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

80hnhtv4agou at bk.ru 80hnhtv4agou at bk.ru
Sun Aug 9 16:04:46 UTC 2020


in the chicago area we have 3 railway company’s operating the system, and one had signs left up from the old days
 
which in watching the train come into the stations platform  did not stop at the sign based on the number of cars + the
 
diesel engines or engines. which could be 5, 6, 7, or 8 cars, we stop at 8 here. 1 or 2 engines.
 
to that end a california editor tagged all 200+ stations with the stop tag that is 400 + unverified platforms.
 
i would say more but you people do not like that.
 
with no checks and balances, editorial board etc. they will stay there forever.
 
>Sunday, August 9, 2020 9:40 AM -05:00 from Alexey Zakharenkov < a-zakh at yandex.ru >:
> 
>As a person who have been monitoring and fixing rapid transit networks (primarity subways) for long I can say that railway stop_positions make more headache than advantage. Most of stop_positions look like here:  https://www.openstreetmap.org/relation/7966822#map=19/35.70290/139.74568
>i.e. they reside on rails near the station node (adding no information) and carry bunch of station's tags like wikipedia and name translations (adding info duplication or triplication). Mappers' eagerness to conform PTv2 in respect of adding stop_positions here and there results in many errors:
>*) stop_positions are created and not added to stop_area relations
>*) stop_positions are erroneously converted to stations and vice versa
>*) stop_position tags are transferred to another nearby node ignoring its membership in routes and stop_areas
>*) stop_position duplicates corresponding railway station object (public_transport=stop_position + railway=station)
>*) and so on.
> 
>All this makes subway maintenance (in state that allows routing) tenfold costly.
> 
>BTW, I could not find the definition where is the point of stop of a 150-meter train. In practice, the position of head or center is used.
> 
>Best regards,
>Alexey
 
> On 8. Aug 2020, at 14:26, Jo <winfixit at gmail.com> wrote:
> 
> You could add all.

WRT mapping the stop position I agree that adding them all would make sense. For the connection  
relation I believe it is not manageable to record and maintain this level of detail, and the 
practical gain is very limited because of dynamic variations in every day operations 
(might vary according to the railway company, maybe somewhere this is more stable).

Cheers Martin 
> 
> 
>08.08.2020, 03:55, "Andy Townsend" < ajt1047 at gmail.com >:
>>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.
>>
>>As I asked on the changeset that added the one above
>>https://www.openstreetmap.org/changeset/40603523 , how should these be
>>mapped and how should the PTv2 relations be set up for the different
>>services that use them, given that different train services will use
>>different stop locations here depending on train length?  Should each
>>stop position be mapped and should there therefore be different copies
>>of each relation for all the possible train lengths?  Should a "pretend"
>>average stop position be added which is actually never correct but will
>>at least look nice to data consumers that use PTv2 data?  Given that we
>>don't know the actual stop position perhaps the railway=station object
>>(in this case  https://www.openstreetmap.org/node/7154300845 ) should be
>>used instead?
>>
>>Maybe the public_transport=stop position should be omitted entirely? 
>>This last option seems extreme, but one reading of
>>https://wiki.openstreetmap.org/wiki/Tag:public_transport%3Dstop_position
>>where it says "However, marking the stop position adds no information
>>whatsoever when it is placed on the road at the point closest to
>>highway=bus_stop or on the tram tracks closest to railway=tram_stop. In
>>that case it can be abandoned. " might actually support that (and that
>>seems to be the view of one side of the argument in the USA).
>>
>>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.
>>
>>Best Regards,
>>Andy
>>
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