[Talk-transit] Multiple tracks

Roger Slevin roger at slevin.plus.com
Mon Jun 22 10:45:29 BST 2009

As someone who doesn't have the experience of mapping that you all do, but I
do know something about public transport, I can see how the various concepts
for single track and double track etc work along straightforward corridors
(note these must be "tracks" (or maybe some other term) and not "lines" - as
a "line" in public transport is something completely separate from the
infrastructure) ... but what happens when operational details get more
complicated ... at stations, or near and in depots and sidings?  What
happens for passing bays?  Does a track have a directionality associated
with it (even if it is only implied by a national convention of "driving on
the left/right"... though that will give some issues on the German border
where operations switch sides) - and what happens when multiple tracks are
signalled for bi-directional working?

I sense that there is a potential issue here between describing the physical
infrastructure and describing its functional performance ... and I am not
sure the boundary has been drawn correctly between the two.


-----Original Message-----
From: talk-transit-bounces at openstreetmap.org
[mailto:talk-transit-bounces at openstreetmap.org] On Behalf Of Peter Miller
Sent: 22 June 2009 10:31
To: Jochen Topf
Cc: osm
Subject: Re: [Talk-transit] Multiple tracks

On 22 Jun 2009, at 07:51, Jochen Topf wrote:

> On Sun, Jun 21, 2009 at 05:09:35PM +0100, Richard Mann wrote:
>> No, simpler than that:
>> tracks=1 => render a single line at all zooms
>> tracks=2 => render a double line at all zooms
>> tracks=X => render a multiple line with X tracks at all zooms
>> tracks=1ofX => render a single line at high zooms, but render as if  
>> tracks=X
>> at medium/low zooms
> But then you'd still draw several lines nearly on top of each other  
> in medium
> zoom levels which doesn't look good, which was the problem we were  
> trying to
> fix?
> Anyway, this is a rather specialized trick about rendering the  
> number of tracks
> properly. But what if you want to render other attributes. Say one  
> of your two
> tracks is an industrial railway, the other a normal passenger  
> railway and you
> want to distinguish those types. On medium zoom levels, is this a  
> two track
> thing and we loose the type distinction, or do we keep it?

The dual_carriageway and Junction relations would appear to the a good  
way of doing such things. I realise that the 'dual carriageway' term  
is not right and that other work would be required on the  
specifications, however it would seem a better starting point.


A group of parallel tracks would be combined using 'dual carriageway'  
and then a group short sections of track and nodes can be combined as  
a 'Junction'. The render would then have a choice of drawing modes,  
either a single line and single point, or multiple lines/points.



> Jochen
> -- 
> Jochen Topf  jochen at remote.org  http://www.remote.org/jochen/   
> +49-721-388298
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