[Tagging] Blatant tagging for the renderer: bridges & abandoned railways

moltonel 3x Combo moltonel at gmail.com
Tue Mar 10 14:37:45 UTC 2015

On 10/03/2015, Bryce Nesbitt <bryce2 at obviously.com> wrote:
> On Mon, Mar 9, 2015 at 5:53 PM, moltonel 3x Combo <moltonel at gmail.com>
> wrote:
> I've also seen the opposite mapping issue, where an abandoned railway was
> deleted from the map,
> when in fact large chunks still exist.

If an osm way represents a railway that is 50% gone, is it more
correct to keep the way or to delete it (ignoring the actually-correct
but time-consuming task of deleting only the parts that are gone) ?
Where would you put the "% gone before complete deletion is justified"
threshold ? Throw in the problem that "gone" is a subjective term
(plus different answers on the ground and using imagery), and you get
a nice recipe for disagreements.

I'm playing the devil's advocate a bit here, to show how quickly
opinions can diverge. Please always discuss your intent with the other

Thankfully the distinction between abandoned and disused is clear.
It's between abandoned and razed/not_maped that things get tricky.

>> Also, if an abandoned railway has evolved into something else, then
>> it's not an abandoned railway anymore. If you add a highway=cycleway
>> tag, you should remove the railway=abandoned tag.
> I don't see that railway=razed damages highway=cycleway.

s/razed/abandoned/. No damage done, it's just no longer usefull.

> The present day cycleway may well have photos of that same old railway on
> interpretive signs.  The current cycleway may in fact be called a "rail to
> trail".  Some people seek those out explicitly, because they're associated
> with a flat grade and gentle curves.
> In cases like this the history is* a part of a present day object.*

Railway=* is a poor heuristic for flat grades and gentle curves : lots
of false negatives. If the cycleway is advertised as a 'rail to
trail', it'll transpire in other tags, name=* and maybe tourist=*.

I'm not saying that the attributes you describe are not interesting,
but that describing them by tagging the history of the object is the
wrong way around. Tag the current state, not how it came to be. Just
like we tag smoothness=* rather than the name of the road surfacing
company (yeah, silly example).

> Railroads are special in part because they're large and long, far bigger
> than any abandoned shop or razed cottage.
> They leave a major footprint on the future world, one that's often apparent
> well after the last bit of gravel is dug out and planted over.
> It's more like tagging "shoe shop in a landmark beaux arts former post
> office" than "turn left where the fruit stand used to be".

Yes, railways do leave long-lasting signs. Then again, even cow paths
have a tendency to turn into avenues (with a tell-tale layout
appreciated by historians and tourists) given enough time, so it's not
particularly unique or impressive. Yet when it comes to tagging the
past, OSM apparently only cares about railways.

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