[Talk-us] Separate relations for each direction of US & State highways.

[Peter Davies]

Last night I wrote a long discussion of why I think we need to show the
cardinal directions of both OSM forward and OSM backward for 2-way ways
that serve both route directions in relation member roles.

In particular I argued for the use of two different symbols for two use
cases: one where the tag value is compound, like "east:unsigned" or
"north:express", and the other where there are two values to convey, e.g.,
"east;west" meaning OSM forward on this way is posted "east" and OSM
backward on this way is posted "west".

On further reflection, I think Martijn's pipe symbol example for an ordered
list of lane speeds, e.g., "60|60|40" across Lane 1, Lane 2, and Lane 3,
also applies to my wish to show the posted cardinal direction on a 2-way
single carriageway. Thus, "east|west" would mean that the OSM forward
direction lanes are posted "East" and the OSM backward direction lanes are
posted "West."

Combined with the use of the colon for compound values, we would have
examples like

"east:unsigned|west:unsigned"
"north|south:unsigned"
"north|east"

The two symbols are visually distinctive for human readers, and this also
would continue the practice of using the pipe symbol to represent lanes or
sets of lanes on a roadway.

On the Kennedy Expressway (I 90;I 94) out of Chicago, I think the three
carriageway roles might be

"east"
"reversible:east|west"     This would indicate that OSM foward serves as
"east" at times, and ODM backward serves at other times as "west".
"west"

Currently the median express lanes are coded with roles "reversable".

If the central carriageway ways were to use OSM forward as westbound, I
would suggest that they should ideally be swapped around, or otherwise
coded as "reversible:west|east".

****

Earlier I had conflated the "Ike" / Eisenhower Expressway (I 290) with the
Kennedy Expressway (I 90;I 94).  Sorry.

Peter


On Wed, Dec 18, 2013 at 1:46 PM, Wolfgang Zenker
<wolfgang at lyxys.ka.sub.org>wrote:

> Hi,
>
> * Martijn van Exel <m at rtijn.org> [131218 20:46]:
> > I am having second thoughts on the colon separator for
> > role=north:unsigned. The colon separator seems to be more common in
> > keys, like lanes:forward=2, lanes:backward=2 etc. while the semicolon
> > or pipe seem to be more prevalent to separate values. The pipe
> > character seems to be more widely used when there is an ordered set of
> > elements, like lanes:maxspeed=40|60|60 to indicate speed limits for
> > lanes 1,2,3 respectively, whereas the semicolon seems to be used as a
> > more generic separator like destination=Salt Lake City;Reno. (Even
> > there you could argue that there is an ordering, the first element
> > would appear first on the sign, the second one below that.)
>
> > So I changed the wiki
> >
> http://wiki.openstreetmap.org/wiki/Highway_Directions_In_The_United_States
> > to reflect this and propose the semicolon approach:
>
> > role=north;unsigned.
>
> > OK?
>
> the semicolon is usually the separator that you use if you have several
> unrelated values that unfortunately share the same key; I would interpret
> "role=north;unsigned" as 'this object has both the tags "role=north" AND
> "role=unsigned"'. I recommend staying with the colon approach, because
> we don't want to express two separate independent roles but the role
> "north" which happens to be of the "unsigned" version in this object.
>
> Wolfgang
>
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