I am writing this to clarify what is the OSM approach to mapping – do we map things from real life as they are (beautiful or not), or do we map the things are they should be in perfect world (so it is our projection, or wishes for the world)?
The question is triggered by one place, which if I remember correctly is subject to edit, removal, edit, removal, and this is because there is path which should not exist (because it is dangerous and illegal), yet it exists and it will exist for sure, because simply life finds it ways to avoid shortcomings of local authorities.
I am in the camp, that such path should be mapped, because it simply exists, people are using it, it is visible (grass is trod down). The other camp obviously does not share my opinion, and I just found out the path was deleted because “it is illegal”. Of course it is deleted in OSM, not in real life.
There is yet another angle for it: thanks for the mapper who added such path in other place I was able to get to my destination in timely fashion. Same case – formally path is illegal, dangerous, and yet ton of people is using it because it is useful.
So… what is the guideline here?
Background info (in those cases): it is about “wild” railway crossing (on foot), but the question is in general sense.
We map reality as it is. For example, fact that road or building exists illegally is not a valid reason to delete it from map. We have a lot of such illegal objects mapped and it is fine. In fact, OSM was used as supplemental data source for Silesian flood planning because it contained also illegally build houses missing from official maps.
Though access=foot=bicycle= are legal access tags - so even if everyone openly ignores cycling ban it is still bicycle=no (or no bicycle tag, depending on exact case)
Assuming that it is illegal to use it and path exists there: highway=pathaccess=no - maybe also hazard= of some kind.
I added this documentation to wiki some time ago, and as I far as I know this represents current consensus.
If it is about place in Poland on active rail tracks: such wild crossings are definitely illegal, even if not specifically signed as illegal.
If it is about crossing without path: not really mappable, I think.
Let us know if problem reoccurs or if that mapper makes this mistake on more systematic scale. Or you need help with reverting such deletions.
Regarding illegal (social, use, etc.) trails, the US OSM community has a group working with Federal land managers to come up with a tagging scheme that is acceptable to both the “it’s illegal and shouldn’t be mapped” and “it exists so we will map it” viewpoints. Representatives of two hiking apps popular in the US (Gaia and AllTrails) have had representatives involved and are, I believe, modifying their apps to account for the suggested tagging to either hide or deemphasize trails that are not desired by the land manager. You may want to read the recommendations at United States/Trail Access Project - OpenStreetMap Wiki
Note that it appears to not be about cases where there is actual path across rails.
And in such case mapping it properly with access=no reduces risk of someone mapping it without access restriction, has some uses like documenting cases where crossing are - which can be useful to diagnose missing legal crossings and in some cases may be sadly needed for actual use where next legal crossing is kilometres away.
And many arguments there apply only to not mapping nonexisting paths (which is a good idea in general, not only on rails, maybe with some rare exceptions).
I switched camp from “map everything” to “don’t map” regarding small paths made by wildlife, mapped, and then attracting people to go there, eventually by mountainbike and hinder and destroy wildlife.
For those small paths that really exist I say: don’t map them.
This is in the Netherlands where nature is under extreme pressure.
The informal=yes tag may also be useful here. This tag signifies that the feature was not intentionally created. While primarily used for pedestrian paths, it can also be applied to other types of features. A common example of an informal footpath is a “desire path.”