[Tagging] Cartpath RFC

Minh Nguyen minh at nguyen.cincinnati.oh.us
Tue Jan 5 07:59:36 UTC 2021

Vào lúc 02:45 2021-01-03, Jean-Marc Liotier đã viết:
> Sticking to a subtag of highway=service (such as highway=service + 
> service=golf_car_path) will bring graceful degradation: applications 
> aware of service=golf_car_path will take it into account while those 
> that are not will still render highway=service. Tagging 
> highway=golf_car_path will leave most applications unable to make sense 
> of that rare value.

The key word there is "render", but there are other, non-rendering data 
consumers that have shown us that the degradation isn't so graceful. [1] 
If highway=service were a relatively young tag, that would be one thing, 
but the ecosystem around OSM has already gotten used to service roads 
falling within a certain range of possibilities.

If backwards compatibility is the a consideration, then we need to weigh 
two competing challenges:

* That by adopting a new highway=* value, outdated renderers lose out on 
a tagging style that has only been around for less than two years [2], 
before which there was no reliable way to tag or render golf cart paths.

* That by incorporating highway=service, outdated routers continue to 
direct people into unsafe situations due to tagging semantics that have 
been documented for over 13 years. [3] For example, OSRM's inferred 
access restrictions for service road types haven't changed in over four 
years [4], and there's no guarantee that deployments will update 
promptly if there's a patch.

In an ideal world, there would be satnav warning signs [5] all over the 
place and drivers would heed them. In an even more ideal world, OSM 
would have robust processes in place to keep software developers in the 
loop and deployments up-to-date with regard to the latest changes to 
tagging conventions. But since we're left wanting on both fronts, I 
think a new highway=* value is at least worth consideration.

[2] https://github.com/openstreetmap/iD/issues/6165
[3] https://wiki.openstreetmap.org/wiki/Special:PermanentLink/44789
[4] https://github.com/Project-OSRM/osrm-backend/pull/2808

minh at nguyen.cincinnati.oh.us

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