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

Martin Atkins mart at degeneration.co.uk
Sun Apr 14 15:02:48 UTC 2013

On 04/14/2013 06:02 AM, Rovastar wrote:
> Now I started looking at trams and lightrail I see more of a need of
> consistent standards.
> They seem to be used interchangeably in San Fran and in Portland which was
> quoted a good example in the US most (nearly all) of what I would call tram
> lines are tagged light_rail with some tagged as trams lines spurring off and
> joining them at them at some points.
> Does anyone know of a reason for this? Are they generally and/or technically
> considered "trams" or "Light Rail" in the states?
> Now there is no wiki defination at all of railway=light_rail. The more I
> look the more I realise how bad we are as a community for documentation.
> I consider light rail to be a mini railway and not on roads on tracks
> whereas trams in generally go on streets. I imagine wikipedia will say
> similiar.
> Any thoughts?

Yeah, I was struggling with this myself. San Francisco's vehicles 
actually behave like a mixture of subway, light rail and tram. (with 
light rail defined as "higher-standard tram system separated from 
highways", as it is on the wiki)

Colin Smale noted in a descendent message that tram/light_rail can also 
differ in signalling, and of course SF has various types here too: when 
the vehicles run along what used to be tram lines the driver is in 
complete control and obeys traffic signals -- sometimes distinct lamps 
but always connected to the rest of the intersection. In some newer 
sections the mere presence of a train gives it right of way over other 
traffic, as if there were a level crossing. And finally, when they 
traverse the main subway they suddenly become more like subway trains 
and have an automatic train control system with moving block signalling[1].

The original mapper of SF rail tagged everything as light_rail, but as 
an experiment yesterday I re-tagged one of the lines as a tram -- at 
least, as much of it as I could get away with without affecting other 
lines and while making it all trivially revertable.

For what it's worth, the local transport agency tends to refer to this 
class of thing as "light rail vehicles", and I think if you consider the 
vehicles rather than the rails then that's fair, though prevailing 
discussion on the wiki suggested to me that we should tag based on the 
characteristics of the rails rather than of the vehicles, which for me 
makes *sections* of SF's rail network be classified as tram tracks.

Just to throw in one further complication, San Francisco's transport 
agency also operates more traditional trams[2] but every day they 
traverse some of the tracks used by the light rail vehicles, and in one 
section there's even a pair of platforms at each station to enable 
high-platform boarding of the light rail vehicles but ground-level 
boarding of the trams... further fodder, I think, for ignoring the 
vehicles and concentrating on the rails.

[1] To prove it, here's a real-time image of the state of the main subway:
The rest of the network is not controlled to nearly this level of detail.

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