[Talk-us] Rewriting route direction documentation to emphasize subrelations

[Tod Fitch]

I don’t have a good feeling about how the whole country is, but all the freeways I have looked at in California have three relations (1 master and one each for the cardinal direction). In my area the US routes are mostly but not all using three relation scheme as are a few California state routes. At least for my editing style using JOSM, I much prefer the super/sub relation scheme as I find it easier to fix things when broken.

—Tod

> On Jul 31, 2021, at 6:19 AM, Clifford Snow <clifford at snowandsnow.us> wrote:
> 
> Do you know what portion of the Interstate system has been mapped with route directions? What about US routes?
> 
> Clifford
> 
> On Fri, Jul 30, 2021 at 11:37 PM Minh Nguyen <minh at nguyen.cincinnati.oh.us <mailto:minh at nguyen.cincinnati.oh.us>> wrote:
> The article has been rewritten according to the draft and renamed to
> reflect signage and tagging practices in Canada and New Zealand as well:
> 
> https://wiki.openstreetmap.org/wiki/Route_directions <https://wiki.openstreetmap.org/wiki/Route_directions>
> 
> Vào lúc 17:55 2021-07-24, Minh Nguyen đã viết:
> > Back in 2013, a discussion on this list [1] led to a wiki article
> > documenting how to indicate the cardinal direction along a route, such
> > as the "north" in northbound I-75. [2] I've drafted a rewrite of this
> > article at [3] and would like to get the community's feedback on it
> > before touching the original, which has often come up in discussion. The
> > rewrite attempts to clearly explain route directions for both domestic
> > and international audiences. These days, overseas mappers are very
> > active in navigation mapping, and route directions are also relevant to
> > some non-English-speaking regions.
> >
> > According to the original documentation, setting relation roles to
> > cardinal directions is preferred over creating a separate relation for
> > each direction and setting direction=* to the cardinal direction (and
> > joining the relations in a superrelation). The rewrite reverses this
> > guidance, placing more emphasis on subrelations and superrelations than
> > relation roles.
> >
> > The directional roles have had the advantage of being easier to
> > introduce than superrelations, especially for routes that only
> > occasionally run along divided highways. That was important early on,
> > when route relations were first being built out. However, it has tended
> > to result in routes that are only partly tagged with cardinal
> > directions, requiring data consumers to infer the cardinal direction
> > along ways with forward, backward, or unset roles. Additionally, editors
> > and quality assurance tools have not added specialized support for these
> > roles as they have for forward/backward, so existing coverage has been
> > fragile.
> >
> > Although subrelations and superrelations are initially more difficult to
> > create, they are easier to maintain in the long run and are already
> > well-established for major road routes as well as public transportation
> > routes. I see them as part of a natural progression in OSM towards
> > greater detail, coverage, and structure.
> >
> > This would only be a rewrite of documentation. I'm not proposing an
> > effort to systematically restructure existing route relations into
> > subrelations and superrelations. However, this documentation would
> > better support mappers who are interested in carrying out such
> > improvements themselves. Thanks for your attention.
> >
> > [1]
> > https://lists.openstreetmap.org/pipermail/talk-us/2013-November/thread.html#12165 <https://lists.openstreetmap.org/pipermail/talk-us/2013-November/thread.html#12165>
> >
> > [2]
> > https://wiki.openstreetmap.org/wiki/Highway_Directions_In_The_United_States <https://wiki.openstreetmap.org/wiki/Highway_Directions_In_The_United_States>
> > [3] https://wiki.openstreetmap.org/wiki/User:Minh_Nguyen/Route_directions <https://wiki.openstreetmap.org/wiki/User:Minh_Nguyen/Route_directions>
> 
> --
> minh at nguyen.cincinnati.oh.us <mailto:minh at nguyen.cincinnati.oh.us>
> 
> 
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