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

[Minh Nguyen]

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

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 
> 
> [2] 
> https://wiki.openstreetmap.org/wiki/Highway_Directions_In_The_United_States
> [3] https://wiki.openstreetmap.org/wiki/User:Minh_Nguyen/Route_directions

-- 
minh at nguyen.cincinnati.oh.us