[Tagging] Feature Proposal - RFC - More Consistency in Railway Tagging

Martin Atkins mart at degeneration.co.uk
Sat Apr 13 16:36:44 UTC 2013


On 04/13/2013 04:54 AM, Rovastar wrote:
>
> As San Fran doesn't look like it has many railways I suggest you look at
> locations around the world maybe UK that has a detailed rail infrastructure
> so you get a better understanding about how it is done there.
>

Yes, I have looked at examples from elsewhere too; several of the 
examples in my proposal are actually from the UK.

The only consistent thing I see with railway tagging, regardless of 
where I look, is inconsistency.

To pick some examples from places I've lived or visited and am familiar 
with:

- The tramway along Damrak in Amsterdam is a two-way tramway in the 
middle of the street, just like my San Francisco examples. The tramway 
is a separate way from the highway here. However, elsewhere in 
Amsterdam, Ferdinand Bolstraat is a single way with both 
highway=unclassified and railway=tram .

- In Greater London, the London Underground Metropolitan Line crosses 
the LU Central Line and the Chiltern Main Line. All three of these 
railways are represented as one-way-per-track, which causes the data to 
suggest that the metropolitan line crosses under eight separate bridges, 
when in reality it's just two wide ones. Arguably this is a problem with 
the tagging scheme for bridges rather than for railways, but still.

- Continuing down the same line (pun intended!), at Finchley Road 
(heading towards central London) the Metropolitan Line and the Jubilee 
Line part ways in two separate tunnels, each with two tracks. The 
Jubilee Line is tagged as a single way representing the entire tunnel 
and both tracks, while the Metropolitan Line is tagged as two ways. I'd 
argue that it's sufficient to tag both as a single way, but if either 
one were to be separated it seems like the Jubilee Line is a better 
candidate, since it's a pair of narrow tunnels created with a tunneling 
machine, while the Metropolitan Line is a cut-and-cover pair of tracks 
running side-by-side in a wide tunnel.

- Moving on to England's main-line railways, the Great Eastern Main Line 
is tagged as a pair of ways from London to Whitham, but then it 
inexplicably becomes a single way at least as far as Manningtree (I 
didn't look any further, because I've never traveled past this point and 
so I have no idea what the railway looks like on the ground.)

So all that is to say that I think we're far from having a standard for 
tagging railways in Europe, too.

First and foremost I believe that more standardization would be 
beneficial to make the data more useful; currently the wiki says very 
little about how railways are to be tagged outside of talk pages and 
off-hand comments, and that leads to inconsistencies.

Secondarily I think OSM mapping should always *begin* with a simple 
ground transportation network (of highways, railways and waterways) and 
then build upon that with additional (optional) tagging schemes to add 
the level of detail that desired for more detailed rendering at close 
zoom levels and for less-common usecases like modeling the detailed 
operational details of a railway, both without conflicting with the 
basic use-case of a geo-spatial route graph.

My proposal achieves the simple network and *begins* the detail, leaving 
the door open for an interested party to continue it to whatever degree 
of detail the community finds useful, hopefully in a way that is 
compatible with approaches to also map highways and waterways in detail.





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