the key railway:signal:incline could be misinterpreted as the incline of the signal itself (as with the keys railway:signal:position and railway:signal:direction). So I think railway:signal:slope and railway:signal:slope:incline would be better. Compare with our use of railway:signal:speed_limit (not speed!), but railway:signal:speed_limit:speed.

[Anasmasuris]

True, I haven't thought that way. I agree with above

[Anasmasuris]

Apart from slope:slope part, it seems quite logical. Maybe we could use already existing keys such as incline, since it's worldwide in use? But it looks good I think.

I'm not aware of other cases, but in Poland railway lines, there are two types of slope signals, depending on railway line's electrification. I assume it could be differentiated by the main key railway:signal:slope=*?

source: https://www.plk-sa.pl/files/public/user_upload/pdf/Akty_prawne_i_przepisy/Instrukcje/Wydruk/Ie/06_Instrukcja_Ie-102-od_2025-05-20.pdf

[Anasmasuris]

Alright, so up to this day, we could have the following tagging scheme:

• railway:signal:slope
• railway:signal:slope:incline
• railway:signal:slope:distance
• railway:signal:slope:caption
• railway:signal:slope:form

I think that if we were to implement those, they should be rendered in the Infrastructure layer.

[entbert]

I wanted to write a wiki page for Key:signal:railway:slope, but now I am unsure how the incline subkey is meant to be interpreted. Should positive/negative values be chosen relative to the OSM way or to the direction of travel? The former would be more consistent with other tags and the existing Key:incline while the latter is more intuitive and seems to be what is implied by the Polish AT-3/4 tram sign documentation.

[Anasmasuris]

When I was documenting this tag, I had a similar idea in my head as it exist for speed now, being: When I see the sign, I expect the state.

This means, while driving/conducting, seeing the sign with eg. 2,5% (the slope down), the incline of the track from that point on is -2,5%. This is described on wiki: https://wiki.openstreetmap.org/wiki/Key:incline#Tagging_based_on_traffic_signs

[entbert]

You are right that this is consistent with the road sign tagging. I guess then we should do it like that too.

[entbert]

Another question would be on signs like these used in the UK, which are placed parallel to the tracks and show the inclines in both directions. I see these two options:
(Example situation: We are in a valley where the track rises 1 % in both direction, i.e. the gradient sign is V-shaped)

• Option 1
  railway:signal:slop:incline:forward = +1% (rising when moving away from the sign in the direction of the OSM way)
  railway:signal:slop:incline:backward = +1% (rising when moving away from the sign in the opposite direction of the OSM way)
• Option 2
  railway:signal:slop:incline:before = -1% (the OSM way moves down on the section of the way before the sign)
  railway:signal:slop:incline:after = +1% (the OSM way moves up on the section of the way after the sign)

Option 1 would probably be more consistent with the above.

[Anasmasuris]

https://wiki.openstreetmap.org/wiki/Tag:railway%3Dsignal#Multiple_signals_at_the_same_location - well the first one would be suitable with the presented way of tagging signs at the same node. Similar to how maxspeed:forward i maxspeed:backward is handled

[TheSikal]

I've created slope signals for Belgium and adding some data with this changeset.

I've also added slope category to Signal Categories template.

[hiddewie]

Based on the documentation and tagging discussed above, I started a pull request integrating the signals into the OpenRailwayMap: #806

[entbert]

I have now written up the wiki page at https://wiki.openstreetmap.org/wiki/Key:railway:signal:slope.

Feel free to improve it.

[entbert]

Some further points I noticed when writing:

• As inclines can be stated in different units (usually ° or %), I would suggest not leaving out the ‰ as currently documented in the Spanish tagging.
• Maybe less urgent, but I would say the same for the distance value and metres, as the default unit in OSM for distances is km.
• Finally, as the distance subkey is still unused, what do you think about changing it to length? I am not a native English speaker, but "distance" sounds to me as if the track section with the respective gradient starts only after that distance, while "length" is more clear to me. (This would also be more in line with the existing Swiss tagging which I discovered only now (used exactly once).)

[hiddewie]

Nice find for the Swiss signal (https://www.openstreetmap.org/node/12000264528). It uses railway:signal:incline, not railway:signal:slope. Maybe we can retag it and redocument the tag on the wiki.
--> https://www.openstreetmap.org/changeset/178474021
--> https://wiki.openstreetmap.org/wiki/DE:OpenRailwayMap/Tagging_in_Switzerland#269%E2%80%93271_Neigungsanzeiger

Edit: I also found one signal in Serbia (https://www.openstreetmap.org/node/3147717739) tagged with railway:signal:incline.
--> https://www.openstreetmap.org/changeset/178473361

Both the distance and length subkey are fine for me, although strictly speaking length makes more sense.