[Tagging] PTv2 public_transport=stop_position for stop positions that vary based on train length

Warin 61sundowner at gmail.com
Mon Aug 10 07:20:08 UTC 2020

On 8/8/20 10:54 am, Andy Townsend wrote:
> Hello,
> This is a question that actually arose out of a "how to tag" argument 
> that's come to the attention of the DWG in the USA, but it's actually 
> easy to describe in terms of data in the UK that I'm familiar with, so 
> I'll do that.
> https://www.openstreetmap.org/node/12004813 is a 
> "public_transport=stop_position" for a local station and is part of 
> https://www.openstreetmap.org/relation/6396491 among other relations.  
> The problem is that train lengths vary, and there are a number of stop 
> positions, each of which are actually signed on the platform for the 
> benefit of the drivers.  From memory I think that there's at least a 
> 2-car stop, a 4 car stop and 6/8 and 10/12 car stops.  The problem is 
> that the current node doesn't correspond to any of them.

Why is the front of the vehicle (bus, train, ferry.. and possibly 
others) mapped?

Would it not be better to map the thing most usefull to most people? 
That would be where passengers get on/off, on multiple exit vehicles 
like train then the average of these positions could be used.

Trains here of varying lengths tend to place the middle of the train at 
the middle of the platform - thus it is consistent for any train length. 
The only exceptions are where the platform is shorter than the train so 
the train stops such that the designated car/carriage is centered on the 
platform - thus it is still a consistent location for OSM.

> Maybe the "correct" answer is none of the above?  With a "local 
> mapper" hat on I've managed to avoid PTv2 since it basically isn't 
> relevant anywhere I normally map things, largely because I don't tend 
> to do that near any actual public transport infrastructure, but with a 
> DWG hat on I haven't been able to avoid the question, hence me asking 
> here.

I have mapped a few bus routes and 'corrected' some PTV2 trains... but 
I'd not hold them up as 'best' examples... only ones that are 'better' 
than what was there before and probably the simplest way that I could 
see to do it.

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