[OSM-talk] Ways on bus route relations

Frederik Ramm frederik at remote.org
Sun Jun 15 19:53:53 BST 2008


Hi,

> Do the "ways making up the route" (as defined on Relations/Routes
> proposal) must be actual highway-tagged ways

Yes.

> or they may be distinct
> (maybe untagged) ways drawn over the highway ways?

To re-use a popular exclamation of the last few weeks: "Ye gawds no!" ;-)

> I am asking that because on some streets there may be many different bus
> routes going through it with different entry/exit points. If the ways
> making up the bus route must be the actual highway ways, those streets
> will need to be splitted on many tiny little ways, so that each section
> will belong to a different set of route relations. Did I understand it
> correctly?

Yes. This is somewhat of a shortcoming but that's the way it is 
currently done.

> Being able to draw a separated way for each bus route instead of splitting
> the highways on small segments would avoid this, but I don't know if it
> would be recommended.

No.

> Do you have other suggestions on how to avoid splitting the highway ways
> into small pieces on those cases?

There are some options. One would be to wait until we have ordered 
relations and then include not only ways, but also nodes, in an 
alternating fashion: "This route goes from point A using way B to point 
C then using way D to point E then ...". This is not currently possible 
because the server does not guarantee an order (you'd have to use the 
role attribute for this - from1=A,using1=B,from2=C,using2=D,from3=E...).

Or you simply ignore the fact that the bus route does not use the full 
length of the way; it would still be possible algorithmically to find 
out which part of the way the route uses (except from circular road 
layouts). Won't look nice on today's renderers but who says they cannot 
be improved?

A third option would be inventing a special kind of relation that's 
called a "way section"; it would contain the start node, end node, and 
way and model that part of the way that lies between the two nodes. Then 
make your bus route relation use these way sections as members wherever 
the bus route doesn't use the full way. But this would also be something 
new and not yet supported by renderers.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"




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